ISO \Y b H- H A HISTORY OF PSYCHOLOGY Digitized by the Internet Archive in 2017 with funding from Duke University Libraries https://archive.org/details/historyofpsychol01klem A HISTORY OF PSYCHOLOGY BY OTTO KLEMM EXTBAOBDINABY PBOFESSOB OF PHILOSOPHY IN THE UNIVEBSITY OP LEIPZIG AUTHORIZED TRANSLATION WITH ANNOTATIONS BY EMIL CARL WILM, Ph.D., LL.D. PBOFESSOB OF PHILOSOPHY IN WELLS COLLEGE AND LECTDBEB IN PHILOSOPHY AT BBYN HAWB COLLEGE FOB 1914-15 AND RUDOLF PINTNER, Ph.D. ASSISTANT PROFESSOR OF PSYCHOLOGY IN THE OHIO STATE UNIVERSITY 70 , 3 2 8 CHARLES SCRIBNER’S SONS NEW YORK CHICAGO BOSTON Copyright, 1914 , by CHARLES SCRIBNER’S SONS A PREFACE FOR THE ENGLISH EDITION The following work is a translation of Professor Edemm’s Geschichte der Psychologie, which constitutes Volume VIII of the now widely known series “Science and Hypothesis.” As a searching study of an enormously wide and difficult field the original German work has already won for itself an es- tablished place in the recent literature of the subject, and it is confidently believed that the qualities which have given the original work its deserved popularity, the author’s equally firm grasp of the most widely separated psychological epochs and tendencies, his admirable attention to both the specu- lative and the scientific aspects of psychology, and, finally, the relative prominence given to recent and experimental psychology, will at once commend the work to the large number of workers in modern psychology to whom English works of just this type have heretofore not been available. The work of translation has been about equally divided between the two translators, Chapters I-VI, inclusive, having been executed by myself, and Chapters VII-XII, inclusive, by Doctor Pintner, and each translator is solely responsible for the final form in which his own part of the work appears. I wish to express my cordial acknowledgments to Pro- fessor Miinsterberg, to whose friendly suggestion the plan for this translation owed its first inception, and to Professor Titchener for a number of valued suggestions on terminology. Bryn Mawr College, Bryn Mawr, Pa., October, 1914. E. C. WlLM. DO AUTHOR’S PREFACE FOR THE ENGLISH EDITION In the autumn of 1911 I received a letter from Doctor Wilm informing me that at the suggestion of Professor Munsterberg he was maturing plans for an English trans- lation of my History of Psychology, and requesting my co- operation. I very gladly granted him permission for such an undertaking, and I have since then had much pleasure, as different parts of the translation have come to me, in seeing how completely he and his excellent collaborator, Doctor Pintner, have overcome one after another the mani- fold difficulties which such a translation presents. The present English edition is making its appearance under quite different circumstances from those which pre- vailed when the original German edition went into print. I make reference in the course of the book to the irregular development of psychology. The history of psychology seems to be undergoing a development of a similar sort. Although the triumphant advance of the experimental method has for some time obscured the connection of modern de- velopments with the earlier epochs of our science, there has recently appeared a whole series of comprehensive works on the history of psychology to which the valuable additions to my own bibliography made by the English editor bear testimony. The history of psychology has thus itself be- come a problem. With the varied treatment, however, which such a wealth of material permits, one of these works is not likely to crowd out another, but rather to supplement vii viii AUTHOR’S PREFACE FOR ENGLISH EDITION and enhance it. No one, in any case, is more clearly aware than I that my own selection and arrangement of the material are partly determined by the present position of psychology in my own country. I do not, indeed, see how it could be otherwise in the case of a historical presentation which itself extends directly into the present. May I hope, then, that my little book will also find read- ers beyond the sea who will follow in it the fortunes of psy- chology among its sister sciences in western Europe, and that Doctor Wilm will thus find himself repaid for the trouble and care for which I am myself permanently indebted to him ! Otto Klemm. Leipzig, June, 1914. CONTENTS INTRODUCTION PAGE 1. General Characteristics of the History of Psychology 1 2. Plan of the Present Work 2 3. Modern and Ancient Elements in Psychology .... 6 4. Literature 8 Translators’ Note on English Literature 10 PART I GENERAL TENDENCIES OP PSYCHOLOGY I. METAPHYSICAL PSYCHOLOGY Chapter I. Dualism in Psychology 1. Relation of Metaphysical and Empirical Tendencies . 12 2. Dualistic Psychology 14 Chapter II. Monism in Psychology 1. Spiritualism 26 2. Materialism in Psychology 32 (a) Atomistic Materialism . 33 ( b ) Mechanistic Materialism 36 (c) Psychophysical Materialism 38 IX X CONTENTS II. EMPIRICAL PSYCHOLOGY Chapter III. Descriptive Psychology PAGE 1. Period of Pre-Scientific Concepts : The Doctrine of Mental Faculties 44 (a) The Doctrine of the Parts of the Soul 46 (b) The Beginnings of Empirical Psychology in Scholasticism 50 (c) The Psychology of the Renaissance 56 ( d ) The Newer Faculty Psychology 58 2. The Psychology of the Inner Sense 69 (a) The Older Doctrine of the Inner Sense 72 ( b ) The Inner Sense as an Independent Source of Experience 76 (c) The Relation of Inner Sense to Epistemological Problems 82 Chapter IV. Explanatory Psychology 1. Association Psychology 87 (a) The Early Beginnings of Association Psychology ... 88 ( b ) The Dominance of the Concept of Association .... 92 .2. Psychology as a Mechanics of Ideas 103 3. Comparative Psychology Ill (a) Ethnic Psychology Ill ( b ) Animal Psychology 113 (c) Influence of Darwinism 115 (d) Individual Psychology 117 4. Influences of Natural Science 119 (a) The Newer Phrenology 119 (b) The Influence of Sense Physiology 123 (c) Experimental Psychology 127 CONTENTS XI PART II DEVELOPMENT OF THE FUNDAMENTAL CON- CEPTS OF PSYCHOLOGY Chapter V. The Idea of Psychology as a Science PAGE 1. Older Conceptual Formulations of Psychology . . . 147 2. The Problem of a Science of Psychology 150 3. The Modern Concept of Psychology 155 (a) Psychology and Philosophy : Psychologism and Its Opponents 156 ( b ) Psychology and Natural Science : Differentiation of Physical and Psychical Phenomena 159 Chapter VI. The Subject-Matter of Psychology: Consciousness 1. The History of the Concept of Consciousness . . . 166 (а) Early Developments of the Concept 166 (б) Development of the Modern Concept of Consciousness . 169 2. The Concept of the Unconscious 172 (a) Representatives and Opponents of the Notion of the Unconscious 172 (b) Arguments for and against the Unconscious 175 3. The Range of Consciousness 181 4. The Graduation of Consciousness : Attention .... 184 Chapter VII. Classification of the Contents of Consciousness 1. Survey of the Most Important Principles of Classi- fication 191 (а) The Rise of Psychological Classification 192 (б) The Principle of Non-Deri vability 194 (c) The Principle of Intentional Relationship 200 (d) The Principle of Analysis 202 CONTENTS xii PAGE 2. Modern Forms of Classification 205 3. The Concept of the Psychical Element 210 Chapter VIII. Psychological Methods 1. Observation and Introspection 212 2. Physiology the Basis of Psychology 215 3. The Development of the Methods of Psychical Mea- surement 218 (a) The Older Forms of the Methods 220 (i b ) The Influence of the Theory of Error 222 (c) Connection with the Expression Methods 229 Chapter IX. Psychical Measurement 1. Early History of Psychical Measurement 232 (а) The Earliest Suggestions of Psychical Measurement . . 233 (б) Weber’s Law and Its Preliminary History 235 2. The Founding of Psychical Measurement by Fechner . 242 3. Discussions Arising out of Fechner’s Psychophysics . 245 (а) Objections and Attacks 245 (б) Fechner’s Reply 252 (c) Some Philosophical Opponents 254 4. The New Foundation of Psychical Measurement . . 257 (a) G. E. Muller’s Foundation of Psychophysics .... 257 (b) The Psychological Interpretation of Weber’s Law . . . 262 CONTENTS xiii PART III A HISTORY OF THE MOST IMPORTANT PSYCHO- LOGICAL THEORIES Chapter X. Theories of Sensation PAGE 1. General Theories of Sensation 271 (a) The Older Theories 273 - (b) The Theory of Specific Energy of the Nerves .... 275 2. Theories of Vision 279 (a) Ancient Theories of Light 279 ( b ) Separation of Physical and Physiological Optics . . . 283 (c) Modern Color Theories 287 (1) The Three-Color Theory 290 (2) The Four-Color Theory : Opposition and Develop- ment 292 3. Theories of Audition 297 (а) Preliminary History of the Resonance Theory .... 297 (б) The Theory of Resonance 299 (c) Further Development of the Resonance Hypothesis . . 304 (d) Consonance Theories 308 Chapter XI. Theories of Spatial Perception 1. The Natural Scientists of the Middle Ages .... 317 2. Some Special Problems 322 3. Nativism 326 (a) The Founding of the Theory by Johannes Muller . . . 326 ( b ) Its Transference to the Sense of Touch 327 (c) The Later Nativistic Theories 330 xiv CONTENTS PAGE 4. Empiricism 333 (a) The Origin of Empirical Theories of Space 334 (£>) Helmholtz’s Theory of Space 335 5. The Genetic Theories 337 (a) Herbart’s Fusion Theory 337 ( b ) Purely Psychological Theories 338 (c) The Local Sign Theories 340 (1) Lotze’s Theory 340 (2) Its Physiological Development 342 (3) Its Psychological Development 343 Chapter XII. Theories of Feeling and Volition 1. Theories of Feeling 346 (а) Phenomenological Presuppositions 347 (б) Intellectualistic Theories of Feeling 350 (c) Psychomechanical Theories of Feeling 352 (d) Physiological Theories of Feeling 355 (c) Psychophysical Theories of Feeling 358 2. Theories of Volition 359 (a) Intellectualistic Theories of Volition 361 (1) The Ancient Concept of Freedom 361 (2) The Primacy of Will or Intellect 362 (3) The Classical Period of the Problem of the Freedom of the Will 364 ( b ) The Absolute Theory of the Will 366 (c) Heterogenetic Theories of the Will 368 (d) The Emotional Theory of the Will 370 Index of Names 373 Index of Subjects 379 A HISTORY OF PSYCHOLOGY A HISTORY OF PSYCHOLOGY INTRODUCTION 1. General Characteristics of the History of Psychology A contemporary psychologist has said that psychology has had a long past but a brief history. Scattered reflec- tions on psychological questions indeed abound throughout the entire history of science, but the continuity of psycho- logical investigation has often been interrupted, while a really fruitful development of psychology belongs to very recent times. With this the extreme complexity of mental processes, a complexity which seems only to increase the more intimately we come to know them, has had no little to do. There is something in the very nature of mental processes, even in their simpler forms, which resists the attempt to subject them to scientific treatment. In the first place, they do not constitute a special group of facts which can be unambigu- ously distinguished from other groups of facts, and which perhaps have to be discovered. They are constantly with us; indeed, every fact is in part, or on one of its sides, a mental fact. Moreover, the facts of consciousness are not data which are discovered like a rare mineral or which can be observed like an unfamiliar phenomenon in nature. Long before these facts are subjected to scientific analysis they have been subjected to innumerable influences of social life. Language, for example, to mention only the most important 1 2 HISTORY OF PSYCHOLOGY of these influences, has already appropriated them, has de- scribed them, and has interpreted them according to the needs of practical life. There is a further peculiarity of the material of psychology which makes the scientific investi- gation of it especially difficult. In all scientific investiga- tion a certain emotional detachment would seem to be abso- lutely necessary for the success of the scientific enterprise. But in psychology the feelings and emotions become them- selves objects of investigation, and the most central questions of psychology are intimately related to the important inter- ests of our common life. It is true that even in the physical sciences the methods of investigation have only gradually been freed from the subjective interference of feeling. It is told of no less an observer than Galileo that he was so irri- tated by the inexplicable changes in the form of Saturn, due to the position of its rings, which were at the time still un- known to him, that he refused to observe this planet at all. How much more difficult must it be for psychology to fulfil the demands of purely objective observation when its funda- mental problems are so deeply interwoven with man’s deep- est interests, hopes, and passions! It is only a consequence of these circumstances that psychology has undergone a dif- ferent historical development from that of cognate sciences and that the historical account of its development must fol- low its own more or less unique methods . 1 2. Plan of the Present Work One of the most notable differences between the develop- ment of psychology and that of the other empirical sciences, particularly the natural sciences, lies in the relation between the two stages of development which we may call the prac- 1 Cf. Ebbinghaus, “Psychologie,” in Kuliur der Gegenwart, I, 6 2 , 1908, pp. 173 Jf. INTRODUCTION 3 tical and the purely observational or descriptive. Most of the sciences which we to-day class as descriptive sciences had as their original aim some sort of control over nature and fortune. Man does not at first observe the processes of nature in the midst of which he fives merely for their own sake; he rather observes them in order that he may himself influence and control them in the interests of his own needs . and purposes. Thus astrology, which sought to afford gui- dance in conduct through the prognostication of events, be- came astronomy; alchemy, which had as its object the arti- ficial production of precious metals, became chemistry, and so on. Following up this analogy, one would be led to look for the antecedents of modern psychology in chiromancy, in mnemotechnics, and in witchcraft, which plays such an impor- tant role even with so thoroughgoing an empiricist as Bacon. These occult sciences, however, which are obviously the ante- cedents of modern spiritism, have borne little or no relation to the scientific analysis of mental fife. It is true that we find in modern times many attempts to give explanations of spiritistic phenomena which lay claim to scientific status. Count Gasparin, for example, attempts to explain spiritistic phenomena by reference to a fluid, called “psychode” by Thury, which is subject to voluntary control. And between the wholly transcendental explanation of the astronomer Porro, with his hypothesis of a divided personality, and the pseudo-empirical view of Maxwell that spiritistic phenomena are to be explained by the collective consciousness of the participants in the psychic experiment, there is a whole series of more or less fantastic attempts to extend the concepts and categories of modern psychology to the realm in question . 1 But the transition from the practical to the purely observa- 1 The more important of these attempts at explanation have been compiled by Camille Flammarion in Unbekannte Naturhrafte; German translation by Michalski, 1908, p. 343. 4 HISTORY OF PSYCHOLOGY tional stage, so characteristic of the natural sciences, evi- dently does not repeat itself here. It is due to the very nature of the contents of consciousness that their scientific study has profited but little from contact with the species of practical psychology referred to above, and that such study could prosper only within the bounds of a world view in which theoretical motives predominate or in which, at any rate, practical motives are moderated by contact with ethical or religious needs and interests. Thus the meagre practical application of psychology which the his- tory of this science reveals would also find its explanation. While, then, on the one hand, scientific psychology owes little to the doubtful successes of the occult sciences, based upon an alleged knowledge of mental life, scientific psychology has, on the other hand, rather persistently declined to take any interest in the practical problems of the occult. The alliance which has for a considerable period been established between psychology and pedagogy seems, indeed, to promise well for the future. If psychology is ever to become a practical sci- ence it will become such by entering the fields of pedagogy, law, and medicine, fields which have, indeed, already been opened to modern psychology. And when one compares the success of psychology in these fields with the success of the natural sciences in their various applications, the com- parative recency of psychology as a theoretical science must not be lost sight of . 1 From these changes in the point of view adopted by psychology result a number of general psy- chological tendencies which we shall seek to review in the first chapter of this book. The development of opinion regarding principial questions in psychology, as exhibited in certain fundamental psycho- logical concepts, has a certain historical continuity of its own. 1 Cf. Wundt, “Uber reine und angewandtePsychologie,” Psychologische Studien, V, pp. 1 ff. INTRODUCTION 5 In this respect, too, psychology differs characteristically from the natural sciences. Theories regarding the connections of external phenomena appear comparatively early in the his- tory of civilization. The antithesis between the teleological and the mechanical views of nature, for example, is already clearly presented in the writings of Aristotle and Democritus, and the antithesis has persisted throughout the whole subse- quent history of science. Principles of a similar nature ap- pear much later in the history of psychology. The inner life of man was not only not an immediate object of theoretical investigation, but it was from the outset subjected to the in- fluence of ethical and religious ideas. While the task of nat- ural science was merely to subject recognized phenomena to scientific treatment and interpretation, psychology was first obliged to bring the phenomena with which it dealt into con- scious existence. The act of willing, for example, which ap- peared in the first place as either good or bad, had to be viewed as a pure experience, without reference, that is, to its ethical or social significance; or the features which are common to a sensation, as a cognitive process and, say, a feeling of pleasantness had to be determined, etc. It is such efforts as these that we shall seek to follow in our second chapter, which deals with the fundamental concepts of psy- chology. Finally, there have arisen in connection with a number of psychological problems, such as sense-perception, volition, etc., certain theories which cannot always be readily fitted into the framework of a systematic psychology, but which can be treated historically, since it is the same problems which persist throughout all the metamorphoses which their explanations undergo. We shall, of course, understand by the phrase “psychological theories” only such concepts and principles as are able to meet the demand which every sci- entific theory must meet, viz., that it shall connect phenom- 6 HISTORY OF PSYCHOLOGY ena with their causes in accordance with natural laws. The older doctrine of mind-stuff, for example, is not a psycholog- ical theory but a metaphysical interpretation of mental phe- nomena. The history of the most important of these psy- chological theories will be dealt with in the final chapter. Since the development of psychology is but a phase of intellectual development in general, it would doubtless be possible to identify in psychology the same general stages through which the history of intellectual culture has passed. The attempt, however, to deduce from the latter the laws for the historical development of psychology would be fruit- ful only for special tendencies or problems of psychology or else it would lose itself in unprofitable generalities. As an example of the latter we might cite the three organic laws for the development of psychology enumerated by Maurice de Wulf, 1 which, however, tell us nothing more than that psychology passes from a dogmatic through a critical stage in order to complete its development when the human spirit itself reaches its maturity. It has seemed to us a more interesting and attractive task simply to follow the move- ment of history and to separate out from the broad stream of tradition those ideas which appeared significant and which are sometimes so much in advance of their time that we feel a sense of kinship with bygone thinkers as if they belonged to our own time. 3. Modern and Ancient Elements in Psychology The principal aim of the present treatise is to trace modern psychology back to its historical antecedents. Anticipations of modern psychology are, of course, to be found at all stages of the history of the science; in fact, the order of ancient and 1 “Les lois organiques de l’histoire de la psychologie,” Archiv f. Gesch. d. Phil., X, 1897, pp. 393 ff. INTRODUCTION 7 modern is not seldom curiously reversed. Who, for example, does not find in Alhacen’s Optics, published in 1269, a mode of thinking more akin to our own than that contained in many of the speculations of the school of Schelling concerning the alleged analogies between sense qualities and the mode of appearance of physical forces? And if we go back still further we shall find a form of mental mechanics in Aristotle which, as an anticipation of modern explanatory psychology, ranks far above the Wolffian faculty psychology of the eighteenth century. It is difficult, accordingly, to assign with much confidence a date at which modern psychology may properly be said to begin. There is hardly a division point in the history of philosophy which may not also, from some point of view, be regarded as the beginning of modern psychology. If one is thinking of psychology as an exact, experimental science, developing in close relation to physiology, then modern psy- chology may be said to date from the middle of the nine- teenth century. Frequently the empirical psychology of the eighteenth century, in which individual psychology and psy- chiatry were closely connected interests, is pointed out as a mode of thinking which is related to our own. John Locke, the founder of the so-called psychology of the inner sense, is usually named as the founder of modern empirical psychol- ogy, thus placing the beginning of modern psychology near the end of the seventeenth century. Again, the significance which Descartes’ definition of consciousness assumed for psychology has been thought sufficient to make the Car- tesian system the dividing point between ancient and modern psychology. Still further back do we find empirical psy- chology explicitly contrasted with the traditional meta- physical psychology, as by Ludovicus Vives, who has him- self been called the father of modern psychology, thus placing the beginning of the science in the first half of the sixteenth 8 HISTORY OF PSYCHOLOGY century. Siebeck’s researches, finally, have detected the fruitful beginnings of empirical psychology in Scholasticism. Observations on certain striking color phenomena are utilized for illustrative purposes in the theological tractates of the followers of Eckhart, which exact psychology has been very tardy in taking into account. Although these beginnings of empirical psychology consist mainly in a departure from the Aristotelian tradition, it must not be forgotten that the Aristotelian writings contain anticipations which extend into the most modern times. Although, therefore, our task takes us back into the re- motest antiquity, the history of psychology, perhaps more than the history of any other science, falls into periods and epochs in which scattered ideas of real significance stand out in clear relief against a colorless mass of traditional learning. A proper historical appreciation of such phenomena is often made difficult by the exaggerated estimate of some single thinker, like Aristotle, for example, who is often said to have had only predecessors and imitators. Some such remark might, indeed, apply to certain ideas in the history of science, particularly in the history of psychology of which it can truly be said that they have had only anticipations and developments. 4. Literature The first attempt to write the history of psychology was made by Aristotle {Be Anima, I, 2). But it is not until the historical sense is awakened by Romanticism that the study of the history of psychology begins. The most notable work which has come down to us from this period, a book which is still instructive on many points, is F. A. Carus’s Geschichte der Psychologie, published in 1808. If we confine ourselves to the one most important modern INTRODUCTION 9 work for the discussion of any given period, the most ex- haustive work on the history of ancient psychology down to Thomas Aquinas is H. Siebeck’s Geschichte der Psychologie (1880-4), which is supplemented by a series of articles on scholastic psychology, published in Archiv fur die Geschichte der Philosophic, I— III (1888-90). No work of similar scope and value exists for the period of the Renaissance and for the metaphysical systems of the sixteenth century. In fact, there is no other period in which scientific psychology breaks up into so many scattered observations and unrelated points of view. The most complete account of the period from Leibniz to Kant is contained in Dessoir’s Geschichte der neueren deutschen Psychologie, part I (2d ed., 1902). The main problems of the history of psychology in the nineteenth century are treated, very unevenly, to be sure, by Eduard von Hartmann, in his Die moderne Psychologie, 1901 (Werke, XIII). A circumstantial account of the more modern ten- dencies of psychology is to be found in Ribot’s Psychologie anglaise contemporaine (2d ed., 1875), and Psychologie alle- mande contemporaine (2d ed., 1885). The points of view, finally, wdiich have dominated the developments of experi- mental psychology have been briefly summarized by Wundt in his article “Psychologie,” contained in the Kuno Fischer Festschrift, Die Philosophie im Beginn des 20. Jahrhunderts (2d ed., 1906). Among the works on systematic psychology Volkmann’s Lehrbuch der Psychologie (4th ed., 1894-5) contains a wealth of historical references and excursions which is worthy of admiration even to-day. With neither of these works, each of which is based upon an extensive literature in the form of monographs and special investigations, does the present book wish to enter into com- petition. It rather presupposes them, as it does the study of the sources, and it should be supplemented by references to them. Siebeck’s and Dessoir’s books, particularly, are 10 HISTORY OF PSYCHOLOGY utilized extensively in the treatment of ancient psychology and the psychology of the Enlightenment, respectively. But the writer does hope that the treatment of psychology in its historical development will exhibit the problems of contem- porary psychology in their genesis and will thus prepare the way for their independent study and treatment. At a time when psychology is taking her place as an independent empirical science among her sister sciences such a treatment will, perhaps, help to obviate certain misunderstandings such as are illustrated in profusion in the attempt of a brilliant contemporary writer to prove that psychology is quite with- out prospects. In thus tracing the development of psy- chological reflection, certain border problems occupy atten- tion perhaps somewhat more than their importance may seem to warrant at a time when psychology is taking her place among the other sciences as a special empirical science. In the history of psychology, however, the border lines be- tween science and hypothesis have always been obscure. It is the hypothetical element in psychology, in fact, which has invested psychological problems with peculiar interest and vitality. One is reminded here of the statement of Poincare that the growth of a science occurs along its borders. Translators’ Note on English Literature The reader may also be referred to the following works on the history of psychology which have appeared in English either as original works or as translations: Baldwin, J. M., History of Psychology, New York and London, 1913. Brett, G. S., A History of Psychology, London, 1912. Dessoir, M., Outlines of the History of Psychology, tr. of Abriss einer Geschichte der Psychologie, by Donald Fisher, New York, 1912. INTRODUCTION 11 Ribot, Th., English Psychology, tr. of the work cited above, by J. M. Baldwin, New York, 1897. Ribot, Th., German Psychology of To-Day, tr. of the work cited above, by J. M. Baldwin, New York, 1899. PART 1 GENERAL TENDENCIES OF PSYCHOLOGY I. METAPHYSICAL PSYCHOLOGY CHAPTER I DUALISM IN PSYCHOLOGY i. Relation of Metaphysical and Empirical Tendencies Although psychical phenomena are of all data the most accessible, the history of psychology bears witness to the extreme difficulty of gaining the proper point of view for the study of the phenomena in question. Psychology, indeed, appears surprisingly early as one among the other sciences, but for centuries psychology does little more than reflect the presuppositions and conclusions of philosophy. When the points of view of a metaphysical world view are trans- ferred to the realm of conscious phenomena, the latter appear as manifestations or modes of activity of a soul, an entity usually thought of as substantial. The particular phenomena of consciousness are deduced from the concep- tual definition of the soul. Side by side with metaphysi- cal psychology appears empirical psychology which makes psychical phenomena objects of introspection, and seeks to exhibit their scientific connection. The metaphysical and the empirical tendencies are by no means mutually ex- clusive. Empirical materials are to some extent utilized in every type of metaphysical psychology, and empirical psy- chology, on the other hand, gives rise to problems which 12 DUALISM IN PSYCHOLOGY 13 properly belong to metaphysics. In this respect psychology does not differ from the rest of the factual sciences. And if metaphysical problems arise more inevitably in psychology than in some of the other sciences, it is doubtless due to the close affinity between the subjective mode of viewing the contents of consciousness and the reflection upon the move- ments of the inner life which so naturally carries one forward to a metaphysical view of existence. The various tendencies within metaphysical psychology exhibit a close resemblance in the manner in which psychical phenomena are deduced from the concept of the soul, the difference appearing in the definition of the soul itself. The empirical tendencies start with the same method, that of introspection; they differ from each other mainly in the principles e~ ployed in the interpretation of the data which introspection reveals . 1 The oldest forms of metaphysical psychology were domi- nated by categories developed within the domain of natural science, from which they were transferred to the realm of the inner life. The soul, accordingly, appears as an entity, a substance, corresponding to substances and things in the external world. There occurs thus a complete reversal of the more familiar anthropomorphic modes of thinking: psychical facts, in order that they may be thought real at all, are brought under concepts originally derived from the domain of external nature. The contrasts between spirit and matter familiar in meta- physical systems thus reappear in psychology in the specula- tions concerning the nature of the soul. The most natural con- ception here is dualism, which opposes material substance and soul substance. Attempts to transcend this antithesis lead 1 These and a number of subsequent distinctions are drawn from Wundt’s Grundriss der Psychologies 1909. [English tr. by C. H. Judd, Outlines of Psychology, 2d ed., L'ipzig, 1902. Trs.] 14 HISTORY OF PSYCHOLOGY to spiritualistic psychology, in which physical processes are held to be essentially identical with psychical processes, and materialistic psychology, in which psychical processes are held to be merely a mode or a manifestation of matter. 2. Dualistic Psychology Dualism results from the introduction of prescientific ideas into the whole of a world view in which the phenomena of reality have been subjected to little or no interpretation. For primitive thought, man, like everything else in the world, is a composite of body and soul. As knowledge in- creases, many objects are bereft of soul life, so that event- ually only living beings remain endowed with psychical qualities. These conceptions of primitive peoples form the subject-matter of folk psychology. They are of interest to the history of psychology, since they have been made the objects of conscious reflection and have been raised to the dignity of psychological theories. From the earliest repre- sentatives of Oriental philosophy to the time of Plato we find a primitive dualism which teaches that the soul leads only a shadowy existence after its separation from the body. The first attempt to give a connected account of mental phenomena within the framework of a metaphysical world view is made by Heraclitus of Ephesus. The system of Heraclitus, like that of his predecessors, is monistic in the primitive sense of the term. All things, including the soul, originate from fire, the soul appearing at that stage of the evolution of the universal element where the latter breaks up into earth and fiery vapor. In the human organism the body represents the earthy, the soul the fiery element. Through the breath it partakes of the warm air and thus of the same rationality as fire is supposed to possess. Its origination and destruction are merely phases of the general DUALISM IN PSYCHOLOGY 15 rhythmic movement of existence: “It is death to souls to become water, and death to water to become earth. But water comes from earth; and from water, soul.” The ex- perienced difference between body and soul Heraclitus ex- plains by the hypothesis that they represent two stages in the development of fire. The knowledge of the soul accord- ingly presupposes a knowledge of reality as a whole. Like the universe, it is unfathomable, as the well-known saying testifies: “You will not find the boundaries of soul by trav- elling in any direction.” 1 It is not until we come to Empedocles of Agrigentum that Ionic hylozoism becomes consistently dualistic. It is true that Empedocles reduces all becoming to relationships of matter and force. Matter is composed of four elements, while force manifests itself in the interplay of attraction and repulsion, figuratively called love and hate. The soul, how- ever, is not affected by these physical theories. The hypoth- eses of the philosophy of nature that the soul, like everything else, consists of the various elements combined in the proper proportions become mingled with religious ideas according to which the individual soul is merely a part of the world soul. The elements themselves are now transformed into divinities; the soul is capable of an existence separate from matter, and the doctrine of metempsychosis clearly indicates contact with Pythagorean ideas. Pythagorean psychology, from all we are able to ascertain concerning the matter, was also dualistic in character. The saying that the soul is a harmony, or possesses harmony, was already within the Pythagorean school a statement of equivocal significance. It is beyond question, however, that the dualism of body and soul was for the Pythagoreans merely a repetition of the familiar antithesis between the unlimited and the limited, between matter and force. 1 [Burnet, Early Greek Philosophy, p. 138. Trs.] 16 HISTORY OF PSYCHOLOGY A new form of dualism, in which the priority of spirit over matter first received recognition, is represented by Anaxag- oras. To the indistinguishable mixture of all things, which represents the material world, is opposed a homogeneous and independent principle which furnishes the condition of mo- tion. This principle of movement is at the same time a principle of order and intelligence (vou?). In the descrip- tion of the vow a tendency toward pure spiritualism makes itself felt. It is unmixed, unitary, and free from suffering. It is self-governing; it possesses all knowledge and very great power. On the other hand, we find the idea persisting in Anaxagoras that the spirit is but a part or a fragment of matter. He calls it “ the finest and purest of all things,” and the soul becomes again a part of that spiritual essence which pervades things, “now increasing, now diminishing.” Although theoretical speculation often advanced to the doc- trine of the purely spiritual existence of the soul, it did not develop, unaided, the conception which has been a mainstay of dualism, the conception of immortality. Neither could the belief in immortality develop from the soul cult of Greek popular religion. It rather originates in mysticism, which j had its bands of votaries among the Greeks and existed side by side with the popular religion, little heeded by the latter. In the Orphic and Eleusinian mysteries are heard the echoes of the worldly wisdom of ancient India according to which the body is the sepulchre of the soul (acofia arj/xa ijrvxvs)- The idea of immortality found fruitful soil in the cult of Dionysos in which the experience of ecstasy furnished materials sufficiently striking for spiritualistic hypotheses. The convulsive movements and visions in the moment of divine madness must have suggested a realm quite removed from the ordinary realities of every-day life. The belief in the separate existence of the soul which the experiences of dreams and swoons made natural was thus confirmed by the DUALISM IN PSYCHOLOGY 17 experiences during ecstasy. It was an easy step from this point to the doctrine of the dual existence of body and soul. The descent from the heights of emotional ecstasy, to which the soul had been raised upon its temporary release from the body, to the realities of the bodily life came to be felt as a passage from one world into another . 1 The inclusion of these conceptions within a theoretical world view brought psychological dualism to its highest point of development, a point reached in the philosophy of Plato. In Plato’s theory of ideas the soul is assigned a sort of intermediate position between the world of ideas and the world of matter, since the soul knows ideas, but is itself bound to the body. The fundamental contradiction between experience and the conceptual world, which runs throughout the entire Platonic system, is nowhere revealed more strikingly than in the relation between body and soul. They do not constitute an organic unity; the body rather appears as an obstacle hindering the soul in the attainment of knowledge and of its true life. The complete contrast between the body and the soul is, indeed, made the condition of the latter’s immortality. This pronounced dualism reap- pears in the empirical constitution of the soul, which con- tains two elements, a natural and a supranatural. The con- trast between the spiritual and the natural assumes a more striking form in Plato than in Anaxagoras. Although the connection between body and soul becomes thus an insoluble riddle, the soul becomes thereby an object of supreme inter- est for speculation. While the knowledge of the empirical world is for Heraclitus a precondition of the knowledge of the soul, as we have seen, the relation here is completely reversed : the knowledge of the soul forms the only avenue to the knowledge of the world. Plato thus drew the pregnant consequences involved in the positions of the Sophists and 1 Cf. Rhode, Psyche, II, 1898, pp. 32 ff. 18 HISTORY OF PSYCHOLOGY Socrates, and the existence of psychology as an independent science is demanded, even if not actually assured. It was impossible to carry dualism to a higher point of develop- ment than it had attained in Plato. It is not until the be- ginning of the modern era in philosophical speculation that we find a dualism equally consistent and thoroughgoing, though it is now based upon a different conceptual formulation. A number of dualistic features appear also in the psy- chology of Aristotle, whose metaphysical presuppositions lead him to make the distinction between the active and the pas- sive reason. The active reason is of divine lineage; separated from the organic development of human mental life, it enters this life from without ( dvpadev ). Such an obvious contra- diction Aristotle, master that he was of the art of conceptual manipulation, could not allow to remain unrelieved. His metaphysical theory that every movement presupposed three conditions, something moved, something at once mover and moved, and, finally, an unmoved mover, suggested the solu- tion: reason in the human soul discharges the same function as the divine being in the universe as a whole, that, namely, of an unmoved mover. Like the divine being, it represents the capstone of organic evolution. A source of dualistic ideas similar to that of the Dionysian cults is to be found in the Hebrew representations of the soul. The fusion of Hebrew and Greek conceptions in Alexandrian- Judaic psychology is illustrated in the system of Philo, an older contemporary of Jesus, according to whom the human body is composed of earthy elements, while the soul, which traces its lineage to the divine 7 rvev/xa, is composed of ether. Platonic dualism is here seen to approach again the Orphic- Pythagorean conceptions, thus giving way to a supranatu- ralistic theory of soul life which for a long period dominates philosophical speculation. It is here, too, that a differentiation is effected between two DUALISM IN PSYCHOLOGY 19 factors which had been united in the traditional notion of the soul, a physiological factor, vital force, and a psycho- logical one, consciousness. The distinction indeed already existed in germ in Aristotle. Stoicism, too, had prepared the way for the separation of these elements by their dis- tinction between the r/yefiovucov and the 7 rvev/ia, thus creat- ing, by a partial interpretation of the Aristotelian “quinta essentia,” the conception of “animal spirits,” spiritus ani- mates, a conception destined to a long-lived existence in the history of psychophysical speculation. This higher part of the soul, which had hitherto been regarded as merely a general principle of rationality, is now designated as a principle of individuality as well. The threefold division of the personality into spirit, soul, and body dominates anthropology from this time on. While this triadic theory obviously represents an attempt to connect psychology with religious ideas and interests, it also suggests misgivings on the part of those who held the theory that the complex variety of psychical phenomena may, after all, not be capa- ble of derivation from a single unitary principle. An ex- haustive exposition and proof of the triadic theory is under- taken by Origen (185-254), who ascribes to the soul the powers of movement, representation, and desire, the spirit being endowed with the power of judgment. 1 The exposition contained in the metaphysical system of Plotinus is of a very similar character. Separate indepen- dent and substantial souls owe their existence to the world soul. The incarnation of the soul within the body is to be explained by the fall of the soul from a previous state of blessedness. The relation of the soul to the body is com- pared with that between light and air. It is said to be “everywhere present without surrendering its identity, pen- etrating everything without mixing with it.” 1 De princ., Ill, 1-5. 20 HISTORY OF PSYCHOLOGY The influence upon psychology of the religious mysticism of the Neo-Platonists after Plotinus becomes more pro- nounced as time goes on. The Neo-Platonic definition of the soul given by Porphyry, ovaia apeye0r]<; avXos afydapTOs iv fc or) 7 rap eavTrj ? e^ovarj to %rjv ice/CTT) pevrj to eivai } is widely followed by the Greek Church Fathers. Prominent among the amalgamations of Christian and Neo-Platonic ideas are the teachings, based upon the system of Plato, of Gregory ofNyssa (331-394). He considers the soul as an incorporeal, independent substance which permeates the body. The lat- ter phrase, however, is not to be taken in a spatial sense; the relation between soul and body is much like that between light and air. More convincing proofs of the incorporeal nature of the soul are offered by Augustine (354-430). The idea that the knowledge of a thing implies an ontological affinity between the knower and the thing known, and that, consequently, that which knows the incorporeal must itself be incorporeal, is reminiscent of Plato. More important is the purely psy- chological argument that the soul, since it is the experiencing subject, cannot be itself an object of observation and cannot, therefore, have material properties. The soul has an imme- diate knowledge of itself in self-consciousness. The problem of the relation between soul and body Augustine seeks to make intelligible in a manner characteristic of his time. The reigning dogma of soul substance prevents him from advancing to a monistic position and leads him to assert that the combination in man of body and soul results in a third substance, the exact nature of the relation between these substances, however, remaining unfathomable. A clear expression of the tendencies of later Patristic psy- chology is found in the teachings of Nemesius, bishop of Emesa in Phoenicia, who wrote between 400 and 450. Tak- ing his stand against both materialism and the Aristotelian DUALISM IN PSYCHOLOGY 21 doctrine of the soul as the entelechy of the body, he defends an outspoken dualism of body and soul, contenting himself with the definition of the latter as an incorporeal, inde- pendently existing substance. The psychology of Scholasticism, too, is largely dominated by dualistic conceptions. The early Scholastics, Alcuin, Isaac of Stella, and Hugo of Saint Victor, base their ideas upon the Augustinian-Platonic system. With the rehabilitation of Aristotelianism in the thirteenth century this develop- ment is for a time interrupted, but the fundamental idea of spiritualism soon succumbs again to dualism, which received powerful support from its affiliation with current religious convictions. The Arabian philosophers also assisted the cause of dualism by making the necessary reinterpretations of the distinction between the active and the passive reason. The authority of Aristotle served also to protect partly the pneuma doctrine which, originally growing out of hylozoistic ideas, was now employed to explain the connection between soul and body. Pneuma became a sort of intermediate agent, so that the main outlines of the triadic philosophy, with its division of spirit, soul, and body, were again restored. A naturalistic interpretation of Aristotelian doctrines oc- casionally bordering upon pantheism was given by Averroes (1126-98). 1 The soul is distinguished both from the body and from the impersonal intellect. The aim of intellectual knowledge as it develops is the comprehension by the uni- versal intellect of its own activity and life within the indi- vidual, a process which Averroes describes as the attainment by the intellect of abstract ideas. 2 And since forms emerge from matter of necessity, in virtue of the principle of move- ment inherent in matter from eternity, the development of 1 Cf. Siebeck, Archiv f. Gesch. d. Phil., II, pp. 516 ff. 2 “ Ascendit ille intellectus in actu ad assimilationem rerum abstrac- tarum et intelleget suum esse, quod est actu intellectus.” De an. beat., 66 A. 22 HISTORY OF PSYCHOLOGY the spiritual principle is a process which is both natural and necessary. It is true that Thomas Aquinas (1224-75), standing at the very summit of Scholasticism, turned away from Platonic dualism and accepted the Aristotelian conception of the soul. The dogma of the church, however, demanded an adapta- tion of the Aristotelian distinctions so as to bring them into harmony with the reigning system of theoSgical dualism. He accordingly made the distinction between subsistent and inherent forms and attributed to the former an existence in- dependent of matter. The comment often made upon the philosophy of this period, namely, that it is no more and no less scientific than the literary sources upon which it drew, applies, on the whole, to psychology as well, whose affiliation with philosophy was at this period constant and intimate. In the period immediately preceding modern philosophy dualistic theories underwent few modifications. This ap- plies, for instance, to the Marburg school, known to us through the Psychologia of Rudolf Gockel, published in 1590. 1 Modern dualism originates with Descartes (1596- 1650) where it is based upon new conceptual presuppositions. Descartes did not, indeed, succeed in liberating himself com- pletely from the scholastic tradition. Still, his thinking was dominated by the new scientific spirit of the time, with the result that the distinction between matter and spirit, which had hitherto been regarded as merely one of degree, com- pleted itself in his philosophy in the entire separation of the two spheres in question. Descartes thus for the first time assigned to the physical and the mental sciences their dis- tinct subject-matter: to the former extended substance, to the latter conscious substance. There is probably no other distinction in the history of 1 Casmann defines man as “ genuinaj naturae mundanse: spiritualis et corporea in unum hyphistamenon unite participes essentia;.” DUALISM IN PSYCHOLOGY 23 metaphysical psychology which has been as momentous as this. The conceptions and categories of the older systems of philosophy are often so ambiguous in character that it is impossible to say whether they are physical or psychologi- cal. They seem to fall somewhere between. Even where the antithesis between the two realms is made explicit, as in Plato, it tends to pass over into the antithesis between the good and the bad or between the true and the false. The transformation which occurred is well-nigh impossible of vital apprehension to-day, for the Cartesian distinction still coincides with the concepts in accordance with which naive thought interprets the whole of our experience. With the Cartesian substitution of a pure dualism of substances for the Platonic dualism of values the problem of the relation of mind and body was raised into greater prominence than ever before. The attempts to solve this problem were of first- rate influence in carrying psychology beyond the dualistic hypothesis. To be sure, dualistic ideas come into promi- nence again with the return to the great metaphysical sys- tems of the seventeenth century, especially in the popular philosophy of the Enlightenment. Indeed, the Cartesian dualism became the generally accepted view-point of popular thought. As a metaphysical tendency, however, it hence- forth assumes a subordinate rank. And although we find writers even in the nineteenth century who espouse dualism, like Krause, for example , 1 they do not do so without exhib- iting monistic tendencies. With the exception of the innovation of Descartes which influenced every subsequent psychological tendency , 2 the development of dualism was fairly consistent and uniform. In this respect it resembles the earlier forms of empirical psychology, to be described later, especially faculty psy- 1 Vorlesungen uber die psychische Anthropologie, 1836. 2 Cf. below, Chapter VI, 1 ( b ). 24 HISTORY OF PSYCHOLOGY chology. The reason for this lies in the fact that dualism never undertakes any genuine interpretation of the phenom- ena of experience. It is only with the progress of sophisti- cation that the wealth of contrasts shown by monistic ten- dencies becomes possible. CHAPTER II MONISM IN PSYCHOLOGY Monism in psychology can either grow out of the problems raised by dualism or it can from the outset treat psychical and bodily phenomena as equivalent. In the former case, the point of departure is the problem of the mutual relation of body and mind; in the latter, the common characteristics of bodily and mental phenomena become the starting-point. Speaking generally, the effort to identify the soul, taken as an independent reality, with the body, leads to the primacy of the former and thus to spiritualistic psychology. On the other hand, the identification of bodily and psychical proc- esses tends to make the physical world appear as the real world, and the result is materialistic psychology. It hap- pens, accordingly, that in the history of psychology spiritu- alistic tendencies follow in the wake of a pronounced du- alism, while materialistic psychology grows out of natural science when carried on independently of metaphysical pre- suppositions and influences. But the relation is sometimes reversed, with the result that one finds very diverse tenden- cies combined in a given form of spiritualistic or material- istic psychology. Between these two types stands pure monism, such as one finds in Spinoza, for example, which co-ordinates completely the physical and the psychical aspects of reality. Since this theory, however, fails to take account of the empirical con- nections existing among the contents of consciousness, it can hardly be said to constitute a separate branch of meta- physical psychology, although it bears close relations to ef- 25 26 HISTORY OF PSYCHOLOGY forts to rid a given system of empirical psychology of con- tradictions and thus to bring it to a definitive conclusion. Within the science of psychology itself the principle of so- called psychophysical parallelism has been reduced to a heuristic principle, a process which has been repeated in the case of metaphysical principles of a number of other sciences, the principle of finalism, for example, in biology. i . Spiritualism Spiritualism in psychology is the result of the gradual development of the concept of spirit and of the sharpening of the contrast between spirit and matter. A number of spiritualistic features are found as early in the history of psychology as Anaxagoras, who describes spirit as something simple and unmixed; but his definitions are not free from materialistic implications. 1 It is not until Aristotle (384- 322), the thinker who might be said to have originated psychology as an independent science with definitely fixed boundaries, that the magic word expressing the really inex- pressible nature of the soul was spoken. The soul is to the body what form is to matter; it is that which makes of the body a living being, and which through its activity completes the body, by leading it to its true goal. This is the meaning of that noteworthy definition of the soul as the entelechy of the living body : eartv ovv ivr eXe^eia rj rrpcorrj era) paros vcriKov £ corjv eyot>TO? Bvvap,ei. In this conception of the soul are contained the initial suggestions which psychology has not availed itself of until the most recent times. In Aristotle’s psychology the soul is no longer a substance, but an activity, a formative principle. The most important conception of spiritualistic psychology comes here to its full- est expression, although Aristotle, influenced by his meta- 1 Cf. above, p. 16. MONISM IN PSYCHOLOGY 27 physics, again lapses into dualism. 1 In spite of repeated at- tempts on the part of Neo-Platonism to construct a monistic psychology, spiritualism remains a subordinate type for a considerable period. It is revived again in the metaphysical systems of modern philosophy, reaching its highest develop- ment in Leibniz (1646-1716), the Aristotle, as he has been called, of modern times. The psychology of Leibniz is based upon the doctrine of monads, a wholly metaphysical conception. Inasmuch as the soul is the only part of reality which we immediately know, we must interpret the rest of reality in analogy with it. All reality is, therefore, psychical in character. It is composed of monads of varying degrees of development ar- ranged in a hierarchy whose order is determined by the particular grade of development reached by the monads composing it. On the lowest plane are found simple mon- ads, whose psychical condition resembles our own in a state of drowsiness or swoon. Animal souls are endowed with memory. The human soul, finally, participates in the high- est forms of experience through its knowledge of necessary truths. Since all the grades of consciousness are repre- sented in the monad constituting the human soul, the meta- physical conception in question, although confining itself to cognitive experiences, was not without significance for the interpretation of the empirical data of consciousness. 2 The purest form of spiritualism ever achieved, that of Berkeley (1685-1753), arose out of different antecedents. The starting-point of Berkeley’s system, it is true, was the empirical psychology of Locke, since he characterized all experiences as forms of self-observation. But his interpre- tation of sense-perception as the lowest form of self -observa- tion already carries him beyond the bounds of experience. 1 Cf. above, p. 18. s Cf. below, Chapter VI, 2 (a). 28 HISTORY OF PSYCHOLOGY Once thoroughly launched upon metaphysics, Berkeley finds nothing but souls and their experiences. The soul is a sim- ple, indivisible, active being which, in its capacity to per- ceive ideas, is called intelligence; in its capacity to produce them, will. The peculiarity of the subject of inner experi- ence is suggested by the observation that we can form only a concept, not an idea, of spirit; nevertheless, the definition of spirit here proposed carries us far beyond the bounds of science into metaphysics. The spiritualistic psychology which nourished itself on the Leibnizian ideas tended always to lapse into vulgar dualism. After Kant had dealt the death-blow to this species of psy- chologizing, as well as to the more traditional type of ration- alism, psychology passed under the sway of the Romantic philosophy. A related form of spiritualism is found in France after the Revolution. Cabanis (1757-1808) had, in- deed, sought to explain the relations between physiological and psychological processes in his principal work, Les rap- ports du physique et du moral de I’homme (1798-9 and, separately, 1802), but he assumed with Leibniz a number of subordinate minds in addition to the central mind, even- tually adopting a form of pantheism not unlike that of an- cient Stoicism. A complete contrast to sensualism of the type found in Condillac is encountered in Maine de Biran (1766-1824), who has done much for the revival of psychology in France. In his Essai sur les fondements de la Psychologie he opposes equally the point of view of the metaphysicians who treat the soul as an absolute being and that of pure empiricists who recognize in the mental life only sensations and connec- tions among sensations. Reflection on our inner life forces us to recognize conation or wilful effort as the primary fact of consciousness. Will and resistance are inseparable ex- periences: it is through resistance that the self becomes MONISM IN PSYCHOLOGY 29 aware that it is limited. Other deductions of Maine de Biran remind one of the interpretations of consciousness in German Romanticism. A characteristic doctrine is that of inner space. This is the immediate seat of the ego and is formed by the various points of resistance which the will encounters in the various organs. The Leibnizian tradition is continued by Herbart (1776— 1831), who himself acknowledged Leibniz as his precursor. Herbart, too, is not exempt from the influence of the dia- lectic of Romanticism in so far as the problem of psychology arises only as a result of the contradictions contained within the concept of spirit. In the fact of self-consciousness is contained, according to Herbart, the identity of being and knowledge, of the subject and object of consciousness, without being differentiated within it, however, by thought. Thus psychology confronts a metaphysical problem at the very outset and it emerges from its attempts to solve this problem as a mechanics of ideas. On account of the contra- dictions among the empirical concepts to which experience gives rise, the latter does not even furnish us with phenomena from which the nature of reality might be inferred. It gives us nothing but semblance, and this semblance it is the busi- ness of metaphysics to dissipate. With this object in mind, Herbart resorts to the Leibnizian monadology. He defines even more sharply the concept of the individual, simple being of “the real.” Out of the disturbances and the ten- dencies to self-preservation or persistence of these reals he deduced both the phenomena of the outer world and the processes of consciousness. The latter consist entirely in the movements of ideas. The whole of reality is thus dis- solved, as if by an act of force, into reals. The physical and psychical represent merely different stages in the competi- tive action, the disturbance and self-preservation, of simple elements. 30 HISTORY OF PSYCHOLOGY Aside from this main line of the development of spiritual- ism which has persisted in its Herbartian form up to very- recent times, other spiritualistic motives have made them- selves felt in the nineteenth century, especially in connection with the school of Schelling. The Aristotelian definition of the soul reappears in the Vorlesungen iiber Psychologie (1831) by C. G. Carus, who again defines it as the principle of life. Fantastic analogies between body and soul, between organs and their functions, are met with' in a number of psy- chologists representing similar tendencies, Schubert, Fischer, Burdach, and Heinroth, whose names have now passed into oblivion. This form of spiritualism received its most ex- haustive treatment at the hands of J. H. Fichte (1797-1879), who combined a strong theological tendency with the most fanciful psychological hypotheses. Much more congenial is the mature form of spiritualism which serves as the background of the empirical psychology of one of the most important psychologists of the nineteenth century, Hermann Lotze (1817-81), the successor of Her- bart at the University of Gottingen. Lotze’s thought is firmly based upon natural science, and he recognizes fully the dependence of mental states upon bodily condition. Never- theless, the ultimate ground of reality is for him spiritual. “Thus we are led back,” he writes, “to a psychophysical mechanism within which all interactions occur among homo- geneous elements. This does not mean that we reduce mind to terms of matter, as is done by materialism, but rather that we interpret matter in terms of mind, or of some substance essentially akin to mind.” 1 Within the movement of spiritualism itself several sharply contrasted tendencies have lately made themselves felt. In contradiction to the fundamental metaphysical principle that the soul is a spiritual substance and the empirical principle 1 Medicinische Psychologie, 1852, p. 80. MONISM IN PSYCHOLOGY 31 that the intellectual processes furnish the foundation for all other mental processes, the claims are advanced, first, that the immediately experienced actualities of the mental life are themselves the ultimate reality of that life, and, second, that the phenomena of volition represent the fundamental traits of mental life as a whole. Thus arises the distinction be- tween substantialism and actualism, on the one hand, and between intellectualism and voluntarism, on the other, these constituting the metaphysical border problems of contem- porary psychology. Anticipated by Hume and Kant, who had subjected the notion of spiritual substance to a vigorous criticism, actualism is represented at the present day mainly by Wundt and Paulsen, who also champion a pronounced voluntarism as against various forms of intellectualism. The controversy between substantialism and actualism turned mainly upon the metaphysical question whether the relation between the substantial beare? of qualities and the qualities or phenomena themselves was thinkable. As was to be expected, the influence of these considerations upon empirical psychology has not been very great, as can be seen by com- paring the theories, say, of Lipps and Wundt, the former of whom showed on the whole a tendency toward substantial- ism. Of more empirical significance is the controversy between intellectualism and voluntarism. The latter has antece- dents in the history of psychology in various theories of the will which go back to Duns Scotus, or to the end of the twelfth century . 1 A distinction, must, of course, be made between metaphysical voluntarism, such as we associate with the name of Schopenhauer, and psychological voluntarism, which regards the empirical process of volition, with its affective, sensational, and ideational constituents, as the type of consciousness in general. It is just in the composite 1 Cf. Chapter XII, 2, below. 32 HISTORY OF PSYCHOLOGY character of the volitional process that its typical signifi- cance lies . 1 This principle, however, which was originally meant to be merely a methodological principle, tends very readily to become transformed into the dogma of the meta- physical priority of volition. If we review from this point the development of spiritual- istic psychology we shall recognize the tendency to shift the problem of spiritualism to the realm of the border problems of psychology. The various tendencies of spiritualism, in so far as they have relevance for psychology, meanwhile exhibit a noticeable similarity for a considerable period, since, while extending the boundaries of the psychical, they do not re- sort to heterogeneous principles of explanation, as material- ism so often does. 2. Materialism in Psychology Materialistic psychology divides into three main forms according to the relation asserted to exist between mental and physical processes. In the most naive form of this doc- trine the soul is treated as a special kind of substance which penetrates the body, or else it is outrightly identified with some part of the body, usually the brain. Since this form resolves the soul into atoms similar to the atoms of physics, it may be called atomistic materialism. The growing knowl- edge of brain processes combined with epistemological con- siderations rendered atomistic materialism unsatisfactory and led to the interpretation of mental processes as the effect of brain processes. Thus arose mechanistic materialism, a form which developed concomitantly with the mechanistic conception of nature. The third most general form is psy- chophysical materialism, according to which mental processes are functions of specific bodily processes. While atomistic 1 Cf. Wundt, Grundriss der Psychologies § 2, 10a. MONISM IN PSYCHOLOGY 33 materialism shows affiliations with substantialism in psychol- ogy, psychophysical materialism resembles actualism, since the soul here consists simply in the combination of elemen- tary psychical processes, while mechanistic materialism seems again to represent an intermediate conception. The three forms enumerated also represent roughly the historical se- quence which obtains among them. In any event, the ear- liest form of materialism to appear in the history of psy- chology is atomistic materialism. (a) Atomistic Materialism 1 The antitheses of spiritualistic and materialistic meta- physics developed out of the Jiylozoism of the ancient Io- nians, in which the concepts of soul and body were still undif- ferentiated. The first sketch of materialistic metaphysics was drawn in outline, and with bold strokes, by Democritus. The atomistic materialism of Democritus dispenses entirely with a spiritual ground of becoming. The soul is composed of a particular group of atoms, of tenuous structure, smooth and round, like those of fire. These atoms are the most mobile of all, they penetrate the entire body and impart to it the principle of life. The life of the soul depends upon the breath, i. e., upon the unrestricted supply of soul atoms. The reason the soul is invisible, Democritus quite consis- tently adds, is that the atoms composing it are too small to be seen. From these general presuppositions Democritus deduces, with admirable attention to logical sequence, the various empirical phenomena of mental life. Although the system of Diogenes of Apollonia does not correspond to the atomism of Democritus in detail, it is, 1 For the material which follows the writer is in part indebted to F. A. Lange’s Geschichte des Materialismus, which is still the most in- structive treatment of the problems of materialistic psychology that we have. [English translation by E. C. Thomas, London, 1878-81. Trs.] 34 HISTORY OF PSYCHOLOGY nevertheless, materialistic in character. The eternal and unlimited element is air, through the condensation and rare- faction of which originate cold and warmth, the dry and the moist. The soul itself is only a special form of air. A decided tendency toward materialism manifests itself in vari- ous branches of the Peripatetic school. As early as Dicae- archus of Messene we find a repetition of the old formula that the soul is a harmony, i. e., a proper proportion of the four elements composing the body. A thoroughgoing mate- rialistic psychology was developed within the Peripatetic school by Strato, the physicist, who asserted that all mental processes were modes of motion. Ignoring the subtle con- ceptual discriminations of his master, he adopted the prin- ciple of pneuma, already domesticated in the medical psy- chology of his day, as a special principle of explanation. Although pneuma was described as warm air, which pene- trates the body in respiration, the close relation of air to mental life could not be lost sight of so long as the principle of pneuma served as a connecting link between soul and body. The conception of pneuma played a leading role in the psychology of the Stoics. The less, however, they felt it as a difficulty that the fiery vapor of which pneuma was composed could be at once mental and material, the more they departed from the fundamental ideas underlying the atomism of Democritus. The sublime materialism of EpicUrus (341-270 B. C.) rep- resents the highest development to which atomistic material- ism attained. According to him, too, the soul consists of round and smooth atoms whose substance, however, is more tenuous than that of the odor of a flower or of ointment. The soul represents the union of four elements, fire, air, a vaporous substance, and a fourth unnamed element, the most tenuous and mobile of all. These physical distinctions are paralleled by certain psychological distinctions in accor- MONISM IN PSYCHOLOGY 35 dance with which spirit emerges in an analogous manner from among the other parts of the soul. So long as it remains in- tact other parts of the soul substance can perish without jeopardy to life. The materialism of Epicurus and the Stoics passed over into the psychological systems of Roman writers. The pneuma doctrine exhibited a peculiar vitality in this process, surviving up to the period of Patristic philosophy, where we meet with it quite frequently. Tertullian (160-222), from whose unmeasured polemic against Greek philosophy the work De Anima originated, adopted the materialism of Sto- icism in its crassest form. The soul is literally the breath of God ( flatus dei '); it has the same form as the body and is composed of a bright, vapory substance of great tenuity. Pneuma is no longer a special kind of substance, different from the soul: it is the soul itself, which emanates from the paternal seed at the time of birth. It has organs which it uses in thought, in dreams, and after death. It is even visi- ble to the eye of one in a state of ecstatic excitement. The same combination of religious dogmatism and extreme mate- rialism is found in Arnobius of Sicca, who finds no difficulty in uniting the ideas of the corporeality of the soul and its immortality. The materialism of Tertullian, sanctioned, as it was, by authoritative belief, survives in a number of Church Fathers in the self-contradictory definition of the soul given by Methodius of Tyre as a spiritually discernible body {aw/ia voepov ), and as late as 350 A. D. Hilary of Poitiers unhesitatingly taught the doctrine of the soul’s corporeality. Materialism disappears in the Scholastic phi- losophy, only to be revived in the seventeenth century un- der the influence of natural science and of a sensualistic theory of knowledge. The physician David Sennert (1572- 1637), who rehabilitated physical atomism in Germany, thought it possible that the soul could exist in the atoms 36 HISTORY OF PSYCHOLOGY composing living bodies, and held that seeds were atoms endowed with latent consciousness. It is upon a similar idea of animated atoms that Fortuninus Licetus (1577-1657) is said to have based his theory of spontaneous generation. The tendency of atomistic materialism, however, was to pass over into one of the other types already mentioned: mechanistic materialism or psychophysical materialism. (6) Mechanistic Materialism The philosophy of the Renaissance broke with the tradi- tion of Scholasticism without developing any marked ten- dency toward materialism. The nearest approach to mate- rialism among the leading thinkers in the early period of modern philosophy is perhaps made by Bacon. Bacon’s psychological views were extensively influenced by the con- ception of animal spirits ( spiritus aniviales), the presence or absence of which distinguishes, according to him, living from inanimate bodies. Bacon goes so far as to surmise that sensation itself consists in nothing but the movement of animal spirits. The doctrine of animal spirits is the com- mon element among many otherwise diverging tendencies in the psychology of this period. Descartes, too, utilized the hypothesis for the explanation of the manner in which external impressions can affect the soul. His belief was that animal spirits existed in the shape of highly mobile blood particles which, after being thinned by the warmth of the heart, flow to the brain in order there to form the mediating link between brain impressions and the pineal gland. 1 The real founders of modern materialism are Gassendi and Hobbes. It is the lasting merit of Gassendi (1592- 1655) that he revived the most finished system of material- ism of antiquity, that of Epicurus. Preoccupied as he was, 1 Les passions de V&me, I, 10. MONISM IN PSYCHOLOGY 37 however, with the external world, he purposely abandoned the problems of psychology with the confession that it was impossible to explain how sensation can arise out of me- chanical antecedents. 1 The hypothesis that germ particles endowed with the principle of life have existed from eter- nity seems to him to offer a way of escape from the diffi- culty. While he attributes sensation to the material soul, which is composed of atoms, he reserves thought for the rational, immaterial soul, which is created separately for each individual by the Creator. Thus Gassendi abandons that consistency of form which made the system of Democ- ritus so admirable a theoretic structure. Modern mechanistic materialism was founded by Hobbes (1588-1671), who took up the very problem which Gassendi had given up as hopeless. Even in the face of this problem Hobbes is not wdlling to abandon the fundamental principle that moveme nt is the sole reality. The movements of cor- poreariubstances are transmitted to the senses, w T hence they pass to the brain and from there to the heart. Here the movement is reflected, and the counter-movement, proceed- ing from the heart to the brain and thence to the peripheral organs, is the sensation. All the other psychical phenom- ena develop out of the movement of sensation by mechan- ical processes of a similar sort. The soul is thus no longer a particular kind of matter as in ancient materialism; it has become an effect of mechanical processes. Moreover, Hobbes does not start with the concept of the soul but with the elements of mental life. Here, too, the Jirst influence of empiricism makes itself felt. England, henceforth, remains theMiome of materialism. One of the best-known literary documents of the psychological materialism associated with the free-thought movement are Toland’s Letters to Serena, 1 Opera, Florence, 1725, II (2) 8, sect. Ill, t. VI, c. 3: “Qui sensibile gigni ex insensibilibus possit.” 38 HISTORY OF PSYCHOLOGY Sophia Charlotte, Queen of Prussia (1704), in which thought is described as an accompaniment of the material processes in the brain. The type of materialism under consideration is enriched by the founders of associational psychology, Hartley and Priestley. Hartley (1704-57) is the originator of the vibra- tion hypothesis according to which mental processes have as their physical counterparts specific vibrations of brain fibres. He did not, however, draw the materialistic conse- quences of this hypothesis, but confessed that the analysis of psychical processes must always yield psychical constit- uents, and that a sensation which is not capable of fur- ther analysis cannot be explained by movement. Priestley (1733-1804) developed these new materialistic presupposi- tions into a rounded system of psychology. He sees a proof for the identity of brain and mind in that uniform co- ordination in consequence of which all psychical phenom- ena, among which the associations of ideas form the most important role, are determined by brain vibrations. Without contributing to psychology any original points of view, mechanistic materialism, together with all it implied, passed over into the systems of Lamettrie and Holbach. At the same time we encounter here the transition to our final form of materialism, psychophysical materialism. (c) Psychophysical Materialism This form of materialism was introduced into psychology by Diderot, who held that some material process was in- volved in every act of sensation. It is true that in express- ing this thought he was not without forerunners, and there were other writers of his own period who agreed with him. The general background is furnished by the metaphysics of Spinoza, whose principles have influenced psychology in MONISM IN PSYCHOLOGY 39 very diverse ways. Maupertuis, too, had written of senti- ent atoms in an anonymous piece published in 1761, and in his Buck von der Natur, published in the same year, he ap- plied the principle of psychophysical parallelism throughout in connection with the discussion of voluntary movement. While his fantastic system permitted of only an occasional application of this principle, Diderot developed the psy- chological principles involved in parallelism with much clearness. Thus he accounted for the unity of conscious- ness by the supposition that the sentient particles of matter come into immediate contact with each other. From the spatial continuity of atoms follows the unity of the mental elements associated with them. The form of materialism under discussion has also influ- enced the most recent psychological movement in Germany, where we find indications of materialistic ways of thinking as early as the beginning of the eighteenth century. A much-discussed anonymous piece, Brief wechsel iiber die Seele (1713), which apparently originated under the influence of the English Enlightenment, defended the view that all sen- sations and ideas originate from movements of brain fibres (, fibris cerebri). In the eighteenth century, the century of the Enlightenment', a period so memorable for the history of our science, materialistic psychology was widely influ- enced by the presuppositions, borrowed from association psy- chology, of the dependence of psychical processes upon brain processes. 1 A deeper comprehension of the principle of psy- chophysical parallelism is revealed in many utterances of Kapt, which point to a pure monism. His criticism of ra- tional psychology indeed involved a demand for a purely empirical psychology, but he admitted the possibility, at the same time, of a solution of the fundamental metaphysical problem of psychology. If matter were a thing in itself, it 1 Cf. Chapter IV, 2, below. 40 HISTORY OF PSYCHOLOGY would, as a composite reality, be absolutely different from the soul, which is simple. But since it is merely an external phenomenon, it is possible to suppose that what appears to the physical senses as extended substance is endowed with thought which can be consciously apprehended by its own inner sense. That which in one relation is called corporeal would in another relation be conscious. 1 A new era in the history of materialistic psychology begins as a reaction to the philosophy of Romanticism, and develops hand in hand with the progress of natural science. The most influential representatives of this tendency in the lat- ter half of the nineteenth century were Moleschott and Buch- ner. Moleschott’s view approaches equative materialism, which identifies brain and mind, while Buchner contents himself with asserting the indissoluble connection between spirit and matter. Just how physical movement is trans- formed into consciousness is for him an irrelevant question. With all the emphasis which one finds here upon experience, there is a curious absence of any genuine psychological analy- sis. With a naivete which is nothing less than archaic, all conscious processes are classified under the common head of “thought.” Empirical psychology can, of course, not be built upon such foundations. Even the most profound thinker among these materialists, Czolbe (1819-73), who made the exclusion of the supersensible the fundamental principle of his system, abandoned all pretence of empirical investigation, losing himself in a maze of hypotheses con- cerning the sentiency of atoms, and arriving at a sort of world soul composed of vibrating atoms endowed with con- sciousness. It is only in the human organism that they con- solidate sufficiently to make individualized psychical life possible. The controversy over materialism in Germany differed 1 Kant, Kritik der reinen Vernunft, ed. Rosenkranz, p. 288. MONISM IN PSYCHOLOGY 41 from earlier controversies mainly in the influence of Dar- winism. On the whole, psychology profited but little from this controversy. In the far-ranging discussion regarding the nature of the soul between Carl Vogt and Rudolph Wag- ner, Virchow also took part. 1 The energy of soul substance or of psychical ether, he insisted, must ultimately be sus- ceptible of physical measurement. The controversy reached its climax in the association of natural scientists which con- vened in Munich in 1877, where Haeckel asserted that the cell was the basis of all psychical life. We must assume the existence of soul life in the cell, and, in order to carry the matter to a logical conclusion, attribute consciousness to atoms. This “ Plastidulseele,” as it was humorously called, was criticised with unsparing irony by Virchow. Thus psychological materialism in this final form either dropped back into the ways of thinking of older metaphysical systems, or else it recognized the principle of psychophys- ical parallelism and became a border problem of empirical psychology, as in Bastian, for example, in Germany, or in Herbert Spencer, in England. Materialistic presuppositions also occasionally developed into specifically modern ideas. A peculiar form of material- istic psychology was worked out by Jager, 2 a Darwinian zo- ologist of the old school, according to whom psychic vapors radiate from the body which affect the olfactory sense, and thus give rise to love, family and race solidarity, etc., in the percipient. 3 Jager’s ideas won some recognition, especially among the Darwinians, who hailed Jager’s efforts as the be- ginnings of a chemistry of the soul, but they were also sub- jected to much ridicule. Jager’s theories met with some favor outside of the exact sciences. Mantegazza, for ex- 1 Ges. Abh. z. vriss. Med., 1856, p. 17. 2 Jager, G., Die Entdeckung der Seele, III, 2d ed., 1880. 3 Cf. Rddl, Geschichte der biologischen Theorien, II, 1909, p. 435. 42 HISTORY OF PSYCHOLOGY ample, utilized them in his notorious work, Physiology of Love. They have to some extent been revived by J. Loeb, who attempted to construct a comparative psychology upon chemistry, and who saw in his theory of tropism the key to the elementary phenomena of life . 1 The discussion, how- ever, as will be seen, has now shifted completely from the field of metaphysics to that of physiology. A comparison of the various forms of materialistic psy- chology shows that they have developed in connection with different influences. In dualistic psychology, for example, we \ find a combination of popular ideas and religious demands; spiritualistic psychology has been very closely associated ; with the great philosophical systems; while, finally, material-^ istic psychology has always appeared concomitantly with ' natural science. These general influences have always dom- inated psychological reflection; we shall meet with them again as we seek to trace the various tendencies of empirical psychology. Dynamics of Living Matter, 1906. II. EMPIRICAL PSYCHOLOGY CHAPTER III DESCRIPTIVE PSYCHOLOGY Empirical psychology can be divided according to differ- ent points of view. Although its various tendencies agree among themselves as regards the proper point of departure for psychological investigation, namely, the testimony of introspection, they differ from each other partly as regards the principles to be employed in the analysis and combina- tion of psychical facts, partly as regards the exact scientific goal which empirical psychology should set for itself. The latter difference divides empirical psychology into two lead- ing types, descriptive psychology and explanatory psy- chology. To be sure, descriptive and explanatory psychol- ogy do not represent contradictory but supplementary points of view. Nevertheless, the preponderance of the one or the other method of procedure is usually sufficiently dis- tinct to keep the tendencies separate. The conceptual sep- aration of these two points of view has, of course, not taken place until comparatively recently. Some psychologists — Lipps, for example — have taken an extreme view of this relation and have declared the problem of explanatory as distinguished from descriptive psychology to be the estab- lishment of causal connection within reality, thus gaining a basis or substructure for the empirical data of consciousness . 1 The sharp opposition of the two tendencies seen here has de- 1 Leitfaden der Psychologie, 3d ed., 1909, p. 43. 44 HISTORY OF PSYCHOLOGY veloped out of an earlier status, where the contrast was not nearly so marked and where the descriptive type of psychology was on the whole the predominant one. Mean- while there are various points of contact between the two forms of psychology under consideration. Thus what is called intellectualism in psychology has often operated against an unbiassed study of the mental life. The ten- dency to intellectualize the mental processes, to force them into a conceptual system dominated by intellectual catego- ries, has characterized descriptive and explanatory psychol- ogy throughout . 1 Supported, on the one hand, by the ideas current in popular psychology and, on the other, by certain metaphysical presuppositions, intellectualism has made it- self felt both in faculty psychology and in association psy- chology. Descriptive psychology was for a long period dominated by prescientific conceptions. This period coincides in the main with that of faculty psychology. Reflection upon the question as to how psychical facts are known led to the psy- chology of the inner sense, which forms the starting-point for a number of tendencies in the modern phenomenology of consciousness. i. Period of Prescientific Concepts: The Doctrine of Mental Faculties Perhaps more than any other science, psychology has had to face and settle accounts with prescientific conceptions, such as one encounters at the threshold of every science. The terms of every-day speech which are used to designate cer- tain experiences are adopted uncritically both for purposes of description and of explanation. But explanation must 1 Cf. Wundt, “Logik u. Psychologie,” Zeitschrift fur padagogische Psy- chology u. Hygiene, 1910, pp. 1 ff. DESCRIPTIVE PSYCHOLOGY 45 always remain primitive and inadequate so long as the hasty descriptions of common usage are substituted for the gen- uine analysis of the phenomena concerned. Prior to every form of scientific psychology the terms soul, reason, will, and the like are already in common use. They serve the purposes of classification about in the same way that the terms light, sound, etc., serve to classify physical phenom- ena. Such rude classifications are indispensable for purposes of general orientation, and even scientific usage must begin with them. While, however, popular physical classifications have corresponded fairly well to the classifications which have resulted from a more exact analysis of physical phe- nomena, the needs which have been of influence in shaping the distinctions of popular psychology have not been quite the same as those which influence scientific psychology, so that a considerable discrepancy between the popular and the scientific classifications was bound to result. Most of the concepts in question show a considerable degree of generality, while appropriate designations for the more specific groups of mental phenomena, like certain kinds of simple feelings, are wanting altogether. It was the salient differences in complex experiences which first forced themselves upon the introspective attention. The gener- ality of the concepts thus originating favored the tendency to substantialize them, a tendency which is traceable to the earliest nature mythologies, from which the concepts in question passed over into metaphysical psychology. The traces are also revealed in the empirical applications which these concepts have received. The need for a rational com- prehension of psychical facts prompted the appropriation of these class designations and transformed them into powers or faculties which are supposed to produce the psychical facts to be explained. The notion of power is meanwhile still mythological in its significance. If human volition con- 46 HISTORY OF PSYCHOLOGY stituted the origin of the idea of power, and if power thus manifests itself in things as the human will manifests itself in actions, then the transformation into faculties, together with the personification implied in that, must find its justi- fication in the caprice with which psychical phenomena mani- fest themselves. Thus arose the concept of mental faculty, which, self-contradictory as it appears, was well adapted to account for psychical experiences as these presented them- selves to the primitive mind. Faculty psychology originally stood in intimate relation with the metaphysical doctrine of the parts of the soul. No- table beginnings of empirical psychology were made in the faculty psychology of Scholasticism. The psychology of the Renaissance, developing, as it does, in many directions, represents a transition to the faculty theories of modern psychology. The various forms of faculty psychology are meanwhile principally distinguishable on the basis of histor- ical epochs, a matter which is readily understood since the development of any new point of view would of itself lead psychology beyond prescientific conceptions and hence also beyond the point of view of faculty psychology. (a) The Doctrine of the Parts of the Soul j In its earliest form the doctrine of mental faculties is diffi- I cult to distinguish from the doctrine of the parts of the soul. The only thing possible for metaphysical psychology was to divide the soul in accordance with existing verbal distinc- tions. Such a partition of the soul could either take place upon the basis of empirical differences found among differ- ent psychical processes or else a gradation of these processes could be undertaken. The first principle of division depends, from our modern point of view, upon the fact that certain mental contents can be classed together in virtue of the pos- DESCRIPTIVE PSYCHOLOGY 47 sibility of passing from one to another of the contents within a group by intermediate gradations, whereas such a transi- tion is impossible between members of one group and those of another. Thus one can pass from one feeling to another through intermediate feelings, but one could by no possi- bility pass from, say, a feeling of unpleasantness to the sen- sation of blue. The second principle of division depends upon the observed fact that within a given group of more or less complex processes, as, for example, cognitive processes, a number of different steps or stages can be distinguished. Other classes of processes can be marked off on the basis of their objects or of their relation to other mental processes. 1 The first-mentioned and most commonly accepted ground of division was the one which forced itself first upon the attention. We meet it in the Pythagorean doctrine of the parts of the soul. It was here that Aresas of Croton in- vented the terminology later adopted by Plato. The well- known tripartite division of the soul into reason (to XoyiaTiicov) , will (to 0v/j.oet.8e;), and desire (to eTndvixrjrucov) were in Plato, of course, still derived from the idea of the mixture of the soul with the body in the sense of his meta- physical psychology. The Platonic division, however, is an anticipation of the later classification of psychological proc- esses into those of cognition, feeling, and desire. To these psychological distinctions corresponds a spa- tial separation of the various parts of the soul, with the vovs located in the head, the 6v fjuk in the breast, and the emOvfi-qTLKov in the lower part of the body. This locali- zation of the parts of the soul was widely accepted in the psychology of antiquity. Even Democritus, whose scien- tific attainments far exceeded those of his contemporaries, agrees in this respect with the traditional views, locating 1 For further particulars concerning principles of classification see Chapter VII, below. 48 HISTORY OF PSYCHOLOGY reflection in the brain, anger in the heart, and desire in the liver. z Plato apparently drew a further distinction within each of the parts of the three divisions of the soul. Each of the parts is characterized by a particular form of desire, the highest by Eros, the characteristic of the (jnX6ao(po<; . Each, too, is characterized by a particular kind of pleasure whose grade is determined by the value of the particular part of the soul to which it belongs. There are also suggestions of a relation between sense-perception and desire ( hnOv^Tucov ), and between opinion (8oga) and 6v/ioei,8es. Here the second principle of division makes itself felt in so far as different grades are assumed within the departments of cognition, feeling, and desire. Side by side with these distinctions is also found the distinction — a direct outgrowth of metaphysical dualism— between the higher and the lower parts of the soul, a division plainly based upon the various grades of conscious processes and brought into harmony with the former by the fact that the lower part of the soul as sensibility comprehends both desire and feeling. The doctrine of the parts of the soul is in Aristotle trans- formed into the doctrine of mental faculties. Aristotle lo- cated the soul in the heart, as the centre of the body, an idea which for a long time competed successfully with the scientific doctrine that the brain was the seat of psychi- cal phenomena. The latter doctrine, already held by the physicians of ancient Egypt, was eventually recovered by Herophilus of Alexandria and Galen. The older spatial separation gave way in Aristotle to conceptual distinctions which are based upon the successive stages of biological development. Experience reveals four such stages: (1) growth and nutrition (to Opeirrucov), (2) sensation and im- agination ( aladrjTiKov and fyavTaarucov) , (3) conation and DESCRIPTIVE PSYCHOLOGY 49 locomotion (opefCTt/cdv and kiv^tucov /card, t ov t ottov), and (4) thought (Siavor/Tucov) . Conation, however, which oc- casionally is divided into desire (e7 tlOv^lo), feeling (dvpos), and will (/3ov\T)cn<;), and locomotion are in the main subordinated to sensation as impulse and to thought as will, so that the scheme reduces to a tripartite division, the nutritive, sensitive, and rational soul. The plant possesses only the first, the animal the first and the second, while man possesses all three. The Platonic bipartite division here reasserts itself, since the two lower faculties present a com- mon antithesis to reason (SiavorjTucdv) . Although the Aristotelian system offers no new distinc- tions, it nevertheless possesses two advantages. In the first place, t he idea of the unity of the soul is asserted, since neither of the facidties mentioned is capable of operating in independence of the rest. Secondly, there is a clear sugges- tion of the evolutionary point of view. The rough distinc- tions proposed do not, of course, completely solve the prob- lem of classification; but with the contention that the higher faculties presuppose the lower is combined the thought that the human soul stands in the same relation to the animal soul as the higher faculties stand to the lower, so that here, too, the unifying idea of evolution tends to bridge over the dualism which would otherwise exist. It is the latter idea especially which was followed out in Patristic philosophy. Dicsearchus even refused to recognize any longer the distinction between the rational soul and the sensory functions. Diodorus of Tyre supported him in this, but associated both functions with an identical sub- stance, ether. The Stoics, indeed, possessed in pneuma the physical principle of unity of the soul life, but they did not hesitate to grant the existence, at the same time, of an in- creasing number of mental faculties. The Stoics were, per- haps, the first to recognize the five senses as parts or facul-. 50 HISTORY OF PSYCHOLOGY ties of the soul, i. e., of the pneuma. Adding to these the power of reproduction, of speech, and of reason, there re- sulted a total of eight faculties, with the ruling faculty, rea- son (r/yeyovucdv ) , at the head. In later Stoicism and in the earlier developments of Neo-Platonism, psychology merely repeats the Platonic and Aristotelian distinctions. The doubtful comparison of the soul and its faculties to a house and its inmates originated with Philo. Patristic philosophy, whose metaphysical psychology un- avoidably involved the doctrine of the unity of the soul, appears to have been only slightly influenced by the faculty psychology. Tertullian opposed the Platonic division of the soul into parts, pointing out convincingly that the difference between the higher and the lower faculties of knowledge rested upon the nature of the objects of knowledge, the cog- nitive soul being equally active in all cases, and he compared the distribution of the soul throughout the body to the divi- sion of a column of air as it passes into the different pipes of an organ. To be sure, the tripartite division of Aristotle reappears in Gregory of Nyssa, the parts of the soul being expressly designated as mental faculties. On the other side, however, is the great authority of Augustine, who insists | upon the strict unity of the soul. It is not until the period ' of Scholasticism that the Aristotelian doctrine of mental faculties is again revived; here, however, it is combined with sundry efforts at purely empirical investigation, a fact which differentiates the faculty psychology of Scholasticism from all previous types. (b) The Beginnings of Empirical Psychology in Scholasticism j Scholasticism seems often at first sight to be merely a synonym for useless dialectical controversies. Nothing is more improbable, however, than the belief that men’s desire DESCRIPTIVE PSYCHOLOGY 51 for empirical knowledge should have remained latent for a period of history of the extent of Scholasticism. In the absence of an interest in external nature, the knowledge of which, at least during the Platonic period of Scholasticism, was largely dependent upon the fantastic nature philosophy of Timeeus, men’s interest in empirical knowledge turned the more exclusively to the phenomena of the inner life. This led to the beginnings of an empirical psychology whose justification is recognized in the oft-repeated statement that the knowledge of reality divides into two branches, physica corporis and physica anirnce. Empirical psychology was, of course, developed in the manner of the time. Psychology, among other things, is not content to describe and classify mental processes but seeks to view them teleologically as well. It is the history of the soul which is to be expounded, and the Scholastic writers accordingly appear not as cau- tious scientists but as pious souls yearning to comprehend the divine mysteries and thus to share in the divine favor. The first beginnings of psychological reflection from an'N empirical point of view are to be found in the older nomi- nalism . 1 The author of the conceptualistic treatise De In- telledibus teaches the close connection between sense-per- ception and thought ( sensus and intellectus) . 2 Between these stands the sensuous imagination (imaginatio) , whose contents, like those of sense-perception itself, are said to be indistinct ( confusa animcB perceptio ). One calls to mind here the role which the alleged indistinctness of sense-per- ception played in the theory of knowledge subsequent to Descartes and the reflex influence it exerted upon physio- logical psychology. Already in the tenth century the \ three higher cognitive faculties ( intellectus , ratio, mens) are de- scribed as sensus animi by a nominalistic glossarist; the fac- 1 Cf. Siebeck, op. cit., I, pp. 384 ff. 2 See Cousin’s edition of Abelard, II, p. 732. \J 52 HISTORY OF PSYCHOLOGY ulties of the soul are localized in the three ventricles of the brain ( folliculi ), in which the principalitas vitas, sensus, and motus have their seat . 1 Nevertheless, the traditional lore from which the Occident benefited before the introduction of Arabian philosophy was sufficiently meagre. The teaching of Damascenus concerning the mental faculties and their respective functions seems to have been held in peculiar esteem . 2 This writer contents himself, in the sketch referred to, with a meagre enumeration of the best-known psychical states; in the discussion of the will, for example, six leading concepts ( consilium , judicium, sententia, eledio, impulsus, usus ) are dismissed with a few lines. The influence of Arabian culture upon psychology was mediated through the translations and adaptations of Con- stantine of Carthage, who flourished in the second half of the eleventh century . 3 Constantine’s view of the nature of the soul represents a superficial admixture of Aristotelian and Platonic conceptions . 4 The soul is treated as specifi- cally different from the body. It is the primary cause of life, the secondary being pneuma, which acts by means of special physiological processes. The different manifesta- tions of the function of cognition correspond to the anatomi- cal divisions of the brain. The pneuma of the anterior ven- tricle yields sensation and perception, that of the posterior, movement and memory. In detail, his exposition resembles fairly closely that of Galen. Among those most immedi- ately influenced by Constantine is William of Conches . 5 His definition of the soul as spiritus corpori conjundus is, indeed, meagre enough. Of real importance, however, are the unmistakable beginnings of genetic psychology made by 1 Barach, Zur Geschichte d. Nominalismus von Roszellin, 1866, pp. 9 ff. 2 John Damascenus, De ortliod. fid., II, cap. 13 ff. 3 Siebeck, op. dt., I, pp. 527 ff. * De commun. medic, cogn. necess. loc. (ed. Bas.), IV, 1. 6 Siebeck, op. dt., I, pp. 531 ff. DESCRIPTIVE PSYCHOLOGY 53 this writer. A number of faculties mediate between percep- tion and understanding {ratio). The understanding, which knows physical causes, becomes intelligence when knowledge extends to the non-physical, and this development has actu- ally taken place in the process of historical evolution. 1 In John of Salisbury we meet a similar effort to connect genetic ideas with a fundamentally Platonic theory of the nature of the soul. 2 His attempt to exhibit the development of the various grades of mental functions from sense-percep- tion is a partial anticipation of the type of genetic-sensual- istic psychology destined later to become so familiar on British soil. The complete execution of this task was ren- dered impossible, of course, by the limited knowledge of the time. Sense-perception is called a combination of sensa- tion and judgment. 3 A series of higher judgments leads up to conviction (ratio) which has its seat in the brain between imagination ( cella phantastica) and memory. As ratio is superior to the senses, it is in turn subordinated to intellect, which, in spite of the divine enlightenment it receives, de- pends upon sense-perception. Empirical psychology did not pass beyond these beginnings until its contact with Arabian science. Avicenna (980-1037), the celebrated teacher of philosophy and medicine at Ispahan, left behind him a body ol empirical psychology which became the common heritage of the vari- ous branches of Scholasticism. 4 He separated philosophical psychology from medical psychology, although his empirical investigations do not carry him far beyond an elaborate sys- tem of classification. In his theory of sensation, for example, he distinguishes eight pairs of contrasting sense qualities, 1 See Cousin, CEuvr. ined. d’Ab., pp. 671 ff. 2 Siebeck, op. cit., I, pp. 518 ff. 3 Primum judicium viget in sensu ; Metalogicus, 1159-60, IV, 11, p. 892. 4 Siebeck, op. cit., II, pp. 22 ff. 54 HISTORY OF PSYCHOLOGY four for the sense of touch, and one for each of the remaining senses. The various parts of the soul are subdivided also, while each of the three kinds of anima vegetativa is in turn split up into smaller divisions. The relation of body and soul is conceived from a peculiar teleological point of view. Each soul, namely, belongs to that particular body for which it is best fitted. The attempt to construct a genetic concep- tion is suggested by the doctrine that the principles of knowl- edge, although innate, can develop only in the wake of per- ception. To be sure, this reflection loses much of its force through the assumption that the senses are capable only of sensation, true knowledge being the exclusive product of the soul. With the incorporation of the views of Avicenna into the theological system of Alexander of Hales (d. 1245) 1 we reach the point in mediaeval psychology where the older Pla- tonic characterizations yield before the influence of Aristotle. Alexander again distinguished mental faculties from vital functions, defining the soul as a thinking and active sub- stance whose continuous activity constitutes life. The orig- inal active power of the soul is desire (appetitus), which has as its aim the unification of potentiality and actuality. More closely related to the ancient models, the exposition of Thomas Aquinas adds to the Aristotelian system only an elaborate conceptual apparatus. The relation of the soul to the mental faculties is the same as that of substance and accident. The soul alone is the subject of reason and the rational will, while the organism as a whole serves as the basis of the vegetative and the sensitive functions. The con- trast between the higher and the lower functions of the soul thus reappears in this rationalistic form. The gradually awakening epistemological interest of the time finds expression in the psychological theories of Roger 1 Siebeck, op. cit., II, pp. 180 ff. DESCRIPTIVE PSYCHOLOGY 55 Bacon . 1 The lower and the higher faculties of cognition are for him two different stages of the same inner experience which arises partly out of sense-impressions and is partly of a transcendent origin. Neither are intellect and will two separate powers, but functions, rather, of one and the same fundamental psychical faculty, a doctrine which makes Ba- con the immediate predecessor of a more influential writer, Duns Scotus. The most thoroughgoing efforts to arrive at a psychological theory of the process of knowledge, however, were made by Occam . 2 The external object, in virtue of its own peculiar quality, gives rise to a sense-impression which is perceived by the sensuous soul ( apparitio ). Through an act of abstraction, which is a function of the inner sense (phantasticum ) , the conscious perception becomes an inner image. Sense -perceptions and their reproductions are now elaborated by the intellect, which, through a process of ab- straction, forms concepts and judgments, affirmative and negative judgments being formed through the co-operation of the will. This psycho-epistemological sketch serves to illustrate how far these ancient thinkers, although laboring under the limitations of the faculty psychology with its bar- ren intellectualism, succeeded in analyzing an important process like that of cognition. Whether we are to see in the psychology of Scholasticism as a whole the final phases of the tradition of antiquity or the beginnings of modern empirical psychology need not be de- cided here. In any case, the psychology of the Renaissance, to which we now turn, presents a different picture in both respects. 1 Siebeck, op. cit., Ill, pp. 177 ff. 2 Siebeck, op. cit., X, pp. 317 ff. 56 HISTORY OF PSYCHOLOGY (c) The Psychology of the Renaissance Z One of the best evidences of the stimulating effect upon / psychology produced by the vital participation in all phases of life so characteristic of the period of the Renaissance is the psychology of Ludovicus Vives (1492-1540). His prin- cipal work, Be Anima et Vita (Bruges, 1538), which exerted a large influence upon the psychological theories of the six- teenth and seventeenth centuries, is characterized by a defi- / nitely empirical point of view. The task of psychology is to discover the manner of the soul’s activity. Psychological description must be rigorously faithful to experience. Al- though the investigation still employs the tools and concep- tions of faculty psychology, there are suggestions of a sort / of physiological psychology which brings the concepts of soul and body into close relation. Vives, moreover, proves himself emancipated from the Aristotelian school by treat- ing the brain as the seat of psychical processes. The influence of the new knowledge upon the various ten- dencies and directions of ancient psychology is also clearly discernible. With the recrudescence of Platonic psychology the whole swarm of ancient psychological conceptions again became current, and in their mutual contradiction the scep- ticism of the period found a ready support. In the chapter On the Soul in his book, Be Incertitudine et Vanitate Scien- tiarum (1527), a work characteristic of this tendency, Agrippa of Nettesheym makes a collection of these contradic- tions; but, while referring to the fiendish Aristotle and the divine Plato, he himself sceptically refrains from expressing any opinion of his own concerning the soul. More definite opinions are expressed by certain philoso- phizing physicians of the time of Paracelsus, whose psychol- ogy represents a fusion of traditional conceptions with the new DESCRIPTIVE PSYCHOLOGY 57 doctrine of Archeus. Paracelsus himself fantastically trans- formed many of the older teachings. He abandoned the time-honored doctrine of temperaments taught by Galen, substituting for the four elements the main principles of alchemy, sulphur, salt, and mercury. This tendency is also represented by the chemist Van Helmont, who distinguishes the sensitive soul ( anima sensitiva), whose seat is the duum- virate, from spirit (mens), an imperishable substance, whose attributes are intelledus, voluntas, and amor } The manner in which this part of the soul, which is subject to neither fatigue nor disease, can act upon the others is left unde- termined. 1 2 Connected only slightly with this questionable theoretical 1 psychology, a secular Renaissance psychology is developed which we can recognize as a forerunner of the empirical ps^hology of the eighteenth century. The doctrines of ( temperaments, astrology, and physiognomy here stand in *^the service of a realistic characterology. Juan Huarte’s Examen de ingenios (1575) thus teaches an individual psy- chology which seeks to bring the mental traits of the indi- vidual into relation with bodily constitution. With the French psychologists of this period, beginning with Michel de Montaigne (1580), this individual psychology tends more and more to become practical anthropology. 3 More important than these fantastic or superstitious ideas and this secular psychology is the controversy between the traditional faculty psychology and the new conception of soul substance which was already preparing in the Marburg school. Casmann 4 does not, indeed, explain the relation be- 1 Cf. Strunz, “Die Psychologie des Joh. Bapt. van Helmont in ihren Grundlagen,” Zeitschrift f. Phil. u. phil. Kritik, CXXV, 1905, p. 2. 2 Van Helmont, Imago Mentis, § 7, Opera, 1648. 3 Cf. with this the pregnant discussion of M. Dessoir, Gesch. d. n. d. Psychologie, I, 2d ed., 1897, pp. 47 ff. 1 Psychologia anthropologica, 1594. 58 HISTORY OF PSYCHOLOGY / / tween a unitary soul and a plurality of faculties; nevertheless, I he raises the objection that each faculty requires a second I faculty for the explanation of its peculiar functions. Neither did the psychology of Descartes tolerate a multiplicity of i separate faculties, for the soul has only a single faculty, / that of thought; and the distinction of the various thought I processes, which all rest upon the fundamental distinction between active and passive thought, does not in any way jeopardize the underlying unity. The popular distinction between a higher and a lower mental faculty Descartes, clinging closely to the metaphysical presuppositions of his ' psychology, explains by a supposed conflict between them i in the pineal gland in which a movement set up by the ani- mal spirits in the body meets another movement set up by the soul through the activity of the will. For the rest, the distinction between power and faculty does not as yet Aist in the Cartesian psychology, while later the concept? of psychical powers and psychical faculties are used inter- changeably, a convincing illustration of the fact that in the history of psychology distinctions of terminology and of fact are difficult to keep separated . 1 r ■ (d) The Newer Faculty Psychology j It was John Locke who, writing from the standpoint of empirical psychology, was the first to urge emphatically against faculty psychology those objections which have become commonplaces in modern psychology. In the dis- cussion of the freedom of the will he pointed out the futility of the attempt to explain freedom by reference to a faculty \of volition; as well call in a vocal faculty to explain singing, or a faculty of dancing to explain dancing. Psychology 'See the following from the Cartesian Clauberg: “Vis facultas po- tentia quse nihil aliud quam non repugnantia ad agendum.” DESCRIPTIVE PSYCHOLOGY 59 gained little, however, through Locke’s substitution of powers for faculties. This is evidenced in Locke himself by his curi- ous oversight of the mutual interaction of mental processes. The separate powers no more influence one another than the power to sing, for example, influences the power to dance. In the enumeration of mental powers, moreover, Locke was hardly less generous than faculty psychology. Leibniz transformed the concept of faculty into that of ac- tual tendency, and he was able to dispense with the swarm of faculties the more easily inasmuch as his doctrine of the persistence of petites perceptions permitted him to refer what were apparently novel phenomena to their temporal ante- cedents. In Christian Wolff (1679-1754), who first employed the term mental faculty, the Leibnizian tendency was directly con^nued. 1 In his rational psychology he designates the power of representation (vis reprcesentativa ) as the funda- mental power of the soul. This is the sufficient reason for every mental phenomenon, in so far as it transforms the possibilities of psychical processes, i. e., the faculties, into actualities. On the ground of the conceptual discriminations attempted by Leibniz, therefore, power and faculty are kept distinct, thus resulting in a distinction which goes back directly to the Aristotelian Surn/zt? and ivepyeca. But Wolff' does not remain long upon these heights of abstrac- tion. The faculties, which in the beginning are mere possi- bilities of mental processes, now become attributes of the soul ; at first mere nudce agendi possibilitates, they now turn into the more substantial forms of natural dispositions, so much so that their relation to the mind can be compared with the relation of bodily organs to the body. The classifi- cation of these faculties is based upon the overlapping oppo- 1 Wolff, Psychologia rationalis, 1734; Psychologia empirica, 1732. The difference between the two treatises is less than the titles would suggest. 60 HISTORY OF PSYCHOLOGY sites of cognition— desire, and of sense — reason. In the first pair of faculties the Leibnizian distinction between cognition and appetition as attributes of the monad, a distinction to which Wolff always adhered, is clearly discernible. While cognition and desire (the latter term also includes feeling) are here juxtaposed without any difference of valuation, the second principal division yields a lower and a higher faculty of cognition, as also a lower and a higher faculty of desire. In the subdivisions of these four principal faculties, mean- while, there is not the slightest attempt at system. Even the most complex mental faculties are “explained” by in- voking the magic words mental faculty. In his attempt to explain the interaction of the various faculties each faculty functioned as a sort of intelligence or, at least, had enough in common with the faculty of intelligence to render intelli- gent co-operation among the faculties possible. The parl- ous grades of intelligence, furthermore, could readily be rep- resented on the analogy of the Leibnizian distinction between clear and obscure perceptions. '/There is not a writer in the history of faculty psychology after Aristotle who gives so much attention to mental facul- ties as Wolff. With Descartes the contrast between the active and passive mental processes had received the prime emphasis; Locke had designated sensation and reflection as distinct sources of knowledge; in Leibniz, finally, the princi- ple of psychological explanation of primary importance was the power of representation. It must, of course, be remem- bered that Wolff passed into only a part of the Aristotelian j heritage, which had been the common possession of scientific thought for so many centuries. He was incapable of the painstaking and ingenious methods of investigation charac- teristic of Aristotle. His empirical psychology, in fact, is little more than a questionable determination of the number and the character of mental faculties. DESCRIPTIVE PSYCHOLOGY 61 A In the Wolffian school the doctrines of faculty psychology were extended to the cognate sciences, like ethics, in the ra- tional utilitarianism of which it readily struck root, and aesthetics, which contented itself for a long period with call- ing the creative imagination a lower order of the faculty of cognition. In spite of the arbitrary manner in which they were deduced, the Wolffian distinctions long maintained their influence. When we come to examine in detail the faculty psychology of the eighteenth century emanating from Wolff we find it to be an achievement of doubtful value. It must not be forgotten, however, that the real aim was to construct an empirical psychology which should discover introspec- tively the contents of consciousness and then discover the elementary powers of which they are the manifestations. The methods of description and classification employed here were, as in many other branches of psychology, modelled after the methods of the natural sciences. It will be remem-/ bered that the eighteenth century was the century of those : descriptive sciences in which Linne and Buffon were mas- ters. To be sure, attempts at explanation in the field of psychology could not but have meagre results. The follow- ing is a typical example: If the power of imagination com- bines with the understanding, the creative faculty results; if it combines with reason, we get the power of anticipation, etc. The attempt to explain, to reduce the complex to the simple, is sufficiently commendable; but the actual explana- tion is undertaken with methods wholly insufficient for the purpose. Even the opposition to the Wolffian psychology did not succeed in freeing itself from the domination of the con- ceptions of the school psychology. Crusius attacked the doctrine of mental faculties in his work, Entwurf der notwen- digen Vernunftwahrheiten (1745), asserting that they were merely so many arbitrarily abstracted powers which made a 62 HISTORY OF PSYCHOLOGY purely causal explanation impossible. To meet the latter de- mand, he assumed actual powers in the soul substance which itself remained simple. There are mental powers of first order, like consciousness and sensation; of the second order, like imagination and the capacity for incomplete ideas. In spite of the strong emphasis upon causal explanation, these determinations are still distinctly reminiscent of the point of view of the faculty psychology. The psychological disciples of Bonnet, men like Irwing, Lossius, and Hissmann, schooled as they were in the methods of physiology, passed a more effective criticism upon the old doctrine of mental faculties. They were themselves, however, not free from the inclina- tion to explain the various conscious processes by reference to some single fundamental power. As a rule, sensation, which was thought of as a reaction of the soul to the exci- tation of nerve fibres, figured as such a fundamental power. Tetens (1736-1805) criticised this view on the ground that perception and judgment were thus treated as belonging on the same plane as sensation, while he himself held that sen- sation, perception, and thought were distinguished only in the degree of self-activity which the soul displayed. Tetens, meanwhile, made an important contribution to the school psychology. 1 He effected a breach in the Wolffian scheme by the addition of a new faculty, that of feeling, to those sanctioned by the Wolffian tradition. * Tetens proposed a new pair of fundamental mental activities. In his attempt to “reduce the various capacities to the simplest faculties) and to penetrate to the primary origins of these faculties in some fundamental power,” he comes upon the opposites of receptivity and activity. The first is feeling, the second embraces the various activities of will, the inner activities of idea and thought as well as the outer. Thus originated the tripartite division of feeling, cognition, and will, which was destined to dominate psychology for a long time to come. 1 Versuche uber die menschliche Natur, 1776-7, pp. 4, 7. DESCRIPTIVE PSYCHOLOGY 63 The rationalistic origin of the scheme is evident from the description of feeling, ideation, and thought as phases or subdivisions of the general faculty of cognition. Both of the above classifications meet us again in Kant. Sense and understanding, the receptive and the spontaneous sides of mental life, appear as lower and higher faculties of cognition. Cognition, feeling, and desire, on the other side, appear as three fundamental faculties, separate and irre- ducible. The Leibnizian distinction between faculty and power, on the other hand, disappears . 1 Furthermore, Kant proposes, as correlatives of concept, judgment, and conclu- sion in logic, the trichotomy of the higher faculty of cog- nition into understanding, reason, and judgment. For the relation of these three phases of the higher faculty of cog- nition to the principal faculties of the mind mentioned above, the relation of reason to the faculty of desire appears to have been normative. Reason, as the faculty of ideas, could have a constitutive significance only in the sphere of practical conduct. Since the understanding coincided with the fac- ulty of cognition, feeling naturally came under the faculty of judgment. In so far as this schematization took into account only the higher manifestations of the faculties concerned, it exercised an unfavorable influence upon the psychological treatment of the three fundamental faculties. Furthermore, the sharp separation of the fundamental fac- ulties obscured the fact of their essential unity and the fruitless interaction of faculties everywhere took the place of the actual phenomena of the mental life. Fortunately, Kant did not adhere to the schematism of the three Critiques in his principal psychological work, Anthropologie, but pre- sented instead a body of practical psychology which he had inherited from the Enlightenment and which is still worthy of study to-day. The Kantian faculty psychology was continued by his 1 Cf., e. g., Krug, Philosophisches Lexikon (1827-34), article “Kraft.” 64 HISTORY OF PSYCHOLOGY school. K. L. Reinhold sought to explain the several varie- ties of the faculty of cognition by reference to the faculty of ideation or representation. Representation without a fac- ulty of representation is to him unthinkable. He even be- lieved himself to be acting in particular sympathy with the spirit of Kant when he substituted the investigation of men- tal faculties for the investigation of the mind itself. For the same reason he keeps in strict separation the representing subject from the faculty of representation. The former de- termines the attributes of the faculty of representation merely in a logical, not in a real sense. J. F. Fries (1773-1843) in- sisted upon a sharp separation of philosophical anthropology and empirical psychology. The latter is an experimental physics of the inner life, whereas the former is a theory of this life, bearing about the same relation to empirical psy- chology as the philosophy of nature holds to physics. Fries grants to the usual conceptual determinations of mental faculties only a descriptive significance and demands their proof by philosophical anthropology. These faculties must, furthermore, be subordinated to general laws. 1 All causal relations of inner experience must be ascribed to a faculty as cause, not to an activity as its manifestation. So long as the activity of a faculty consists only in modifying other faculties in respect to their manifestations, as will, e. g., acts upon attention, they are intermediate faculties. But they themselves have as their ground the primary faculties which manifest themselves on their own account and act according to a law of their own activity, as, e. g., thought and cognition. Nevertheless, mental faculties are not sus- ceptible of classification as are, for example, plants and ani- mals, for all the fundamental dispositions are active in ev- ery vital function, only in different degrees. The difficulty growing out of this conception Fries attempts to meet with 1 Neue Kritik der Vernunft, 1807, §§ 5-8. DESCRIPTIVE PSYCHOLOGY 65 his doctrine of the stages of mental development. There are distinguishable in each of the three fundamental faculties three stages, sense, habit, and understanding. If we add to these the two fundamental opposites of spontaneity and re- ceptivity, which repeat themselves at every stage of develop- ment, we see how prolix the faculty psychology again be- comes in the hands of a man who had come to understand the inadequacy of it in its traditional form. The theory of faculties is so natural as an explanatory hypothesis that we can trace its influence even in tenden- cies of modern psychology not directly dependent upon the traditional sources. The so-called psychological school in France, for example, bears the impress of the faculty psy- chology during the first third of the nineteenth century. It is true that Jouffroy demanded the separation of psychology both from philosophy and from physiology. His own psy- chological observation, however, offers little that is new, and his assumption of six original mental faculties differs from the customary classification only in the systematic character of his own scheme. The case is similar with the celebrated physicist and student of the classification of the sciences, Ampere, although he does, of course, make an attempt to explain the connection of psychical processes by his theory of “concretions,” the theory that sensations spontaneously combine with remembered previous impressions to form groups or “concretions.” The decisive step in the history of faculty psychology was destined to be taken in Germany. Faculty psychology had already come in for its share of criticism in the reaction to the Kantian system, as in the case of Schulze-/Enesidemus, who characterized the faculty theory as a mythological treat- ment of psychology. The real turning-point, however, in the history of the faculty theory was signalized by Herbart’s memorable criticism. There are two principal objections 66 HISTORY OF PSYCHOLOGY /hich remove the foundations from the faculty theory. The first is that the mental faculties are mere class concepts which are derived from experience by a process of provisional ab- straction and cannot rightly be raised to the dignity of fundamental powers. In the second place, mental faculties are nothing more than possibilities, which are not found among the facts of inner experience. For it is only the par- ticular idea, not a faculty of ideation, the particular feeling, not a faculty of feeling, which forms the content of our actual experience. But from the mere possibility the real happen- ing can never be derived. The first of these objections applies primarily to the doctrine of the plurality of separate faculties. There is a certain relationship, indeed, between the psychological class concept and other classifications, such as have been formed, for example, in the history of the life sciences. How rich, for example, was the physiology of Romanticism in organ-building powers ! In this respect psychology only shares the fate of all the other sciences. But, whereas the expanding knowledge of facts leads to a re- duction of such superfluous notions of power in the natural sciences, faculty psychology demands their indefinite mul- tiplication. The faculty of memory, for example, divides into a whole series of special memories, such as verbal mem- ory, memories for numbers, persons, etc., which eventually turn out to be as different from one another as the faculty of memory is different from that of imagination. The sec- ond objection attacks the notion of faculty directly. Her- bart proposes to substitute for it the notion of power, which differs from faculty in the respect that it arises as a neces- sary result of the appropriate conditions. We thus arrive at the most important point of view in which explanatory psychology goes beyond a merely descriptive psychology. In the faculty psychology mental faculties have free play, but when the notion of faculties has once fallen to the DESCRIPTIVE PSYCHOLOGY 67 ground the question as to the conditions under which given kinds of mental processes regularly run their course can arise. One last phase of the faculty psychology remains to be mentioned. F. E. Beneke (1798-1854) made the singular at- tempt to bring about the dissolution of faculty psychology by giving the tendency to unlimited specialization of faculties \ unrestricted play. The idea that every new mental process meant the development of another specific faculty modi- fied the whole conception of mental faculties in a peculiar way. Faculties are for Beneke no longer mere empty pos- sibilities. They rather stand for an undetermined psy- chical occurrence within the sphere of the unconscious, which occasionally enters consciousness. They are also described as tendencies which seek realization through sensation. Thus Beneke, although in his method more nearly allied to the psychology of the inner sense, approaches Herbart, whose ideas are often merely couched in a different terminology. In this singular manner two tendencies so opposite as the faculty psychology and psychical mechanics meet each other. Beneke’s primitive faculties are, taken fundamentally, Her- bart’s simple representations. Corresponding to the fusions and complications in Herbart, we have, in Beneke, the flow- ing together and the flowing through each other, in opposite directions, of the mobile elements of the soul. The power of the primitive faculty to cause itself to be filled and filled to overflowing, about like an empty vessel, is, of course, an idea peculiar to Beneke. There is little that is pleasing in the influence exerted upon the faculty psychology by the philosophical systems of Schelling and Hegel. If one takes up, for example, the Vorlesungen iiber Psyckologie of C. G. Carus (1831), one, in- deed, finds the author renouncing the “polytheism” of mental faculties and extolling the genetic method, but the latter is little more than an enumeration of the various psycho- 68 HISTORY OF PSYCHOLOGY logical phenomena which run their course in the history of the individual’s life. The apparent derivations are in re- ality nothing more than naive descriptions, and the analo- gies which are drawn between the mind and processes in nature, such as plant growth, are still more superficial. G. H. von Schubert also, in his Geschichte der Seele, contents himself with an exposition, aided by analogies with the animal organism, of the fundamental tendencies of mental activity, unconcerned to make a single psychological analysis. It was a characteristic assertion of Hegel’s that the psy- chological works of Aristotle continued to be the most im- portant, if not the only, work of speculative interest on the subject . 1 The only contribution of his own was to render fluid the Aristotelian faculties by the melting process of his own dialectic. The Hegelian psychology, as this was de- veloped in the spirit of Hegel by Rosenkranz, Michelet, and Erdmann, was sharply criticised by F. Exner , 2 who charged that this mechanical system meant a relapse of psychology even beyond Wolff himself. It is in this criticism that we see scientific thought making a determined stand against the speculative thought of the past. With this the faculty psychology may be said to have come to a definite end. Its long reign illustrates how tar- dily exact thought turned its attention to the actual psychi- cal facts embedded in prescientific conceptions. Faculty psychology ignored the fact, particularly, that through the fusion of simple processes combinations which are qualita- tively novel can arise. It acknowledged only the innate fac- ulties and the empirical contents of the mind with which they work. Thus almost the whole psychology of Greek an- tiquity started with the assumption that mental contents 1 Enzyklopadie, 1817, § 378. 2 Die Psychologie der Hegelschen Schule, beurteilt von Dr. F. Exner , 1842. DESCRIPTIVE PSYCHOLOGY 69 either originate in sense-perception or that they are an in- nate possession of the soul. The most significant testimony of this is Plato’s theory of ideas, that mystical recollection by the soul of contents which could, according to their def- inition, not have originated in experience. Although this alternative was probably primarily of an epistemological origin, it dominated psychology for a long period. To over- come it required a methodological apparatus which was im- possible until the advent of analytic psychology. Faculty psychology, meanwhile, has the lasting merit of having anticipated, in a general way, the aims of descriptive psy- chology and, furthermore, of having occupied itself with a problem with which every system of psychology must deal, that of the classification of mental processes. It was faculty psychology that drew the principal distinctions out of which the classifications of analytical psychology were to grow. 2 . The Psychology of the Inner Sense Opposed to faculty psychology are all systems of psychol- ogy which employ in common some form of analysis. For it is through the analysis of phenomena that prescientific concepts become scientific concepts. Psychological analysis, however, has a uniqueness which sets it off from other forms. The data of psychology, namely, have the peculiarity which we designate by calling them experiences, without being able to give a more definite description of them. With the attempt to lay hold upon these data the fundamental dis- tinction between physical and psychical phenomena became/ apparent. Introspection was found to be a wholly different process from the observation of external phenomena, so that the attempt to analyze mental experiences led to a sharp separation between outer and inner experience. The first demand of psychological description was thus satisfied. But 70 HISTORY OF PSYCHOLOGY the particular form which the efforts of descriptive psy- chology took, and in which it superseded the older faculty psychology, depended upon a still more general aspect of thought of a more scientific sort. For to the stage of the classification of phenomena there corresponds some consider- ation as to methods of observation. Thus, for example, the philosophy of nature of antiquity, which, in contrast with the mythological interpretation of nature, already under- took a derivation of complex phenomena from more simple ones, early occupied itself with theories, primitive enough, to be sure, of sense-perception. In a similar manner, analysis within the sphere of the psychical is preceded by reflections upon the peculiar nature of inner perception. In analogy to the outer senses the term “inner sense” became domes- ticated as a term for this species of perception. Now, if the inner sense is to be directed toward specific objects, as the analogy to the outer sense suggested, it is cognitive proc- esses which lend themselves most readily to introspective observation. A psychology whose analyses depend upon the peculiarites of such an inner sense naturally developed from the very outset a tendency toward intellectualism. When such an intellectuaiistic psychology combined with faculty psychology, logical reflections would take the place of psychological processes and psychology relapse into a prescientific stage, or else become dominated by a meta- physical conception of the soul, as it was, for instance, in the case of the rational psychology of the eighteenth century. Inhere is a second reason why cognitive processes, par- ticularly perception or ideation, should become the special Subject-matter of the psychology of the inner sense. It is in connection with these that the fact is most distinctly ob- servable that, while ideation is always directed toward an object, the process of ideation can itself become the object of introspective observation. In the case of a feeling, this DESCRIPTIVE PSYCHOLOGY 71 change in the method of observation would be less easily observable. The exclusive employment of the inner sense as a source of experience led eventually to a purely introspective psy- chology, a form which has in most recent times developed in close connection with the problems of explanatory psy- chology. A common distinction made by the psychology of the inner sense is that between outer and inner experience, with the demand that the methods of investigation in the two spheres should be correspondingly different. Modern psychology tends, however, to emphasize the unity of experience, the difference between mediate and immediate depending mainly upon the point of view adopted . 1 The history of psychology did not, however, start with these contrasts. The point of departure consisted rather in a phase of the problem of inner perception, the problem, namely, how it is possible to have a consciousness of one’s own perceptual activities. It is not the difference among the phenomena, like feelings, emotions, decisions, etc., on the one side, and colors, tones, etc., on the other, but the fact that in the perception of colors, tones, etc., we have also a consciousness of these perceptions that led to the assumption of a special inner sense. The inner per- ception, in the pregnant sense of the term, whose object is itself an ordinary perceptual process, appears to us as a special form of inner experience, as a turning inward (to remain within the same circle of ideas) of the inner sense itself. But, as happens so often in the history of psychol- ogy, it was the most striking phenomenon, which need not by any means be the simplest, which became a starting- point for psychological investigation. A second point of view originated in the older doctrine of inner sense from the mistaken distinction between sense- 1 Cf. Chapter V, 3 (6). 72 HISTORY OF PSYCHOLOGY perception and its reproductions, reproductions which were called memory if they recurred in their original connections, and imagination if they were fantastically combined. It was the outer sense which was active in sense-perception, the inner, in memory and imagination. This external point of view became prominent particularly in connection with faculty psychology. A second and higher stage of psychological reflection than that of the older psychology of inner sense arose when the totality of mental phenomena was conceived as a closed sys- tem of experience accessible only to the inner sense, and when the latter was regarded as an independent source of experience. The merit of having taken this step belongs to John Locke. The connection of psychology with epistemo- logical questions finally led, in the second half of the cen- tury, to a branch of psychology which in a peculiar manner formed the basis of a descriptive or phenomenological psy- chology of the inner sense. The expression “inner sense” is one of the oldest of Ger- man philosophical terms. As old a writer as Notker (d. 1022), who, following the version of Boethius, was the first to translate the writings of Aristotle into German, translated sensus by “uzero sin” and imaginatio, ratio, and intelli- gentia by “innero sin.” The term inner experience {inner e Erfahrung) is of much later origin, occurring as Erfahrenheit in the works of the mystic Weigel in the sixteenth century. (a) The Older Doctrine of the Inner Sense Scattered observations on the peculiar nature of inner per- ception are found early in the history of psychological reflec- tion. Plato referred to a cognition of cognition, a knowledge of knowledge. He also held that for true pleasure the So£a aXrjOgs of it was necessary. But he did not continue DESCRIPTIVE PSYCHOLOGY 73 this addition of one psychical act to another, because it led, as he thought, to an infinite regress. It was Aristotle who recognized the true nature of the problem of inner percep- tion and who had the good fortune, in dealing with the prob- lem, to make his beginning at a much more tangible point. After discussing the activity of outer perception he raises the question by what activity we become aware of the act of perception itself as distinguished from the objects per- ceived. There can be no special sense for the perception of the act of perception, according to Aristotle, as that would necessitate another sense for the perception of the first. Accordingly, all the senses must have in common the power to perceive themselves, a power which Aristotle calls the npcorov aiaOijpiov. Since this power also perceives the common attributes of the different sensory contents, it is also called the common sense ( Gemeinsinn , kolvt) aiad Tjcrt?). It is noteworthy that Aristotle does not make the distinction between inner and outer sense at all. He rather avoids the assumption of an inner sense co-ordinate with the outer and adheres to the purely conceptual dis- tinction according to which a common faculty of sensation merely shows differing modes of activity. The concept of consciousness, which we see Aristotle approaching here, is not actually developed by him in the present connection. He does not approach it until later, in his description of the attributes of the Supreme Being, in the Metaphysics . 1 Within the Peripatetic school Strato saw in the conscious- ness of the contents of sense-perception a result of an activ- ity which was from the outset separated from perception. In a peculiar way Alexander of Aphrodisias returned from this to the older conception, employing the term avvalaQ^m^ for the consciousness of perception, a notion which was des- tined to remain of central importance in the Neo-Platonic 1 Cf. Chapter VI, 1 (a), below. 74 HISTORY OF PSYCHOLOGY psychology. The Aristotelian doctrine of a common sense, however, shared the fate of many of the other conceptual distinctions of Aristotle, and was interpreted pictorially as an inner sense, sensus interior, which was soon split up, as in the case of the faculty psychology. Galen, for example, distinguished three kinds of inner sense, corresponding to the main groups of phenomena which are its objects, namely, imagination, thought, and memory (to cpavraaTucov, to BiavoTjTiKov f to fxvrj ^ovucov) , thus illustrating the second point of view referred to above . 1 For many centuries hereafter the inner sense is reckoned among the other mental faculties, losing its own distinctive significance more and more in the process. In keeping with the terminology of Neo-Platonism and with the sensus in- terioris hominis, as Augustine called it, Scotus Erigena in the Scholastic period contrasted the inner to the whole group of outer senses. Its analogy to the five external senses is emphasized still more by Avicenna, who has five inner senses — sensus communis, vis imaginativa, vis cestimativa, memo- ria, and phantasm — which are, like their external counter- parts, variously localized. The opposition between outer and inner senses recurs in Thomas Aquinas. The senses themselves cannot become aware of their own activities. The activities of the outer senses are rather perceived by a sense different from them, an inner sense, the sensus communis. This sense, too, is, like its corresponding object, physical. It can, accordingly, not perceive its own activity, and we thus have left one uncon- scious mental activity within the sphere of sense. The doc- trine of the inner sense assumes a peculiar relation, more- over, to that of “ intentional ” or “ mental ” existence. The notion of psychical immanence ( Einwohnung ) is found as early as Aristotle in the doctrine that the perceived object 1 See pp. 71-2. DESCRIPTIVE PSYCHOLOGY 75 exists as such in the perceiver and that the object thought of exists in the reflective intelligence. The history of phi- losophy records this confusion between mental existence and actual existence. Philo’s theory of ideas is founded on the notion, while Saint Anselm developed it into his proof for the existence of God. Thomas Aquinas teaches that the thing thought of is “intentional” in the thought. Consciousness of this thought is rendered possible on account of the incorpo- real character of the understanding, through the reflection of the activities upon themselves. Meanwhile, Saint Thomas denies to the understanding a plurality of simultaneous thoughts, holding that such plurality is possible only as tem- poral succession. The perception of thought, therefore, fol- lows the thought itself in point of time. Thomas Aquinas thus exposes some of the difficulties in the accepted doc- trine of inner perception, difficulties which have reappeared in modern psychology. That the introspection of a mental process immediately follows the latter is a view of inner perception held by many modern psychologists. This central problem of inner perception was subsequently lost sight of again. The treatments of the number and clas- sification of the inner senses in the psychological systems of the Reformation period are far removed from the actual facts of consciousness. Here again the inner sense plays its part mainly in connection with the reproductive processes. Imagination and memory play the leading roles. Associated with them, occasionally, is the old common sense. Distinct from these attempts at classification is the view of Amerbach who interprets the inner sense in Aristotelian fashion as the common sense, treating it as a necessary presupposition to the activity of the outer senses. The physiological interests of the time reflect themselves in the attempts to explain the activity of the inner sense by reference to the movements of “nerve spirits” in the brain, as, for example, in Casmann, 76 HISTORY OF PSYCHOLOGY who well characterized inner perception as actus refledus or as iterata cognitio. The Cartesian definition of the soul as a thinking substance represented inner perception as be- longing to the essence of the soul. The solution of the prob- lem thus suggested was, however, not turned to account by Descartes for the advance of empirical psychology. He rather placed the outer and the inner senses side by side, thus preparing the way for the sensualistic psychology of a later day, in the sense, for example, of Hobbes, who called the discrimination of sensations itself a sensation. (6) The Inner Sense as an Independent Source of Experience The classical expression of the doctrine of the inner sense is found in John Locke. Locke based his Essay Concerning Human Understanding upon the simple fact that all our ideas originate either in sense-perception or in reflection, by which the soul becomes aware of its own activities. Thus introspection is recognized by the side of sense-perception as an independent source of knowledge. The traditional analogy between the outer and inner senses is thus strictly subordinated. It is true that reflection always presupposes sense-perception; at the same time Locke, supported by Cartesian metaphysics, asserts the independence of inner experience. - The epistemological consequences of this doctrine were drawn by the English sensualists Berkeley and Hume, in both of whom the Lockian antithesis continued. Berkeley found the object of reflection, of “inward feeling,” as he called it, in one’s own existence, without, however, admitting the idea of spirit or self. The subject of the various psy- chical activities enumerated — willing, ideation, etc. — cannot be grasped by reflection, although the latter can direct itself upon these activities themselves. The result is a consider- DESCRIPTIVE PSYCHOLOGY 77 able restriction of the scope of inner perception, which, for the rest, corresponds with Berkeley’s conception of the soul . 1 Over against Locke’s distinction between sense and reflec- tion Hume placed his own antithesis of impressions and ideas. We now have impressions of introspection standing parallel to impressions of sense-perception. The latter orig- inate within the soul, from unknown causes, whereas the former originate for the most part from our ideas. Thus the intellectualism which is the usual accompaniment of the psychology of inner perception asserts itself in Hume’s psychology also. Locke’s distinction between sensation and reflection per- sisted in English psychology. It received a variety of in- terpretations in French sensualism. Condillac disputed the validity of reflection as an independent source of knowledge. It originates, rather, in the specific direction of the atten- tion toward ourselves, which, of course, presupposes imagi- nation and memory. This significant reference to the power of attention is meanwhile weakened by invoking another kind of consciousness, in addition to reflection, which is di- rected upon separate ideas. Neither can we attach much importance to the physiological explanation of the inner sense offered by Bonnet, who ascribed it to the power of the soul to set soul fibres in motion spontaneously. Locke’s doctrine of the inner sense received its most im- portant transformation through Leibniz’s celebrated distinc- tion between perception and apperception. In perception the soul merely contains ideas, in apperception it becomes conscious of them. As a knowledge of the soul of its inner states, the Leibnizian apperception bears a fairly close re- semblance to Locke’s reflection. Leibniz’s distinction de- rives a greater significance, however, for the development of the concept of consciousness in so far as it was later to 1 Cf. p. 27. 78 HISTORY OF PSYCHOLOGY become identified with the distinction between unconscious and conscious states of the soul. 1 While Wolff repeats the Leibnizian distinctions with un- diminished emphasis in the later phases of the period of En- lightenment, the traditional doctrine of the inner sense re- appears, as in Baumgarten, who gives a complicated account of external and inner sensibility. Among the eclectic repre- sentatives of the “Popular Psychology,” Meiners bases his doctrine of the inner sense upon the methodological principle that the number of separate organs must be determined upon the basis of the diversity of inner experience. The most interesting development of the doctrine of inner sense in this period is due to Tetens. Since psychical processes are per- ceived through the inner sense in the same manner as physi- cal are perceived through the outer senses, he opines that we perceive nothing but phenomena in both cases. The two arguments for the objectivity of the external world prevalent in the theory of knowledge dominant at the time, namely, (1) that sensation, as confused perception, does not repro- duce the simplicity of the outer world, and (2) that percep- tion depends upon the condition of the sense-organ, are ex- tended by Tetens to inner perception also. Every psychical process may be composed of heterogeneous elements, which have the appearance of simplicity only for our apprehen- sion, and for inner observation the brain is the organ upon which it depends. For this reason mere introspection can never reach the elements of psychical life. These can be reached only by thought, which operates by analysis similar to that employed by natural science in the study of white light, which to observation appears simple in character. These consequences follow with a certain necessity when the doctrine of inner sense is really taken seriously, but they stand in sharp contradiction to psychological experience in 1 Cf. Chapter VI, 2. DESCRIPTIVE PSYCHOLOGY 79 which, in contradiction to physical, the elements are given concretely . 1 The inner sense assumed a many-sided significance through the psychology of Kant. Kant distinguished the inner sense from apperception. The experiences of the inner sense run their course in time, and yield phenomena, as do the outer senses. Apperception, on the other hand, relates to the pure ego, the subject of all thought activities. As object, meanwhile, of inner experience, the ego knows itself only as it appears. This view of the activity of the inner sense, which grows out of Kant’s theory of knowledge, con- tinues in Kant’s empirical psychology, as set forth in his Anthropologie, in a close parallelism between the inner sense and the outer senses. Kant further distinguishes between the inner sense ( sensus interims), as a mere cognitive faculty, and the inward sense ( inwendiger Sinn, sensus interior), the feeling of pleasantness and unpleasantness, thus denying the original relation of the inner sense to the totality of inner experience . 2 A more exact definition limits the inner sense to passive psychical states. It is not pure apperception, as this belongs only to the faculty of thought; it is a conscious- ness of that which affects it in so far as it is affected by its own play of thought. As perception it is in this sense also subject to illusions, as when one, for example, mistakes per- ceptions of the inner sense for external phenomena. Here we obviously have a reappearance of the older idea that the objects of the inner sense are the processes of memory and imagination. The heart of the Kantian doctrine consists in the idea that the inner sense substitutes for the pure or transcendental ego the empirical ego with its variety of con- scious phenomena. This curious duplication of the ego re- curs frequently in subsequent philosophy. 1 On the concept of psychical element, see below, Chapter VII, 3. 2 Anthropologie in pragmatischer Hinsicht, 1798, § 13. 80 HISTORY OF PSYCHOLOGY The Kantian doctrine of the inner sense was severely criti- cised by Herbart, who urged that, as a faculty of introspec- tion, the inner sense would require some superior faculty in its turn, and so forth, without end. Still, the positive ex- planation of Herbart’s, according to which one mass of ideas observes another, is still more seriously burdened with in- ner impossibilities, if possible, than the theory which he criticises. Schulze controverted the assumption of an inner sense with different arguments in his Psychologische Anthropologie (1819). The analogy between the outer senses and the in- ner sense is untenable for the reason that the knowledge of a perception as one’s own implies a judgment which cannot be ascribed to the activity of sense. The interposition of a special faculty between the soul and perception in the form of an inner sense can be defended by no arguments whatso- ever. If, in spite of this criticism, certain representatives of sensualistic psychology still occasionally maintain the strict analogy of the inner to the external senses, as is done by Biunde in his Versuch einer systematischen Behandlung der Psychologie (1831) and by Lelut in his Physiologie de la pensee (1862), we may treat these utterances as the echoes, merely, of a theory which at this time and in this form has long been obsolete. The merging of the old problem of inner sense in the more general problem of consciousness occurred partly in connec- tion with the description which the Philosophy of Identity gave of the dialectical development of consciousness. One of the most characteristic attempts to make this develop- ment of consciousness intelligible as a psychological process was made by Ulrici, who held that inner perception was identical with the beginning of consciousness, and derived both from the distinction, originally unconscious, between the self and sensation. DESCRIPTIVE PSYCHOLOGY 81 But it was not in these more or less speculative efforts that the doctrine of inner sense came into contact with the most modern tendencies of descriptive psychology. The question which came into the foreground was the more gen- eral question as to whether pure introspection, which had been transmitted historically in the form of the inner sense, could form the basis of an empirical psychology. At first these efforts of empirical psychology lagged decidedly in spite of the expositions, so opulent in impressions, of Beneke. Fortlage, in his System der Psychologie als empirischer Wis- senschaft aus der Beobachtung des inneren Sinnes (1855), as- serted that the observation of the inner sense was the funda- mental source of experience in psychology. He held that the task of psychology was to construct an empirical science of the human mind founded upon observation within the realm of the inner sense, and to arrive, by induction, at the ultimate concepts of instinct and reason. 1 But in the actual construction of this science the realm of “observation” be- came a mere jostling place of arbitrary assertions. After laborious expositions of the functions of the inner sense, to which are mainly ascribed the attributes of the external senses, the author begins his “observations,” a term which, however, is here merely a synonym for inventive imagina- tion. As F. A. Lange aptly remarks, it would be difficult to find in the two stout volumes a single genuine observation. The sterility of such observations by means of the inner sense demanded its criticism as a source of knowledge. Comte had already made a very searching and influential criticism of it, in which, however, he had identified observa- tion with perception. In his Cours de Philosophie positive (1830-42), he declared every form of psychology claiming to discover the fundamental laws of the human mind to be illusory as long as it relied upon introspection. In spite of 1 System, der Psychologie , Vorrede, X. 82 HISTORY OF PSYCHOLOGY the fact that J. S. Mill, in his account of Comte, undertook to defend perception of psychical phenomena by means of direct memory, it was in England where Comte’s doctrine made the greatest advance. Maudsley, too, in his Physi- ology and Pathology of Mind (1867), rejects self-conscious- ness as a source of psychological knowledge. In Germany F. A. Lange was particularly aggressive in his criticism of inner perception, maintaining that there existed no clear line of demarcation between outer and inner perception. The experience of color in imagery, for example, is regarded as due to the observation of the inner sense. Neverthe- less, there is no essential difference between that and the actual sight of color. Helpless as was the psychology of inner sense against such criticisms, no result was reached regarding the significance of introspection in psychology. In the most recent developments the question has been considered from other points of view, in connection with ex- perimental investigation, where the controversy has centred around the competency of self-observation when regulated by experiment. 1 The doctrine of inner sense underwent a new development through its connection with certain epistemological problems raised by the question of the epistemological significance of the facts of inner perception. (c) The Relation of Inner Sense to Epistemological Problems 2 The connecting-link between the theory of knowledge and the doctrine of inner perception was the problem of “evi- dent” or immediately certain perception. With the ex- ternal, illusory perception was contrasted inner, evident perception. Uberweg, in his Logik (1865), ascribed to inner 1 Cf. below, pp. 136 /. * Cf. with this Brentano, Psychologie vom emp. Standpunkte, p. 101. DESCRIPTIVE PSYCHOLOGY 83 perception the characteristic of material truth, and made this identity of being and knowledge the point of departure for his theory of knowledge. The psychological investiga- tion of the difference between external and inner perception was thus demanded by the theory of perception. In addi- tion to this, empirical psychology had an interest of its own in attempting to establish its right to be regarded as a spe- cial science, through the discovery of a realm of phenomena peculiar to it. Whether this standpoint is made necessary by the nature of psychical phenomena need not be decided here. In any case, the attempt is made solely on the basis of the facts of inner perception. The close relation to epistemological problems is further shown by the fact that it was not regarded as feasible to employ a principle of division derived from epistemological presuppositions. For it was psychology which, as the funda- mental philosophical discipline, was to lay the foundation for epistemological distinctions. The classification of percep- tions introduced by Locke, which presupposed the contrast of mind and body as something given, was accordingly in- sufficient for the more rigid demands. In contrast with these epistemological determinations, there was a demand for a classification of perception on the basis of purely de- scriptive characteristics. The Cartesian doubt, which stands at the threshold of the critical theory of knowledge, prom- ised to be fruitful for the solution of this task. Without any presupposition regarding the nature of psychical events, it illustrated the character of “evidence” or certainty at- taching to any given experience. Inner perception is neces- sarily “evident,” while many experiences derived from ex- ternal perception render the ascription of this characteristic to external perception impossible. Sir William Hamilton utilized this insight for the determination of the sphere of psychical phenomena, characterizing consciousness as im- 84 HISTORY OF PSYCHOLOGY mediate or intuitive knowledge, and emphasizing as a pe- culiar feature of psychical phenomena that they can be re- ceived only in the inner consciousness. The significance of this definition, which appears at first sight as a reversal of the natural determination of the act in accordance with the object, lies just in this ascription to inner perception of the character of certainty or evidence. An attempt to sharpen the distinction between inner and outer perception to the utmost was made by Franz Bren- tano . 1 Upon the descriptive distinction between inner and outer perception he based a similar distinction between the two corresponding classes of phenomena. Psychical phe- nomena are accordingly such as can be perceived only by introspection, while physical phenomena are accessible only through external perception. Brentano thus carried through the descriptive classification of all phenomena into physical and psychical, without having to depend upon transcendental conceptions . 2 The psychology of the inner sense had long employed the assumption that physical phenomena are due to the action of objects upon the mind, while psychical phenomena have their origin in the perception of the activi- ties of the mind. Psychical objects are now defined as the sole objects of inner perception. Brentano names still an- other characteristic of psychical phenomena, their inten- tional or mental “in-existence.” Every psychical phenom- enon refers to an object. In presentation something is presented, in judgment something affirmed or denied, etc. We have a repetition here, in a greatly refined form, of the Scholastic doctrine of “intentional” acts . 3 Indeed, psychical phenomena are for Brentano identical with the acts. The resulting classification contradicts the delimita- tion of the psychical realm given in the treatment of sen- 1 Op. cit., pp. 131 ff. 2 See Chapter V, 3 ( b ), below. 3 See p. 74, above. DESCRIPTIVE PSYCHOLOGY 85 sation and idea. Brentano regards only the acts of sen- sation and ideation as psychical phenomena. The things sensed or represented — a color, odor, or figure — are physical phenomena. The psychology based upon this distinction has recently been called act psychology. According to Brentano, each of these acts is accompanied by a con- sciousness of itself. Every act, accordingly, has two ob- jects. The primary one is the intentional content, the tone, for example, in audition; the secondary one is the act itself as a psychical phenomenon, in this case as the phenomenon of audition. Inner perception thus accompanies every act and is conscious of it in a threefold way: it ideates it, recognizes it, and feels it. These three kinds of inner per- ception also represent the most general classification of psychical phenomena. The teachings of Brentano, which were understood by many to represent a species of Neo-Scholasticism in psy- chology, have been subject to much controversy. They have received their most adequate criticism at the hands of Husserl, who at the same time dealt most successfully with several of the problems of a purely phenomenological analy- sis . 1 Husserl maintains the epistemological identity of inner and outer perception. It is true that there exists the dis- tinction between evident and non-evident perception, but this distinction does not coincide with the distinction be- tween inner and outer perception. An example of the non- evident character of inner perception is the perception of the ego as the empirical personality. Neither can the ma- jority of psychical states localized in the body be perceived as evident, according to Husserl. The source of Brentano’s errors lies in the equivocal use of the term phenomenon. By the phenomenon Brentano sometimes means the objects and attributes which appear, sometimes the experiences consti- 1 Logische Untersuchungen, vol. II, 1901, pp. 7QZJJ. 86 HISTORY OF PSYCHOLOGY tuting the activity of appearing (occasionally contents in the shape of sensations), and, finally, all experiences as such. We thus have a cross classification of experiences, as, e. g., activities and non-activities, and of phenomenological ob- jects, as, e. g., those which belong to self-consciousness and those which do not, that is, psychical and physical objects. He treats, that is, the latter as a classification of experiences into activities and non-activities, and furthermore identifies the contents sensed with the phenomenal characteristics of external objects, so that a general classification of phenome- nological objects results. This criticism is directed toward one of the last offshoots of the doctrine of the inner sense, and illustrates the keenness of the purely phenomenological method of investigation which has been attained in present- day psychology. CHAPTER IV EXPLANATORY PSYCHOLOGY If we were to arrange the tendencies of psychology which have grown up around the problems of explanatory psychol- ogy in the chronological order in which the characteristic tools of these tendencies became known, we should have to put in the first place the observations regarding the uniformities in the more elementary psychic processes. In sense-percep- tions, in memory, in impulsive and instinctive activities uni- formities were observed even before the day of experimental investigation, which must have suggested strongly the idea of the uniform connection among psychical phenomena. The most important notion available for explanatory pur- poses was that of association. Association psychology ter- minated in the conception of psychology as a mechanics of ideas. A second point of departure consisted in the exten- sion of psychological investigation beyond the border of in- dividual psychology. The resulting science of comparative psychology was helped forward especially by the notion of development or evolution. Rut, more than anything else, it was contact with the natural sciences, during the century just passed, which furnished explanatory psychology with new tools and opened new paths which led to the discovery of those psychic laws which are the goal of association psy- chology. i. Association Psychology Explanatory psychology has been said to supplement de- scriptive psychology in the respect that it investigates the dispositional characteristics of mental life in addition to its 87 88 HISTORY OF PSYCHOLOGY t phenomenological aspect. Although the field of explanatory \ psychology does not coincide with the doctrine of psychical \ dispositions, still the reference to dispositions constitutes one I of the main forms of explanatory psychology, particularly of association psychology. But before the doctrine of associa- I tion developed into a definite psychological tendency, the / concept of association was not only elaborated but the I notion of a mechanics of ideas had already appeared. The I fitful beginnings of association psychology illustrate how fre- quently the continuity of psychological investigation has been broken. For a long period only the processes of association connected with memory were taken into account. It was only gradually that the far broader field of psychical con- nections, in which the concept of association was so long to dominate, was opened. (a) The Early Beginnings of Association Psychology ,The earliest attempts to give an account of the most easily deserved memory functions are made by hylozoism . 1 Par- menides of Elea accounted for memory and obliviscence as he accounted for all the rest of the phenomena of nature, by the mixture of cold and heat. Every idea presupposes a certain combination of these qualities, the idea disappearing when the combination no longer obtains. With no less dependence upon the half-mythical, half-metaphysical psy- chology of the time, Diogenes of Apollonia asserts as the cause of forgetting the obstacle which the body offers to the distribution of air, a belief based upon the observation that one breathes more freely when recollection has been success- ful. Aside from these beginnings, which in any case take 1 Cf. with the following: Bergemann, “ Gedachtnistheoretische Unter- suchungen und mnemotechnische Spielereien im Altertum,” Arch. f. Gesch. d. Phil., VIII, 1895, pp. 336 ff. EXPLANATORY PSYCHOLOGY 89 into account only the negative aspect of memory, namely obliviscence, the first attempt to construct a genuine theory of memory was made by Plato. Plato distinguishes the con- cepts avdfivrjaK from The former signifies the act of reproduction of previous impressions, the latter the pas- sive persistence of ideas due to sense-perception . 1 ’Avdfj.vrjcn'; is the higher faculty. It manifests itself only when the soul in the knowledge of its ideas remembers the impressions of a previous existence. on the other hand, is the capacity of the soul associated with the body to retain impressions of sense-perception. It is said to resem- ble a piece of wax, varying in size according to the individu- ality of different persons, becoming harder and softer, pure or defiled, etc . 2 Aristotle was still more successful in his treatment of the phenomena of memory, dreaming, and the processes of asso- ciation and reproduction. He takes into consideration not only the actual contents but the dispositional as well. His De Anima treats the phenomenology of mental life, the re- maining psychological treatises (the so-called Parva Natu- ralia ) dealing with the dispositional basis. Memory (fj-vrifir]), as the faculty of psychophysical retention, is distinguished from recall ( dvaiuiAvrja/ceadcu ), which is made possible through the association of ideas. As the inner movements which run their course in a series of perceptions repeat themselves, the corresponding memory picture is called up. The principle of association is either similarity, contrast, or temporal succession («<£’ o/iolov rj ivavriov rj tov crvve yyu?). These laws hold not only for single ideas, but for series of ideas as well, only in the latter case they sometimes lose their simple character . 3 For the derivation of these laws of association, which have since become so celebrated, Aris- 1 Phoedo, 73 B ff.; Philebus, 34 B. 2 Thecetetus, 191, C ff. 3 De Mem., 2. 90 HISTORY OF PSYCHOLOGY totle falls back upon the supposed movements of memory- pictures in the blood. These are partly identical or similar, partly simultaneous or immediately successive. Now, the soul has the power to originate, through the agency of the heart, a movement of the blood which can revive the traces of previous impressions in the sense-organ. In addition to this physiological mechanics of associative memory, we find the beginnings of a general mechanics of ideas, at least as far as sense-perceptions are concerned. The stronger movement overcomes the weaker. A number of simultaneous sensations from a single sense-organ are impossible, as such sensations coalesce. Sensations from different sense-organs, however, do not coalesce. The fusion depends upon the fact that the soul can in a single movement sense the similar more readily than the dissimilar. And since every kind of sensation im- plies a specific kind of movement in the central organ, the simultaneous perception of opposite qualities would necessi- tate simultaneous opposite movements. Hence the simul- taneous occurrence of different sensations is manifestly im- possible. All this is distinctly suggestive of the modern attempts to construct a mechanics of ideas, illustrating how Aristotle’s anticipations extend into the most recent times. While English psychology has been dominated by his laws of association, Herbart revived his principles of psychical mechanics . 1 Ancient psychology did not, indeed, develop the Aristote- lian tradition. Incidentally, Maximus of Tyre 2 enumerates the different types of association. The following sentence is ascribed to him: “As a motion imparted to one end of a cord traverses the whole length of the cord, so the reason re- quires only a slight impulse in order to recall whole trains of ideas .” 3 1 Cf. Siebeck, Quaestiones duae de phil. Grcec., 1872. 2 Diss., 16, 7. 3 Siebeck, Gesch. d. Psychologie, II, p. 310. EXPLANATORY PSYCHOLOGY 91 Plotinus, too, mentions the fundamental idea of immedi- ate reproduction, but describes memory merely as a power of the soul. Sense-perception is received into the (pavraarL- kov, where the images are stored. The higher soul then selects from the memories thus stored up in the lower soul. The literature on mnemotechnics, which is rich in content, is distinct testimony to the interest in the practical uses of memory characteristic of the time. When one remembers that up to the time of Augustus no public speaker would dare to appear in public with even the scantiest notes, the interest in mnemotechnical devices is easily intelligible. The beginnings of mnemotechnics, w T hose discovery is as- cribed to the poet Simonides, are legendary, as is the case with similar arts. Most of the precepts along this line about the time of Cicero advise the use of visual pictures as aids to memory. In order to have at one’s command large masses of ideas, they must be localized, say, in a given city, and within the city, in the different buildings, chambers, etc. The theoretical gains from this sort of thing for psy- chology were small, as might have been expected. In Scholasticism the psychology of memory was reduced to the singular assumption that the species of things are pre- served by the soul. It is in this sense that Avicenna defined virtus conservativa et memorialis. More important are the views of John Buridan, which form a connecting-link between the older forms of psychical mechanics and association psy- chology. Although still largely dominated by the concep- tions of faculty psychology, he is convinced of the unity of mental life. The principle of psychical mechanics under- lying his description of the freedom of the will has caused him to be called the Herbartian among the Scholastics . 1 For a long time knowledge of associative connections was confined to the phenomenon of memory. The law of im- 1 Cf. Chapter XII, 2 (a). 92 HISTORY OF PSYCHOLOGY mediate reproduction alone was not lost to empirical psy- chology. As a rule, the formulation was that of Vives: “Quae simul sunt a phantasia comprehensa, si alterutrum occurrat, solet secum alterum reprsesentare.” It was re- served for English psychology of the eighteenth century to place the facts of association in the foreground and to re- gard it as the fundamental form of psychical connections. (b) The Dominance of the Concept of Association The involuntary association of ideas already played an important role in the English psychologists of the seven- teenth century, Thomas Hobbes and John Locke. It was Locke, indeed, who introduced the term association of ideas to designate the process in question. Malebranche, too, was acquainted with the facts of association, which he explained by the simultaneous occurrence of ideas in consciousness. Not until Hume and Hartley, however, in the middle of the eighteenth century, was the concept of association made the central concept of explanatory psychology. In the Treatise of Human Nature (1739-40), Hume enu- merates three factors which can give rise to association : sim- ilarity, immediate spatial and temporal connection, and cause and effect; and in his Dissertation on the Passions (1770) he defines association generally as the principle of facilitated transition from one idea to another. In accordance with the principles of combination of simple ideas arise those complex ideas “which are the common subjects of our thoughts and reasoning”: relations, modes, and substances. While Hume based his theory of association upon psychological experience, he utilized it for his empirical theory of knowledge, one of the main features of which is his bold reduction of the con- sciousness of reality to associatively conditioned relations. As is well known, Hume explains the different kinds of belief, EXPLANATORY PSYCHOLOGY 93 particularly the belief in the reality of the external world, by the force and vivacity of the corresponding idea. In conse- quence of the principle of association, the force and vivacity which belong to a given impression communicate themselves to those related to it. In addition to the reality of sense-per- ception, there is also the reality of ideas of memory, which are distinguished from ideas of fancy by the necessary connections existing among the different perceptions, and, finally, the reality of judgment . 1 Thus, in virtue of the prin- ciple of associative connections, the various kinds of con- sciousness of reality are reduced to the same ultimate fact of consciousness. The connection with the theory of knowl- edge has stimulated an interest in the psychological inves- tigation of the consciousness of reality which has been un- interrupted, and the modern Neo-Humeanism, which finds an ally in psychologism, occasionally approaches again the Humean solution of the problem. Falling in with the ideas of the time, Hartley connected the doctrine of association with the hypothesis of nerve vi- bration and attempted to establish a psychophysical theory of association. He even tried to represent brain changes pictorially, thus returning to the older point of view of the school of Malebranche, a representative of which, Theodore van Craanen, had made graphic representations of material ideas . 2 We are here reminded of the teachings of Descartes, who had described ideas rerum materialium as brain impres- sions produced by movements within the body which are sensed by the soul in perception. Hartley also has capital analyses here and there of complex mental processes, which employ distinctly the fundamental principles of association psychology according to which complex phenomena are ex- plained by the association of their component elements. In 1 Treatise of Human Nature, bk. I, part III, sects. VIII and IX. 2 Tractalus de homine, London, 1689. 94 HISTORY OF PSYCHOLOGY this sense he analyzed the process of speech, for example, into four component parts: auditory impressions, move- ments of the vocal organs, visual impressions of the writ- ten characters, and, finally, movements of the hand in writing . 1 The physiological hypotheses of Hartley were further util- ized by Charles Bonnet , 2 who, in his efforts to exhibit the physiological conditions of mental life, abandoned himself wholly to the speculations of the “nerve-fibre psychology .” 3 Testimony to the many-sided psychological interests of this writer is his fondness for the study of bee life, which has ever been a puzzling problem for psychology . 4 Bonnet’s theory of association can be summed up as follows: Nerve- fibres excited simultaneously or in immediate succession, and those which are spatially contiguous, are connected in such a manner that a repeated motion of any fibre gives rise to a sympathetic movement in fibres connected with it. Even remembered ideas owe their origin to specific move- ments of fibres. The impression, however, made upon the soul by fibres excited for the first time is different from that produced by subsequent excitations. Hence the difference between imagery and sense-perception. Thus the old doc- trine of material ideas, which has passed through a whole series of metamorphoses, reappears again. Traces of the doctrine are also seen in the recent assumption of memory cells in Meynert and Ziehen. In Germany the influence of the doctrine of association is seen partly in the Wolffian school, partly in the recent at- tempts to treat psychological problems in relation to nerve physiology and the physiology of the senses. Like the nat- 1 Observations on Man, his Frame, his Duties, his Expectations, 1749. 2 Essai analytique sur les facultes de I’dme, 1760. 3 Cf. Speck, “Bonnets Einwirkung auf die deutsche Psychologie des vorigen Jahrhunderts,” Archiv f. Gesch. d. Phil., X, 1897, pp. 504 ff. 4 Bonnet, CEuvres d’histoire naturelle, 1779-83. EXPLANATORY PSYCHOLOGY 95 ural sciences, it found support in the growing interest in pathological phenomena. It shared with faculty psychology and the psychology of the inner sense the results of that pe- culiar species of introspection to which the psychological periodicals of the second half of the eighteenth century, now mostly forgotten, bear instructive testimony. Once the thought was grasped that so important a mental process as association could be explained by the mechanism of the nervous system, it was an easy step to extend this method to the whole field of mental phenomena. The ten- dency found a response in the psychophysical materialism of the French Enlightenment. Thus arose a physiological psy- chology which sometimes tended to approach pure material- ism, sometimes recognized the independence of the realm of inner sense, but sought to bring its phenomena into rela- tion with physiological processes. M. Hissmann aided in the dissemination of this tendency through his translation of Hartley, published in his own periodical (1778 ff.). In his Psychologische Versuche he makes the dependence of mental phenomena upon the brain his starting-point. The nervous system and the brain are conscious, just as other bodies are electric or magnetic. It behooves the psychologist, there- fore, to give attention to physiology, and especially to the anatomy of the brain. To the two general laws of associa- tion, the laws of coexistence and of similarity, he added the law of the physical relation of the inner organs. Certain groups of ideas are to be explained by the natural relations of their corresponding bodily organs. A significant applica- tion of these points of view to the theory of knowledge was made by J. C. Lossius, 1 who attempted to construct a mechanics of the thought processes. Thoughts are composed of sensations: they become truths by a process of comparison with other thoughts, which, in turn, depend upon brain 1 Physische Ursachen des Wahren, 1775. 96 HISTORY OF PSYCHOLOGY movements. Truth as distinguished from contradiction is, therefore, to be explained by harmonious vibrations of nerve- fibres. Lossius thus approaches the form of empirical the- ory of knowledge which developed in the nineteenth century under the name of psychologism. The law of contradiction, for example, would be explained by him as follows : “ Our in- ability to conceive simultaneously a triangle and a quad- rangle is due to the fact that the movements of different nerve-fibres inhibit each other.” It is only necessary to substitute psychical thought processes for the hypothetical nerve vibrations with which Lossius operates in order to get a pretty close approximation to the point of view of psy- chologism, as developed since the time of John Stuart Mill . 1 A mediating point of view was taken by K. F. von Irwing , 2 who maintained that the physiological basis of sensations and of their connections was to be found in the connections among nerve-fibres within the brain. The human mind is distinguished from the animal mind, which is wholly depen- dent upon this structural basis, by the possession of self- active understanding. Irwing is more original in his criti- cism of Bonnet’s naively pictorial theory of memory, and he occasionally has good observations in his more purely de- scriptive passages, as in his comparison of previously experi- enced secondary ideas with present ones. The most important psychologist of this group is E. Platt- ner , 3 whose treatment of sense-perception is particularly de- tailed. To the external impression of the peripheral nerve- endings is added an inner impression in the “nerve spirits” of the brain. It is not until attention is turned upon this that the understanding recognizes ideas. The preservation of ideas he originally conceived after the fashion of the per- sistence of material ideas, later attributing it to facilitation 1 Cf. Chapter V, 3 (a), below. 2 Erfahrungen und Untersuchungen iiber den Menschen, 1778. 3 PhUosophische Aphorismen, 1776-82. EXPLANATORY PSYCHOLOGY 97 of nervous action. The combinations of the ideas of im- agination are accounted for by the participation of active thought, as well as of the laws of association. Another tendency of the day sought to interpret the facts of association in a purely psychological manner. Marcus Herz, who was acquainted with Kant through correspon- dence, not only outlined 1 a theory of association but also sug- gested a general mechanics of ideas. True to the intellectu- alism of his time, he viewed the activity of the ego as a form of ideation. Each idea has a focal point of greatest vivacity. A definite interval always elapses between the complete ap- prehension of an idea and the direction of the attention to its successor. The length of the interval depends partly upon the structural content of the separate ideas, partly upon their mutual relation, i. e., their identity or similarity, difference or contrast, etc. The law of association, however, is not a pri- mary law. It rather depends upon the law that the repe- tition of an activity occurs with minimized effort and hence with a lessened interval. A matter deserving of special recognition is his vigorous denial of the doctrine of the unin- terrupted presence of ideas. His concept of facilitation ap- proximates to some extent the modern notion of psychical disposition. It is true that J. D. Iloffbauer’s Grundriss der Erfahrungs- lehre (1794) is still based upon the old principles of faculty psychology and the psychology of the inner sense. Never- theless, all the objects of the inner sense are shown to be subject to the law of association by the fact that the re- producing and the reproduced ideas are already connected within a single total idea. Against such a unitary law of association and its derivation from the concept of imagina- tion L. H. Jakob contended in his Grundriss der Erfahrungs- seelenlehre (1791), a work distinguished for its clear, 1 Versuch uber den Schwindel, 1791. 98 HISTORY OF PSYCHOLOGY methodical formulations. In spite of many interesting re- marks on the conditions of sensation, its dependence upon the receptivity of the sense-organs, and the like, we find many concessions to the old faculty psychology . 1 The one work of this period which has been most successful in escaping general oblivion is the Versuch iiber die Einbil- dungskraft, by G. E. Maass, who represents a transition be- tween the empirical psychology of the eighteenth century and the idealistic psychology of Romanticism. The defi- nition which he offers of imagination as that active faculty of the soul which compares the parts of a complex object shows the influence of the great thinker who dominated all his contemporaries. Imagination underlies the law of asso- ciation both in its three well-known forms and in its fourth form, the law of revival, which states that among “ a number of ideas the most prominent idea is revived.” Prominence here is determined by clearness. Maass thus suggests the point of view, common to many of his contemporaries, of psychical mechanics, a form developed particularly during the nineteenth century. In this versatile period of the Enlightenment we find also the first attempts to apply the law of association to aesthetics, attempts based upon the significance of association for the affective life, with which writers had long been acquainted. As a famous historical illustration of the recognition of the associative connections between sensations and feelings may be cited the curious edict issued in Paris forbidding the play- ing of the Alpine cowherd’s melody so long as Swiss mer- cenaries served in the French army, on the ground that it produced homesickness . 2 The principle of association which 1 Cf. the particularly happy description of these efforts in M. Dessoir, op. cit., pp. 232 ff. 2 Homesickness ( Heimweh ) is the translation of nostalgia. The physician J. J. Scheuchzer published a work, De nostalgia Helvetiorum, in 1731. EXPLANATORY PSYCHOLOGY 99 Fechner introduced into aesthetics is partly anticipated in Henry Home in the form of the law that the pleasantness of a given object tends to spread to other objects . 1 The tra- ditional principle of unity within variety is also explained by association. The succession of ideas which must occur at a certain rate presupposes a corresponding interchange among the ideas, which is partly facilitated by association, partly restricted to a determinate set of relationships. The prin- cipal function of association thus consists in binding to- gether the greatest possible number of ideas into the clos- est possible relationship. A similar theory of association is formed in Diderot. His definition of the beautiful, “Beau est tout ce qui reveille en nous l’idee des rapports,” seems to have been formed with the principle of association in mind. The fusion of both tendencies is seen in the aesthetics of Herder, in which association also plays an important role. The psychological formulation of aesthetic problems appears in clearer form in his older studies and sketches on Plastik, and in the torso of his fourth Kritische Waldchen, than in his earlier and more polemical Kalligone. The variety of indi- vidual taste as well as the mutual influence of the experience gained from the various senses, seen most conspicuously in the senses of sight and touch, everywhere emphasizes the significance of association. It is true that the prob- lem of the relation of form and content was derived from the rationalistic aesthetics of Baumgarten. Nevertheless, the harmony of form and content shown in the aesthetic object is for Herder a fact which has definite psychological conditions ; it is a special result of association. Herder anticipates mod- ern aesthetics in still another way. If the spirit of a work 1 Elements of Criticism, 1762, p. 66. Cf. A. Tumarkin, “Das Associa- tionsprinzip in der Geschichte der Asthetik,” Arch. f. Gesch. d. Phil., XII, 1899, p. 257. 100 HISTORY OF PSYCHOLOGY of art and of its forms is to make its appeal, it must be through an act of sympathy, an inner affinity, in virtue of which we can transport ourselves into these forms, and thus simulate their psychic life . 1 Elsewhere he writes that we can appreciate the human form because we ourselves live a bodily life, and can thus share the life of the spirit which the body reveals . 2 We have here an anticipation of Lotze’s symbolic beauty, in so far as aesthetic products appear to us as symbols of psychic states experienced by ourselves. These reflections, finally, suggest the notion of empathy (Einfiihlung) , a conception derived from the philosophy of Romanticism, which has become a concept of fundamental importance in aesthetics through the discussions of Lipps. Association psychology shared the fate of many other in- tellectual tendencies of the eighteenth century in being obscured by the philosophical movement originated by Kant and developing into the philosophy of Romanticism. By the side of the mighty problems which emerged in this movement, the problem of the theory of knowledge, the prob- lem of development in nature and history, the attempts of the psychology of the Enlightenment to add to the store of human knowledge, often motived, as they were, by prac- tical interests, must have lost their significance. Associa- tion psychology was perhaps more successful in surviving the attacks of the Critical Philosophy and the storm of Ro- manticism. The tradition was continued in England, the home of associationism, occasionally even throwing off the influence of intellectualism, as in the case of Brown , 3 who extended the processes of association to the realm of the feelings. Brown further sought to unify the laws of associa- tion, and his assumption that a principle of unity was to be 1 Plastik, and the accompanying studies, VIII, pp. 56/., 91, 153/. 2 Kalligone, 1800, XXII, p. 173. 3 Lectures on the Philosophy of the Human Mind , 1820. EXPLANATORY PSYCHOLOGY 101 found in the coexistence of ideas with a common feeling again shows the significance of the feelings for the processes of association. Among the Scottish philosophers Sir Wil- liam Hamilton, although still under the influence of faculty psychology, gave a description of the association processes, which he treated as an illustration of the law of redintegra- tion, the law that ideas which have formed parts of a sys- tem tend to recall each other. In closer connection with English empiricism of the eighteenth century, the funda- mental outlines of associationism were drawn by James Mill (1773-1836), who ranks as one of the most important of the founders of the new association psychology. The only class of psychical facts recognized by Mill is sensation, the only law recognized is the law of association, of which association by contiguity is the most general form. Associationism owes its traditional logical formulation to John Stuart Mill, who announced, in his System of Logic (1843), a psychological law which was to serve as a universal explanation of the connection among states of conscious- ness. 1 The main classes of states of consciousness are thoughts, feelings, will-acts, and sensations. The classifi- cation is indeed unsatisfactory enough. What is important is the claim that it is the laws according to which states of consciousness succeed each other which form the proper subject-matter of scientific psychology. The usual laws of association are cited as illustrations of the process in ques- tion, and they are given a fictitious significance by their sug- gested analogy to the law of gravitation. An example of such a general law is the law that any psychical impression, no matter what its cause, will reappear in a similar though weakened form when the original cause is no longer present. Mill thus calls attention for the first time to the so-called symbolic function of memory images, which has been treated 1 Bk. VI, Chap. IV. 102 HISTORY OF PSYCHOLOGY by a number of modern psychologists, H. Cornelius, for ex- ample, as an ultimate and inexplicable fact of consciousness. The attempt to unify the doctrine of association eventu- ally left standing only two fundamental forms of the process: inner association, for which similarity and contrast are the two most important qualitative characteristics of the con- tents associated, and outer association, which results from the empirical connections of these contents within conscious- ness. The demand for unification was also met by Alex- ander Bain, from whose first important psychological work, The Senses and the Intellect (1855), dates an increasing in- terest in the association theory. He reduced the various forms of association to association by similarity and contigu- ity, a contrast which resembles that between inner and outer association. Aside from these simple forms of association, there are also complex forms, and, within the realm of im- agination, so-called constructive associations. The rigid scheme of association is thus expanded so as to include all forms of psychical phenomena from the most simple mental connection to voluntary actions. If the law of self-preser- vation is added, you can take even a voluntary action and reduce it completely to associations between spontaneous actions and the chance agency of pleasure. The tendency toward the unification of the associative processes has recently given rise to the singular controversy over the question whether in the last resort association by similarity or association by contiguity is to be regarded as the primary form. In the discussion between Hoffding and Lehmann one of the most instructive examples was the association, Alexander the Great- Frederick the Great, which Hoffding ascribed to similarity between the two generals, while Lehmann 1 regarded the case as one of association by contiguity due to the common predicate, “the great.” 1 Wundt, Phil. Studien, V, pp. 96 ff.; VII, pp. 169 ff VIII, pp. 86 ff. EXPLANATORY PSYCHOLOGY 103 The measure of truth in both positions well illustrates the futility of the whole question. The whole theory of association was thought out to its ultimate consequences by Herbert Spencer. His elements of psychical life or “units of feeling” are psychical atoms constituting an unknowable spiritual substance. The con- nections among these simple contents of consciousness are formed in accordance with the fundamental laws of associa- tion that every “feeling” as well as every relation between “feelings” associates itself with its like in the past experi- ence of the individual. There is evidently a close relation between this process and the physiological processes of ha- bituation, and Spencer thus returns, in a sense, only in a greater measure, to the physiological point of view of Hart- ley. But Spencer belongs to a new epoch. His psychol- ogy is based upon the notion of development or evolution and thus connects itself with the more recent tendencies of psychology in Germany. Psychology was not directly influenced by the ideas of Romanticism so much as were the other mental sciences. Its development rather occurred in connection with the thinker who, alone among his idealistic contemporaries, sought to found the science of psychology anew — I mean Herbart. In his hands psychology becomes a science, striving to express psychical uniformities by the aid of an exact scientific terminology. Going far beyond the facts and forms of association, he seeks to restate these in terms of a science of psychical mechanics. 2. Psychology as a Mechanics of Ideas At the time of Herbart German psychology had lost itself in the ideas of Romanticism. The most important psycho- logical idea of the time, if we abstract from the metaphysical / I 104 HISTORY OF PSYCHOLOGY background, was the construction of the history of conscious- ness out of the concept and the fundamental facts of con- sciousness . 1 Herbart himself is, perhaps, more representa- tive of his time than he is often thought to be, since he based his psychology largely upon metaphysics. In his observa- tions on the history of psychology he discussed the relation of his own point of view with those of a number of his prede- cessors and his contemporaries . 2 He defends the rational I psychology of Leibniz against the attacks of Kant. He I asserts his own point of departure to be the psychology of I Fichte, whose merit it was to expose the contradictions in- volved in the concept of the ego. Among his contemporaries Fries had, according to Herbart, most conclusively proved the shortcoming of the Kantian psychology, while Weiss \ had based psychology upon a dynamic conception of nature. \ The metaphysical presuppositions upon which he founded his own psychology assigned him a position from which he never advanced. He is left standing at the beginning of the nineteenth century much as Leibniz was left standing at the beginning of the preceding one . 3 Nevertheless, it is the merit of Herbart to have introduced into explanatory psychology the concept of a mechanics of ideas based upon the valuable conception of psychical uniformity. The soul which, on account of the unity of consciousness, must be thought of as a simple, real being, contains, as forms of its self-preservation, presentations or ideas. Similar or dis- parate ideas fuse with one another; opposite or partially opposite ideas inhibit one another in proportion to their opposition. Inhibition has the effect of diminishing the intensity of ideas. The relations involved in the process of inhibition, moreover, are amenable to exact mathemati- cal treatment. As a “statics of ideas” mathematical psy- 1 Cf. p. 29. 2 Werke, Hartenstein ed., V, pp. 251 ff. 3 Cf. p. 27. EXPLANATORY PSYCHOLOGY 105 ckology seeks to ascertain the terminal condition in which ideas are in equilibrium; as a mechanics of ideas it seeks to determine their intensities during their course. A statics of ideas takes as its point of departure reflections such as the following: If we start with two opposite ideas of equal intensity, the intensity of each will, in consequence of the resulting inhibition, be diminished to one half of its original intensity. The inhibition sum is in this case equal to the total inhibition which distributes itself over the two ideas. In the case of the unequal intensity of the two ideas, a and b (a > b), it is sufficient that a quantity, b, be inhibited in both. Now an inhibition sum, b, will distribute itself over both ideas in such a manner that each will suffer in- hibition the less, the greater the force which it possesses. J ) 2 dJ) The inhibition of a will therefore be ; of b, . By cl -f- b ci -f- b simple subtraction the intensity of the remaining ideas can be determined. 1 But Herbart has still not arrived at the fact of the threshold of consciousness. The condition under which an idea would entirely disappear below the threshold of consciousness would be & < ~. = 0, whence b=0. Only off- o when three ideas, a, b, c (a>b> c), occur can the weakest disappear below the threshold, under the auxiliary assump- tion that the inhibition sum is now b + c. The fundamental equation for the mechanics of ideas is also derived from a consideration of the inhibition sum. 2 In their original state ideas are entirely uninhibited and constitute an inhibition sum. As the inhibition sum di- minishes, the movement of ideas begins. If the inhibition sum is S, and stands for receptivity, and if within a time, t, a quantity, z, of presentation is pro- duced, then the receptivity at the expiration of t is only (f> — z. If the force of a disturbance, say, a brightness, is /3, we have the equation /3(—z)dt = dz, whence z = 4>(l —er pt ). To this equation corresponds, in addition to the general principles of metaphysics, the known fact “ that, first, every perception requires a short interval of time if the resulting idea is to attain to a finite degree of strength among other ideas; secondly, that a perception prolonged beyond a cer- tain time produces no increase in the resulting strength of the idea.” The passage clearly suggests the problem con- nected with the increase of the sensation stimulus with which subsequent sense psychology was to occupy itself, and, indeed, the ascending curves obtained by empirical measurements occasionally approach the fundamental form deduced by Herbart. Up to a certain point, too, mathe- matical psychology connected itself again with the Her- bartian problem of the statics of ideas in subjecting the prob- 1 Op. cit., § 94 . EXPLANATORY PSYCHOLOGY 107 lems of the distribution of degree of clearness in conscious- ness, and of the inhibition or assimilative interaction of ideas, to experiment. Nevertheless, the passages in Herbart’s psychology in which he shows signs of abandoning his imaginary mechanics of ideas for actual psychological ex- perience are of rare occurrence. Indeed, it is merely a frac- tion of this experience, a limited range of certain intellectual processes, with which his psychology deals. Following out his presuppositions to their logical conclusions, Herbart intellectualized mental life to a degree nowhere else reached in the history of psychology. The Herbartian tradition was continued by a small number of disciples for a number of decades. One of the most im- portant of these, M. W. Drobisch, projected an ambitious programme for psychology, claiming for it an insight into the true nature of reality beyond that of any other science . 1 In the contents of consciousness, in the variety of our idea- tional, affective, and desiderative life, we observe the inner processes themselves which constitute spiritual life. The first task of psychology is the entire exclusion of meta- physics and the creation of an empirical psychology which should be really worthy of the name. A related prob- lem is the formulation of a mathematical theory of mental life. A third problem consists in the application of the results obtained to epistemological and metaphysical ques- tions. It is in the first of these attempts that the influence of natural science, for which the exact spirit of Herbartian psychology has such a deep affinity, makes itself most def- initely felt. The man who contributed most in this direc- tion was Theodor Waitz , 2 who abandoned the Herbartian scheme and regarded psychology as one of the natural 1 Empirische Psychologie nach naturmssenschaftlicher Methode, 1842, 2d ed., 1898, Einl., pp. 9 ff. 2 Lehrbuch der Psychologie als Naturwissenschaft, 1849. 108 HISTORY OF PSYCHOLOGY sciences. The Herbartian tradition was maintained more strictly by W. F. Volkmann, who made a conspicuous attempt to prove the services of realism in the realm of psychology. An intermediate tendency is represented by Hermann Lotze, the most independent of the group of psychologists who usher in the most recent development of psychology. He sought to formulate a physiology of mind but maintained, at the same time, that the results must be interpreted in the light of general psychological conceptions, and this for the reason that he had long ago ascertained secretly, by statistical methods, that the average life of the great posi- tive discoveries of exact physiology had been four years! It is true that Herbart had admitted the existence of phys- iological conditions of mental states. The significance of the body for states of consciousness is proved by the influ- ence upon them which the body exerts, by the bodily res- onance observable in connection with certain psychical states, and by the co-operation of the body in the produc- tion of volitional acts. Lotze, however, was the first to take account of the physiological conditions of mental life in any thoroughgoing or extensive way . 1 He did not con- tent himself, for example, with simply placing sensation and feeling side by side, as two elements of mental life, but analyzed the genesis of simple sensation itself into a series of distinguishable stages. In the first place, the external stimulus is transformed into the excitation of the sense- organ; this, in turn, produces the nervous process which is eventually to result in sensation, and, finally, we have the problematic modifications within the brain itself. Here the process emerges from the physical , realm. The impres- sion which the excitations within the nervous system pro- 1 Cf. with this the historical retrospect by Kiilpe, Grundriss der Psy- chology, 1893, p. 27. [English translation, p. 26. Trs.] EXPLANATORY PSYCHOLOGY 109 duce in the soul might, in the first instance, be an uncon- scious process, which is then succeeded, as a sixth member of our series, by a simple sensation. As a seventh stage might be mentioned attention, which conscious sensations receive in greater or less degree. With distinctions such as these, derived from the modern physiology of the senses, are combined ideas reminiscent of the Herbartian mechanics of ideas, which lead to a number of general propositions concerning the relation of impressions in the soul, as follows: 1 (1) If two impressions which are qualitatively the same en- ter consciousness, the result is a simple sensation of double the strength of each taken separately. (2) If two impres- sions are qualitatively dissimilar, but are at the same time comparable, it depends upon the mental excitation in which they are produced whether they fuse or not. Two colors, for example, if not separated spatially, must fuse. (3) If a number of different nerve-fibres receive an equal amount of the same stimulus, and if the impressions really sum them- selves, the intensity of the resulting sensation will be propor- tional to the sum of the nerve-fibres through which it is excited. (4) If a stimulus of a constant amount is dis- tributed among a number of nerve-fibres, the resulting sen- sation is much weaker than if the total stimulus is carried by a single nerve-fibre. (5) Disparate stimuli, like colors or tones, do not result in an intermediate sensation, but only in a distribution of attention. It is remarkable how many psychological problems are affected by the foregoing generalizations. In connection with the first of these propositions, renewed attempts have been made at an elementary construction of sensation. The second suggests presuppositions which were to serve as the starting-points for some purely psychological theories of space. Taken in conjunction with the fifth, it also suggests 1 Meiicinische P$ych*l*§i», 1|52, 99 . 23# ff. 110 HISTORY OF PSYCHOLOGY the phenomena of mental rivalry. The third and fourth propositions, finally, are attempts to bring into relation the intensity of sensation and the retinal distribution of the stimulus, a question which was later taken up again by Fechner. In the discussion of the complex functions the moral point of view characteristic of Lotze’s thought occasionally comes into the foreground. He applies the law of persis- tence, which it is so tempting to invoke in support of the retention of memory images in the brain, to the soul itself. The difficulty of understanding how an infinite number of impressions can persist in one substance is no greater in the case of the soul than in the case of the brain. The soul hypothesis, however, satisfies our moral needs more ade- quately than the other. Lotze accordingly proceeds upon the assumption that memory as well as miscellaneous recog- nition and the course of ideas are conceivable without the co-operation of the brain. 1 Lotze’s psychology here issues in a pure spiritualism, in which the rigor of psychological analysis is combined with a disposition to yield to moral interests and needs. 2 Among those who have helped to preserve the funda- mental idea of Herbart’s psychical mechanics is Lipps. Although he shows a closer affiliation with the views of Her- bart in his first principal work, Grundtatsachen des Seelenle- bens (1883), than in his subsequent publications, neverthe- less, the aim which underlies all his work is to bring the realm of psychical processes under the reign of necessary law. If one were asked to state the principal difference between the psychology of Herbart and that of Lipps, it might be said to consist in the attempt of Lipps to substitute for the mechanism of conscious psychic processes, such as Herbart contemplated, the mechanism of unconscious psychic proc- 1 Op. cit., p. 473. 2 Cf. above, p. 30. EXPLANATORY PSYCHOLOGY 111 esses, which was to serve as the conceptual basis for the explanation of the phenomena of consciousness. To the Herbartian school is also due the first stimulus to the development of ethnic psychology, which has become one of the most important branches of comparative psy- chology. 3. Comparative Psychology The term comparative psychology might be said to include those branches of psychology which go beyond the realm of phenomena given in individual self-observation and which depend in the main upon the method of comparison. Ethnic psychology and, in large part, animal psychology come under this classification. The influence of Darwinism which is noticeable in the treatment of a number of special prob- lems is felt mainly in this field. As a special branch of comparative psychology may also be mentioned individual j psychology, in so far as it attempts to separate individual / from general psychical phenomena by the aid of compara- / tive methods. (a) Ethnic Psychology The science of ethnic psychology is usually said to have\ been founded by Steinthal and Lazarus, who issued their Zeitschrift fur Volkerpsychologie in I860. As we look back to those early beginnings from the point of view of the con- cepts of ethnic psychology originated in recent times by Wundt, the psychical mechanics of Herbart seems the most inappropriate point of departure possible for the considera- tion of this group of phenomena, particularly since the in- vestigators referred to, in spite of the wide scope of their programme, regarded ethnic psychology merely as a field for 112 HISTORY OF PSYCHOLOGY the application of the principles of psychical mechanics. Nevertheless, the general character of the Herbartian specu- lation was not without aid to these investigators. 1 A thinker trained in the abstractions of the Herbartian system, which dealt only with the general relations obtaining among mu- tually inhibitive intensive magnitudes, would readily substi- tute for the latter corresponding factors when these mani- fested themselves in human society. The beginnings of ethnic psychology in England were in- dependent of these efforts and were dominated by different conceptions. It was English empirical psychology that was the first to enter the broad field of ethnological phenomena for the purpose of utilizing these phenomena for psycho- logical purposes. The investigations of prehistoric man and the beginnings of civilization by Lubbock and Tylor (1865) opened the way. But it was the psychology of Herbert Spencer, based upon the evolutionary idea, which was bound to transcend the standpoint and to overstep the limits of a merely individual psychology. In spite, however, of the wealth of ethnological data displayed in these and similar works, they tended after all to run to philosophy of history rather than to remain pure ethnic psychology. ) These modern developments were anticipated early in the eighteenth century by G. B. Vico (1668-1744), 2 who simi- larly combined problems of the philosophy of history with reflections in ethnic psychology for his interpretation of the historic process as a process conditioned by psychological laws. It is true that, in so far as he confined himself to a comparison of the life of peoples separated from each other in space and time, his method was merely a method of his- torical induction; nevertheless, the subjects investigated by 1 See Wundt, Volkerpsychologie, I, 2d ed., 1904, Einl., pp. 18 ff. 2 In his work, Sdenza nuova d’intorno alia commune natura delle na- zioni (1730). EXPLANATORY PSYCHOLOGY 113 him — language, myth, custom, and laws — belong without question to ethnic psychology. ( b ) Animal Psychology 1 The contention of Descartes that animals were soulless automata, a conception popular at the time, was not seri- ously controverted until the eighteenth century. Condillac ascribed to animals a soul life essentially resembling that of man . 2 There are, according to him, no specific differences between man and the animals as regards mental constitu- tion, the difference consisting merely in the greater range of man’s experiences. The narrow range of an animal’s experi- ence is due to its low physical development, and particularly to the comparatively low development of its sense-organs. The influence of sensualism, which tends to correlate the range of experience and knowledge with the development of sense-organs, is clearly evident here. Condillac’s position was controverted by H. S. Reimarus , 3 one of the early cham- pions of deism in Germany. The instincts of animals are not acquirements due to intelligence and experience but are purely congenital traits. As the bearer of ideals and possessor of intelligence and free will, man, compared with the lower, animals, is simply a higher order of being. In his analysis of the animal mind Reimarus accordingly confines himself to the determination of these congenital instincts. He finds ten classes of these, and the adaptations which they severally show furnish him with arguments for the wisdom of the Creator. The influence of the semitheological doctrines of Reima- rus upon natural scientists was practically negligible. His 1 Cf. with the following E. Rddl, Geschichte der biologischen Theorien, II, 1909, pp. 427#., 214#. 2 Traite des animaux, Amsterdam, 1755. 3 Allgemeine Betracht. u. d. Triebe d. Tiere, 1760. 114 HISTORY OF PSYCHOLOGY view of instinct, however, was revived in the nineteenth cen- tury in the form of a certain conception growing out of the German philosophy of nature. Starting with the phenom- ena of the simplest instinctive activities, Fichte had ar- rived at the notion of the subject as pure activity. For Schelling the animal instincts were the significant activities of the same power which reveals itself most profoundly in art. The metaphysical will of Schopenhauer, too, nowhere reveals itself more immediately than in instinct, and Hart- mann bases his conception of the unconscious, which is of such central importance in his system, largely upon the doc- trine of instinct. One of the best evidences of the reflex in- fluence of these general philosophical ideas upon psychology are the writings of the physician C. G. Carus , 1 which seek to portray, often by the aid of myth and allegory, the grad- ual growth of consciousness in the animal world. Man and the lower animals are bound together by many analogies. Observation gives place to admiration of the hidden essence which comes to expression, e. g., in the profound symbolism of the spiral line of the snail; by unbridled analogies the author lifts himself into the realm of metaphysics and of those spiritualistic ideas with which we have already become acquainted . 2 Natural science, meanwhile, in its more exact forms, took its starting-point from Condillac. Lamarck was prominent among those who developed the notion of evolution which was suggested by Condillac. He enriched the current doc- trine by the important addition of the idea that the results of the experiences gained during the life of the individual do not disappear at the death of the individual but are trans- mitted to the offspring by heredity. The views of the psy- 1 Psychologie oder Geschichte der Seele in der Reihenfolge der Tierwelt, 1866. 2 See above, p. 30. EXPLANATORY PSYCHOLOGY 115 chical life of animals held by Darwin were somewhat naive, since he ascribed to animals a soul life essentially similar to man’s but existing in a somewhat masked or undeveloped form. Instinct is to be explained as inherited habit, and the differences among instincts are to be accounted for by reference to the same process of natural selection by which we explain differences of bodily structure. Since Wundt’s studies in animal psychology , 1 this branch has become more closely affiliated with general psychology. A singular revival of long-forgotten ideas which carry one back to Scholasticism is found in Erich Wasmann . 2 He agrees with Reimarus in separating instinct entirely from intelli- gence. Intelligent actions differ from instinctive through the presence in the former of the consciousness of end. The absence of the consciousness of end and of the power of abstraction in the lower animals constitute an impassable gulf, according to Wasmann, between man and these lower forms. An effective counter-influence to such views is found in modern experimental animal psychology, which even goes to the opposite extreme, as in Loeb’s theories of the chemical reactions of lower animals . 3 (c) Influence of Darwinism The influence of Darwin upon psychology was also evi- dent in connection with many special problems. Thus we meet with the attempt to explain color sensations from an evolutionary point of view. After the English statesman W. E. Gladstone and L. Geiger had contended that the Greeks— Homer, for example — had not been able to distin- 1 Vorlesungen uber die Menschen- und Tierseele, 1863, 5th ed., 1911. [Engl. tr. ( Human and Animal Psychology) by Creighton and Titchener, New York, 1895. Trs.] 2 Instinct und Intelligenz im Tierreich, 1899. 5 See above, p. 42. HISTORY OF PSYCHOLOGY guish blue from black or gray from green, H. Magnus 1 sought to show that man was originally entirely color- blind. The order of colors in the spectrum from red to violet is claimed to be the order in which human sensitivity to the various color-tones developed; and Magnus does not shrink from the conclusion that sensitivity to ultra-violet light will at some future time be developed. Similarly, new points of view were developed in the study of the origin of language. Darwin’s own views stood mid- way between the theory of imitation and that of instinctive sounds, the two theories which formed the most natural approach to a psychological comprehension of the problem of language. He held that language originated partly in the imitation of natural sounds, partly in the instinctive cries of man himself. Starting from a similar point of view, G. Jager sought to explain the development of human lan- guage from the sounds uttered by animals . 2 He describes in detail the stages which occurred, as he supposed, in the development of expression among animals, from accidental to voluntary utterance, from mere motor discharge to com- munication. The influence of bodily structure, too, is taken into account. Thus quadrupeds, for example, whose chest movements are affected by their mode of locomotion, lack the delicacy in the control of respiratory movements which is requisite for speaking or singing. These biological fan- cies, however, were soon abandoned again, along with vari- ous other speculations, such as the genealogical theories of language of Schleicher, the theory that inarticulate inter- jection formed the substrate out of which articulate lan- guage developed, and the like. Evolutionary psychology also made a number of attempts, which owe their origin to modern biology, to determine the 1 Die geschichtliche Entwicklung des Farbensinnes, 1877. 2 Uber den Ursprung der menschlichen Sprache, 1867 and 1869. EXPLANATORY PSYCHOLOGY 117 elementary psychical attribute of organized matter. We have to do here with the transformation of the problem of determining the psychical element which is co-ordinate with the element of matter, a problem originating in metaphys- ical psychology, or in the border field of empirical psy- chology, into the problem of the kind of psychical activity which characterizes various stages of organic evolution. Hering named memory as the elementary psychic character- istic of organized matter. 1 Racial memory is developed in the evolutionary series as a whole, by heredity. The related distinction between individual and phyletic memory subse- quently found its way into many psychogenetic considera- tions, such as those of W. Preyer. 2 (d) Individual Psychology A last branch of comparative psychology occupies itself with individual differences. If we pass over the secular psychology of the Renaissance, 3 the main ideas of individual psychology are found in that versatile era, the period of the Enlightenment. Herder, in 1778, voiced the demand for a “characteristic” psychology. Oddly, he directed his polemic against the ars charaderistica which had originated in the philosophy of Leibniz and which Ploucquet and Lambert sought to develop into a general science of conceptual signs. Psychology, he urged, should take particular care not to lose itself in such fruitless generalities. Herder recommends as a model for psychologists the physiology of Haller, whose law of muscular sensitivity Herder proclaimed as the fun- damental law of sensation. Spirit-filled, like Pygmalion’s statue, Haller’s physiological treatise is to be raised to the rank of psychology. A year later appeared Feder’s inves- I 1 Uber das Geddchtnis als Funktion der organischen Materie, 1870. 2 Die Seele des Kindes, p. 230. 3 Cf. p. 57, above. 118 HISTORY OF PSYCHOLOGY tigations of the will, in which the idea of special psychol- ogy was also definitely expressed. These various movements and ideas were voiced in the Magazin filr Erfahrungsseelen- lehre, published by C. P. Moritz, founded in 1782. The whole problem of individual psychology, the psychology of individual differences, has come into special prominence in recent years in its connection with the applications of psy- chology, particularly to the field of education. An initial problem here, according to L. W. Stern, is created by the fact that psychology, as an analytic science, which isolates mental processes, stands in fundamental contradiction to all those branches for which the mental life, as an individual whole, i. e., as a personality, is of significance. 1 The fact that the divisions of general and individual psychology, on the one hand, and of pure and applied psychology, on the other, cross each other, leads to one of the most actively controverted questions of contemporary psychology. The various tendencies of comparative psychology which devote themselves to the study of special social groups cannot be followed in detail here. They belong, in any event, mainly to the present. Occasionally we find striking discrepancies between investigations of this sort, which are not always undertaken with purely psychological motives, and exact psychological reflection. Here belong hypotheses like those of Weininger which have achieved an ephemeral reputation, and according to which the specific difference between the sexes is to be explained by reference to the wholly untenable conception of a mental state in which sen- sation and feeling have not yet become differentiated from each other. 2 1 Psychologie der Aussage, Heft I, 1903, p. 15. 8 Weininger, Geschlecht und Character, 7th ed., 1905, pp. 127 /. EXPLANATORY PSYCHOLOGY 119 4ft 4. Influences of Natural Science The last stage in the development of modern psychology is characterized by the influence upon it of natural science. The effect of this influence was not that the tendencies of explanatory psychology which were motived by purely psychological considerations, an account of which we have already given, were supplanted by the modes of thought characteristic of natural science. Rather did the attentive consideration of the methods of science and of the border problems of psychology and science bring the unique char- acter of the problems of psychology into clearer relief. The contact of psychology with natural science was thus manifold. That the idea of the regularity of events, which had lent vitality to science since the Renaissance, also served as an ideal in psychology can be proved by the evidence of centuries . 1 It was in the nineteenth century, however, that the growing knowledge of the central nervous system came to the aid of the older efforts to determine the physiological basis for a definitely outlined system of psychological ideas, thus resulting in the so-called modern science of phrenology. But the method of science, too, found its way into psy- chology. It came from the direction where the problems of science and of psychology find a common meeting ground, that of the physiology of the senses. Here the basis was ; laid upon which experimental psychology as an independent branch of investigation could be founded. (a) The Newer Phrenology Phrenology has a long preliminary history in the various theories regarding the seat of the soul. Only the roles, so to 1 Cf. Chapter VIII, 1, below. HISTORY OF PSYCHOLOGY 120 /-speak, in these two branches, were in a way interchanged. / In the older theories the point of departure was psychology, / which accordingly reacted upon brain physiology; and the l comparatively meagre knowledge of brain anatomy gave \ unrestricted play to the most extravagant hypotheses. The psychological motive which led Descartes to locate the soul in the pineal gland, strange as it appears to us nowadays, dominated psychology for centuries. Since we can have only a single impression of an object at any one time, there must be some place where the separate views from the two eyes, for example, or any other such disparate impressions, are united into a single whole before they enter the soul . 1 The organ in which this fusion takes place must, it is evident, be one which is not duplicated in the brain. The motive, however, which prompted Descartes to decide upon the pin- eal gland was that it was only here that the unification of impressions could be accomplished by means of the ani- mal spirits ( spiritus animates ) which fill the ventricular cavi- ties of the brain. The fundamental idea of Descartes that the coalescence of disparate mental impressions could occur only through their conjunction in some one point of the brain appealed so strongly to the psychologists of the seven- teenth and eighteenth centuries that there was hardly an unpaired structure in the brain which was not at some time or other a candidate for the honor of being the seat of the soul. Lancisi and Bonnet held the seat of the soul to be the corpus callosum, Digby the septum pellucidum, Haller the pons Varolii; Boerhave located it in the medulla oblongata, Plattner in the corpora quadrigemina. /The doctrine of the seat of the soul combined with the faculty psychology which, in comparison with the Cartesian doctrine of the soul as a simple, indivisible substance, already represented considerable analysis, to form the well-known 1 Les passions de I’dme, I, p. 32. EXPLANATORY PSYCHOLOGY 121 system of phrenology of F. J. Gall , 1 a system which illustrates what varied psychological tendencies meet in the psychology of the latter part of the eighteenth century. Gall trans- formed the fundamental concepts of faculty psychology into organs of mind. The origin and connection of mental processes were ascribed to nerve vibrations, to which corre- sponded, on the psychological side, the association of ideas. In addition to various fundamental psychical dispositions or faculties the soul has a number of characteristics, such as intelligence, will, attention, and the like. Each faculty possesses all these attributes. The number of these funda- mental traits is said to correspond to the number of instincts, of which Gall enumerated twenty-seven, such as sex, philo- progenitiveness, friendship, cunning, pride, avarice, and the like. Assuming that each of these faculties was matched by a corresponding brain structure, Gall proceeded to elaborate the practical science of phrenology. Since the brain struc- tures in question are located superficially, the skull would show corresponding conformations which can be easily as- certained by tactual exploration, thus affording an objec- tive means for the ascertainment of mental endowment. Although Gall anticipated many modern conceptions, such as those of congenital tendencies to criminality or the ten- dency of supernormal persons to insanity, his art was com- mercialized and degenerated into charlatanism. The untenability of Gall’s phrenology was proved in the first part of the nineteenth century by the French experi- mental psychologists Magendie and Flourens. Flourens ascribed different function-complexes to the medulla oblon- gata, the corpora quadrigemina, and to the cerebellum and cerebrum. The last vestige of the old question of the seat of the soul is found in his influential doctrine of the vital 1 Gall, Vorlesungen uber die Verrichtungen des Gehirns. Herausge- geben von H. G. C. von Selpert, 1805. 122 HISTORY OF PSYCHOLOGY nodes. The point of the V-formed gray mass at the beak of the so-called calamus scriptorius, with which the fourth ven- tricle passes over into the fissure of the spinal chord, is the seat of life in the sense that its extirpation or injury results in instant death. 1 The psychical functions proper, how- ever, remain localized in the entire area of the cerebral hem- ispheres. The functions in question are intelligence and will, whose localization he conceived of in such wise that the most minute part of the organs involved could act in place of the whole. Intelligence and will, however, are very com- plex functions, and it is difficult to see how they can be localized in the smallest structure of an organ so highly differentiated as the brain. The disposition to take refuge in the older-style phrenology in order to escape from these difficulties was encouraged by the partial confirmation of the theory of Gall through the discovery by Broca, in 1861, of the so-called centre of speech. The advance of modern phrenology, as distinguished from the particular system of Gall, consisted, in the first place, in the substitution for the older organs of mind certain special centres or areas con- nected with certain peripheral functions such as the move- ments of co-ordinated muscle groups. In the second place, the inner senses of Gall were forced to give place to psychi- cal elements, usually sensations and ideas, which the psy- chology of Herbart had brought into prominence. It was ac- cordingly assumed that the cortex contained sensory centres for the reception of incoming stimuli and for the initiation of motor innervations. Each of these centres, in turn, con- tains sensory and idea cells. The latter possess the power of reviving sensations, as the excitement of the sensory cells tends to communicate itself to the idea cells. This was the form of the theory as taught by Meynert and as later applied especially by H. Munk, who gave it consider- able currency among brain physiologists. 1 Rech. exper. sur lesfond. du syst. nerv., 2d ed., 1842, p. 204. EXPLANATORY PSYCHOLOGY 123 Closer to the results of psychological analysis is a second form of phrenology which separates the areas in which the connections among sensations, and probably also their repro- duction and the complex psychical processes, occur from the ideational centres, as special association centres. Thus the psychological services of the association theory fin d recognition in the field of pure psychology. The controversy regarding the association centres psy- chology might well have left to the brain physiologists. Aside from the details mentioned, two results were reached which were of general interest for psychology. In the first place, the question regarding the seat of the soul, which had occupied psychology for centuries, was definitely rendered meaningless by the discovery of the motor areas by Fritsch and Hitzig. In the second place, the results of the study of brain physiology confirmed anew the inconceivable com- plexity of the apparently most simple mental processes. How many components might be contained in a given men- tal process of which no trace appears in consciousness was revealed especially by the study of those cases of brain lesion which resulted in the splitting up of mental factors which ordinarily occur together and the disappearance of a given factor from the original complex . 1 ( b ) The Influence of Sense Physiology \ In spite of the close relationship which existed between \ sense physiology and psychology, owing to their common ' connection with the problem of perception, the results of this relation were for a long time sufficiently meagre. The classical physiologists of the first half of the nineteenth cen- tury were themselves obliged to make acquaintance with the psychological aspect of the sensory functions, and for / / 1 Cf. with this Wundt, Grundzuge der -physiol ogischen Psychologie, I,/ 6th ed., pp. 341 ff. 124 HISTORY OF PSYCHOLOGY this they drew freely upon the philosophy of their time. While psychology generally followed philosophical specula- tion only too readily, it is a remarkable fact that the tran- scendental idealism of Kant influenced psychology only in- directly, through sense physiology. Johann Muller, who is one of the founders of the newer sense physiology, at the early age of twenty defended the thesis, Nemo psychologus nisi physiologus, a principle to which he remained loyal throughout his life . 1 Rejecting Schelling’s philosophy of nature, he returned to the great philosophers of the past, Kant, Spinoza, and, among the younger thinkers, particularly to Herbart. It was especially the Kantian doctrine of space and time as pure intuitions which he incorporated into his theory of perception. In seeking for a physiological sub- strate of these transcendental functions he found the manifestations of this directly in sensation. The retina, for example, feels itself as spatially extended. Not less char- acteristic of Muller’s psychology is the principle of the specific energy of the senses, which likewise points to cer- tain philosophical presuppositions such as are implied in the recognition of the fact that psychical processes, and sensory processes in particular, are incommensurable with the processes of the external world. The conception of the immediate reality and of the incomparable uniqueness of psychical processes may be said to be a common conviction of the epoch in question. In this, too, perhaps, consists the greater historical significance of Muller when compared with, say, Purkinje, who also ranks as one of the founders of modern physiology . 2 Few of his observations, which extend to nearly all branches of biology, bear his name. In psy- chology the greater clearness of light rays of short-wave 1 Cf. Stumpf, “H. v. Helmholtz u. d. neuere Psychologie,” Archiv f. Gesch. d. Phil, VIII, 1895, pp. 303 ff. 2 Purkinje, Beobachtungen und Versuche zur Physiologie der Sinne, 2d ed., 1825. EXPLANATORY PSYCHOLOGY 125 length in dim light is called the Purkinje phenomenon, and even this phenomenon had been known a long time, although it had not been utilized for the theory of vision. There are numerous precepts in the Koran, for example, which are to be carried out at a certain hour of the day, owing to the fact that red and blue threads become invisible in the twilight. It was Muller’s school which was to give to the world the investigator who closed once and for all the gap between physiology and psychology, Helmholtz, who devoted the main strength of his best working years to investigations in physiological and experimental psychology. The two works upon which his fame mainly rests, his Handbuch der pliy- siologischen Optik (1856-66) and his Zur Lehre von den Tonempfindungen (1862), were devoted to the psychology of the senses. A mathematical physicist by natural endow- ment, his principal achievements in the theory of vision and audition are due to his supreme mastery of the math- ematical technique necessary for such investigations. Helm- holtz’s psychological theories, however, have a definite philosophical background, which may be said to be a more profound version of the idealism of Muller, particularly on the epistemological side. Already in his Konigsberg inau- gural address, Tiber die Natur der menschlichen Sinnesem- pfindungen (1852), he expounded the view that sense ex- perience is merely a sign of the existence of some ob- jective quality, never a copy which in some way reproduces its real nature. Sensation as merely a symbol of the external world— this doctrine remained fundamental to his main work and served as an explanation of the structure of the organs of vision. Dining the fifties and sixties of the last century 7 investigation in the field of vision was, indeed, extremely active, as the names of Briicke, Listing, Volkmann, Fech- ner, Donders, Panum, and others will recall, and this serves 126 HISTORY OF PSYCHOLOGY to explain, to some extent, how such a work as Helmholtz’s Physiological Optics could come into existence. Still, the study of it serves only to increase our admiration for the creative energy of its author. The thoroughgoing appli- cation of the experimental method, the criteria which under- lie the analysis of the complex sense-perceptions, the points of view for the derivation of the psychical products from their elements — these achievements have never been lost to psychology. f With the recognition of the psychical activities involved in perceptions a large group of psychological problems admitting of exact treatment came into view, with the re- sult that sense psychology became in a very genuine sense a model for modern experimental psychology. These psy- chical activities were thought by Helmholtz himself to be intellectual activities, an elaboration, logical in its begin- nings and gradually becoming unconscious, of sensation ele- ments into the constituent parts of perceptions. This empir- ical point of view, which stood in sharp opposition to the nativism in sense psychology that had grown out of Muller’s theories, was developed in close dependence upon a philo- sophical writer whose Logic was one of the most influential works of the middle of the nineteenth century, John Stuart Mill. Mill’s empirical logic, which was championed in Ger- many by no less an investigator than Justus Liebig, met with a friendly reception particularly among natural scien- tists. It was not the doctrine of association, however, which Helmholtz borrowed from Mill but rather the doctrine, so much controverted, of unconscious inductive and analogical inference, an idea which he utilized for his own theories of perception. That a natural scientist should go to a logician for light on psychological questions bears witness to a truly remarkable dislocation of the boundary-lines of the sciences. Although Helmholtz was extremely critical of philosophies EXPLANATORY PSYCHOLOGY 127 of nature, declaring his own allegiance to Mill’s inductive method, he himself now and then unwittingly fell into the mode of thinking which he disparaged. The notion of de- velopment or evolution he never adopted. His analysis of the human sensory functions, which, in spite of its empirical character, makes no use of the evolutionary principle, oc- casionally reminds one of the attempts of the philosophies of nature to discover the laws of nature in the activity of human intelligence. The sense physiology of Helmholtz was, of course, intended to be predominantly psychology. But this psychology did not undertake an investigation of the simple psychical processes but assumed certain supposed psychical processes in the complex activities of perception. The eye is for Helmholtz a physical apparatus whose func- tion it is to mediate certain sensation elements, like color, brightness, and so forth. Back of these sensations, how- ever, stands intelligence, which acts upon them like a mental faculty. These conceptions are connected with the attempt, often noticeable in Helmholtz, to dispose of cer- tain psychological problems involved in perception, prob- lems which are not amenable to treatment of the degree of exactitude required by natural science, in the easiest and quickest way possible. In this way Helmholtz sometimes approached perilously near to a popular intellectualism of which psychology subsequently had to free itself. (c) Experimental Psychology The problems which we associate with experimental psy- chology to-day were not clearly defined until very recent times. Most of the beginnings in the transformation of the method of psychology were made by the psychology of the special senses which has just been described. The great physiologist Ernst Heinrich Weber took the idea, which 128 HISTORY OF PSYCHOLOGY had, indeed, been expressed before, namely, that one must test the instruments of sensation just as the physicist and chemist must test the instruments with which they work, and made it the starting-point for purely psychological in- vestigations. He not only applied this test in his own investi- gations of the perceptions of space and of pressure, but he also pointed out the psychological conditions of reliability in comparison, as, for example, of the differences in accuracy in the reception of simultaneous and successive stimuli. By varying the interval between the two stimuli and noting the rate of diminishing accuracy with the increase of the interval he even prepared the way for the investigations of memory by the use of exact methods. “Since the oppor- tunity for exact measurements of mental processes comes so rarely,” he wrote, “I recommend these investigations to the attention of psychologists.” 1 In these noteworthy words we meet with a distinct recognition of the importance of exact experimental investigations. The law which has been for all times associated with the name of Weber was in the first instance merely a result of observation. In his inter- pretation of this fact he recognizes a peculiarity of the comparison of sensations in the fact that here two magni- tudes are not compared with a common standard of mea- sure but directly . 2 Psychology did not at once heed the admirable suggestions of Weber. Attempts like that of Bonatelli 3 remained iso- lated until the new ideas were again vitalized by philosophy. In studying the history of psychology one is frequently surprised at the metaphysical framework which supports psychological systems. Nevertheless, it must not be forgot- ten that many psychological points of view owe their origin 1 Tastsinn und Gemeingefuhl, 1846, p. 546. 2 Op. cit., pp. 560/.; cf. Chapter IX, 1 (6), below. 3 Dell’ Esperimento in Psicologia, Brescia, 1858. EXPLANATORY PSYCHOLOGY 129 to their relation to purely philosophical problems. An illustration of this is Gustav Theodor Fechner, who com- bined the exact investigation of his time in the psychology of the senses with profound and fantastic ideas derived from Schelling’s philosophy of nature. Starting with the prob- lems of the philosophy of nature of Romanticism, which had been obscured by the dominant philosophical tradition and which was kept alive by a few philosophical scientists, Fechner defined psychophysics as the exact science of the relations of body and mind. The idea that body and mind represent the dual manifestations of a fundamentally unitary substance already formed the basis of his Zendavesta, pub- lished in 1851. His problem was to ascertain the functional relation between the two series of phenomena and, in par- ticular, to establish the law according to which the inten- sity of mental activity varies with the variation in the intensity of its underlying physical activity. Later he expounded schematically certain fundamental relations be- tween body and mind and between lower and higher forms of spiritual life by aid of the relation between arithmetical series of lower and higher orders. 1 The scheme of geo- metrical orders led him, by a somewhat uncertain line of thought, to make the relative increase of physical vital energy the measure of the increase of the corresponding psychical energy. 2 With this was connected the idea that the soul would sum these increments, dy, just as the kinetic energy of a body is regarded as the sum of its absolute in- d/3 crements, d/8. Thus the fundamental formula, d^—K-^-, and as its integral the formula of measurement was arrived at. Without any thought of the relation of this formula to Weber’s law, he submitted a paper on the subject to W. Weber in 1850, who was impressed with the correctness and 1 Zendavesta, II, p. 334. 2 Cf. Psychophysik, 1860, II, p. 554. 130 HISTORY OF PSYCHOLOGY keenness of the fundamental idea, although unfortunately it did not agree, as he thought, with the newer discoveries. Fechner at length discovered an empirical foundation in the fundamental psychophysical law for brightnesses, and it was not until after a number of experiments with weights that he discovered the broad basis of empirical facts in the investigations of E. H. Weber. The science of psychophysics, as Fechner conceived it, is to be distinguished from psychology proper as well as from physics, and aims at the exact determination of the relation- ship between psychical and physical processes. It begins with the psychophysics of extra-organic stimuli, which seeks to determine the relation between consciousness and the external world and which serves as an introduction to the psychophysics of the bodily organism. For there is a psy- chophysical activity within the bodily organism which stands intermediate between external stimulus and sensation, and it is the relation of this to the purely psychical activity within that the “inner psychophysics” seeks to determine. To this field are transferred Weber’s law and the phenome- non of the threshold, under the assumption that psychophys- ical activity is proportional to the stimulus. In the further development of these ideas the question of the psychophys- ical continuity and discontinuity comes distinctly into the foreground. The latter arises when the movements of psy- chophysical activity occur below a certain limit called the conscious threshold. The result is a number of psycho- physical steps or stages. As conscious processes which are distinguishable by us are continuous below our principal threshold, so also our own consciousness is a part of a more general, inclusive consciousness. With the loosening of the bond with which Fechner had connected ideas from the philosophy of nature with the problem of the measurement of sensations, the fundamental EXPLANATORY PSYCHOLOGY 131 psychophysical problem admitting of exact treatment which remained was that of the relation between the intensities of sensation and stimulus. The restriction of metric psy- chology to this problem was the more likely to lead to some disappointment since the development of Fechner’s meth- ods, which showed a tendency to approach the quantitative determinations of physics, rendered them more and more useless for the purposes of psychology. 1 At the same time there arose a new group of problems calling for inves- tigation according to the new principles of psychical mea- surement. The course of ideas, the relation as regards clearness of simultaneous contents of consciousness, the processes of recall, which formed, indeed, the original interest of the science of psychical mechanics with its mathemati- cal speculations — all these problems had to be investigated anew by empirical methods as soon as an exact basis for psychological measurement had been discovered. The im- pulse to these investigations was given by certain remark- able differences in temporal estimation which were notice- able in astronomical observations in the employment of the so-called eye and ear methods. The problem here is to estimate the position which a star passing through the telescopic field occupies with reference to the threads of a micrometer at two successive strokes of a second’s clock. 2 In the year 1795 the discrepancy of eight tenths of a second between the findings of the London astronomer Maskelyne and of his assistant Kinnebrook led to the dismissal of the latter. The incident attracted the attention of the noted astronomer Bessel, who recognized the subjective variations in temporal estimation as a fact of general import and studied it somewhat exhaustively under the name of the 1 Cf. Chapter IX, 3, below. 2 Cf. Wirth, Die experimentelle Analyse der Bewusstseinsphenomene, 1908, pp. 305 /. and 393. 132 HISTORY OF PSYCHOLOGY personal equation. He sought a psychological explanation of the phenomena by bringing them into relation with the variability in the temporal succession of the acts of hearing and seeing. 1 Later the phenomena were investigated fur- ther with the aid of artificial visual stimuli. Here belong the studies of Hartmann, 2 who also interested himself in the problem of decimal equations, i. e., of the systematic errors occurring in the estimation of the decimals of a lin- ear element which is not further divided. But even the efforts to exclude these errors through an objective method of registration led to an important psy- chological discovery. Arago, in 1842, employed the stop- watch to record the moment of the passing of a star; later the electrical contact key was generally introduced as a means of registration. The hope was thus entertained of determining the time of stellar passage with perfect accu- racy, a hope which received support from the belief of physiologists of the time that the physiological processes involved in nerve conduction took place with very great rapidity, a rapidity about equal to that of light. Neverthe- less, the objective control by means of recording instruments still showed time differences, which were thereupon inter- preted as reaction times suited to the special conditions of such transit experiments. 3 Time differences of this sort were also studied by Helm- holtz, although from a different point of view. He started with the physiological problem of determining the rate of conduction in the motor nerves of the frog, which he found to be from 30 to 90 metres a second, a rate quite at variance with that assumed by earlier investigators, including Johann Muller. The problem now was to determine the rate of 1 Astronomische Beobacht. d. Sternw. zu Konigsberg, Abt. VIII, 1822, XI and XVIII. 2 Grunerts Archiv /. Math. u. Phys., XXXI, 1858, p. 24. 3 Hirsch, Moleschotts Untersuchungen, IX, 1863, pp. 183 if. EXPLANATORY PSYCHOLOGY 133 nerve conduction in man by means analogous to those em- ployed by astronomers for the study of individual differences. The investigations of Helmholtz on the subject are known to us through his correspondence with his father during the year 1850. A hand movement was to be made as quickly as possible after an electric signal was given. If attention was highly concentrated, the time required was one tenth of a second. Under conditions of fatigue, and if ideation had to intervene before the reaction could occur, the time required was considerably longer, although still regular. Thus the problem of time measurement which was destined to prove so fruitful of results was opened up and was later broadened in its scope by the interpolation of psychical intermediaries by Donders and his pupils. 1 The different tendencies enumerated, the theories of perception of the sense physiologists, the psychophysical speculations of Fechner, and the investigation of the astro- nomical registration errors, all alike pointed to the develop- ment of a new psychology. Wundt treated them as symp- tomatic of a new experimental psychology in his Beitrdge zur Theorie der Sinneswahrnehmungen (1862). He himself penetrated to the very heart of the problem of perception by analyzing perception into its elementary psychical processes, by the aid of the experimental method employed in physiology rather than by the aid of metaphysical specu- lations. In an introductory section on method he under- takes a general justification of the experimental method in psychology. As an illustration of an experiment which has as its object a purely psychical event, Wundt cites the artificial imitation of astronomical observations, whose con- ditions he had himself varied by the introduction of a pen- 1 De Jaager, De physiologische Tija bij psychischen Processen, 1865. F. C. Donders, “ Die Schnelligkeit psychischer Processe,” Arch.f. Anat. u. Physiol., 1868. 134 HISTORY OF PSYCHOLOGY dular movement. The interpretation of the temporal dis- crepancy of one eighth of a second as a psychical constant, which could be either positive or negative, was indeed soon abandoned; nevertheless, the psychological signifi- cance of the fact in question was recognized. As a second example is cited Fechner’s law, which is to be stated in the form of the purely psychological law: “Where two psychical functions stand in immediate dependence upon one another, the dependent function increases proportionately as the logarithm of the one originally variable,” a formulation which later had to be qualified, but which still retains its sig- nificance as an attempt at a purely empirical interpreta- tion of Weber’s law. Wundt’s own contributions confine themselves to the the- ory of sense-perceptions, the problem being to trace the genesis of sense-perceptions from sensation. The main points of the theories expounded in this connection, particularly / that of the relation of certain sense-impressions and mus- \ cular movements, have had to be restated. Other points, \ such as the assumption of unconscious logical processes, 1 have had to be abandoned in view of a more adequate \ knowledge of association processes. 1 This early sketch, however, was only a part of a more general tendency in I the direction of an experimentally grounded science of men- tal phenomena, a science which was destined, as Wundt himself had hoped, to become more than an empty name. With what success the experimental method was extended beyond the field of sense-perception to the more complex ideational processes the monograph of Vierordt, Uber den Zeitsinn (1868), a document instructive even to-day, bears convincing testimony. Aside from some investigations by students of Vierordt, the only experimental work which pre- ceded this was that of Mach. The spirit of the new method 1 Cf. Chapter XI, p. 5 (c), below. EXPLANATORY PSYCHOLOGY 135 is clearly discernible in the problem set by Vierordt to in- vestigate experimentally the various functions and capaci- ties of the time-sense, as these are revealed in the main sense departments, in ideal construction, and, finally, in the purely conceptual apprehension of temporal magnitudes. The con- viction that these were all signs of the beginning of a new era soon gained ground. When Wilhelm Windelband as- sumed his duties as professor of inductive philosophy in Zurich he was ready to say that psychology had definitely freed itself from the shackles of metaphysics . 1 Psychological investigations were yielding a fundamental insight into the elementary constitution of mental life, and the study of the combinations of these elementary processes really constituted the first beginnings of general psychology. These were, of course, as he recognized, merely beginnings. The question why these constant elements combined according to equally constant and incomprehensible laws is referred to a distant future in which a general metaphysical theory of energy would solve at one stroke the most profound problem of both physical and mental phenomena. The life-work of Wundt, who, as we have seen, had early voiced the demand for experimental psychology, extends into our own time. He himself classified the tendencies and the corresponding fields of labor of the new psychology under three general heads . 2 Of these the field of sense-per- ception admits most readily of survey. Here metaphysical and empirical hypotheses 3 have in many cases given way to genetic theories which derive sense-perceptions from the elementary associations between simple sensations. Thus the concept of association, which had during the eighteenth century been wholly confined to memory processes, emerged 1 Tiber den gegenwartigen Stand der psychologischen Forschung, 1876. 2 “Psychologie,” in Die Philosophie im Beginn des XX Jahrhunderts, 2 ed., 1907. 3 Cf. Chapter XI, 3 and 4, below. 136 HISTORY OF PSYCHOLOGY from under the influences of sense psychology with a new significance and scope. In this connection the new principle of original resultants, which asserts that a complex com- posed of psychical elements may be qualitatively new in the sense that it may show features which were not contained in the original elements and which could not be obtained by a mere addition of these elements, came to be recog- nized. Once this fact was verified in the realm of the sim- pler mental processes it was natural to investigate, from the same point of view, the higher and more complex combi- nations, such as the thought processes and imagination. Furthermore, the methods of sense psychology came to serve as models for psychology as a whole. After the experimen- tal method had been introduced into psychology through the influence of sense psychology, the conviction could easily gain strength that introspection was trustworthy only when subjected to experimental control. The simpler mental proc- esses were, in any case, accessible to methodical and sys- tematic introspection, but quite recently, and often in con- scious contrast to the older point of view, the experimental method has been extended far beyond its original field to the most complex cognitive experiences. It is particularly the Wurzburg school whose trust in the reliability of con- trolled introspection led to the disappearance of the earlier and more restricted conception of the scope of the experi- mental method. By the aid of such systematic experimental introspection Ach discovered forms of experience in which a complex con- scious content was present simultaneously as knowledge . 1 Imageless presentation of such a total knowledge content Ach called Beivusstheit, or awareness. Awareness is of two kinds, awareness of meaning and awareness of relation. 1 N. Ach, Uber die WillensUUigkeit und das Denken, 1905, esp. pp. 210 jj. and 235 JJ. EXPLANATORY PSYCHOLOGY 137 Since in the awareness of meaning the felt presence of rela- tions on the basis of excited reproductive processes is of first importance for the presented knowledge, awareness of the second order, like the experiences of surprise, confusion, and doubt, can also be called awarenesses of relation in a narrower sense. In the first case, the question is one of relation to a future factual content; in the last, to a past factual content. The awarenesses of the latter class were already known as independent experiences. We have them in Hoffding’s quality of familiarity {Behanntheitsqualitdt) 1 or in Volkelt’s memorial assurance ( Erinnerungsgewissheit ). 2 The Bewusstseinslage or conscious attitude of Marbe has been interpreted by many as an anticipation of the concept of awareness . 3 Ach expressly distinguished these awarenesses from the phenomena of consciousness commonly known as presentations or ideas. Awareness, or Bewusstheit in Ach’s sense, as simultaneously presented knowledge content, is to be distinguished not only from the highly ambiguous notion of presentation or idea, which is sometimes made to include even the unconscious, but also, and particularly, from image- less ideation. This imageless presentation of knowledge is a psychical experience the existence of which can be demon- strated. Nor is the question one of feelings accompanying ideation: it is possible for an awareness like surprise, for example, to occur without any accompanying feeling tone whatever. The further question whether awareness and feeling are not subdivisions of a common genus is still an open one. The second field for the labors of the new psychology was 1 Hoff ding, “Uber Widererkennen, Association und psychische Ak- tivitat,” Vierteljahrsschrift f. wiss. Phil., XIII, 1889, pp. 420 ff. 2 Zeitschrift fur Phil. u. phil. Kritik, CXVIII, 1901, pp. 1 ff. 3 Marbe, Experimentell-psychologische Untersuchungen uber das Urteil, 1901. Cf. the historical review of theories in Ach, Uber den Willensakt und das Temperament, 1910, p. 18. 138 HISTORY OF PSYCHOLOGY opened up by the investigations of Fechner, and its prob- lems are those which have grown out of the problem of mental measurement. The fundamental insight that psy- chical contents were susceptible to exact quantitative deter- mination was at first handicapped by Fechner’s belief that the stimulus was the measure of sensation, a belief which involved the insurmountable difficulty of bringing two dis- parate realms into quantitative relation. How Fechner’s point of view became transformed into our present point of view is a matter which must be reserved for later discussion . 1 The recognition of the fact that sensations are measurable only as sensations led to a group of purely psychological problems, and the subordination of psychical processes to the concept of collective object opened up to the method of measurement every field of mental life in which quantitative determinations are possible. In a word, Fechner’s psycho- physical methods of measurement were transformed into purely psychical methods of measurement. 'While sense psychology and psychophysics confined them- selves to the investigation of the elementary facts of con- sciousness, the new psychology developed a third tendency which embraced the investigations of the higher processes of consciousness and of their general connections. After psy- chophysics had developed an exact and, at the same time, empirical basis of quantitative determinations for a single group of conscious contents, it was only to be expected that the Herbartian idea of mental mechanics would make its re- appearance. The conviction, however, unmistakably gained ground that a mechanics of elementary associations of the older style was inadequate to explain the actual connection of conscious processes. Every act of will, no matter how simple, every fluctuation in the degree of clearness of con- scious contents, rather pointed anew to the fundamental 1 Cf. Chapter IX, 3 and 4, below. EXPLANATORY PSYCHOLOGY 139 fact of apperception. The Herbartian psychology had sought to reduce this concept, which was introduced into philosophy by Leibniz, to a product of association. Since apperception was viewed as only a special case of the fusion of ideas, its intimate relation to self-consciousness and will was obscured. The examination of the complex processes, however, gave a new significance to this concept, through which the inner activity, immersed as it is in the flow of consciousness, received a scientific expression. And thus experiment was again proved to be an aid to exact investi- gation. 1 Experimental psychology, which owes its birth almost entirely to the German scientific spirit and investigation, soon passed beyond the boundaries of its native country. It has received its most important development outside of Germany in America. Previous to 1880 American books on psychology were written almost exclusively by theologians and educators. While in Germany psychology had long been the battle-ground of competing systems of speculative phi- losophy, Scottish realism held undisputed sway among the older theological writers of America. The earlier writings of Edwards, 2 Hickok, 3 and Porter 4 in the nineteenth cen- tury are typical examples of the species of psychology in vogue. The attempt of Schmucker to introduce into Ameri- can philosophy the conception of psychology as a theory of ideas received little notice. 5 The influences which gave birth to a new psychology in America were twofold 6 and originated in Germany and England, respectively. One was the experimental psychology of Germany which has been 1 See Chapter VI, 4, below. 2 Freedom of the Will, 1754. 3 Hickok, Empirical Psychology, 1834; Rational Psychology, 1848. 1 Porter, The Human Intellect, 1868. 6 S. S. Schmucker, Psychology ; or Elements of a New System of Mental Philosophy, 1844. 6 Cf. J. Mark Baldwin, “Psychology Past and Present,” Psych. Rev., I, 1894, pp. 363 ff. 140 HISTORY OF PSYCHOLOGY discussed in the previous pages. The other was the tra- ditional doctrine of English associationism and Spencer’s notion of evolution or development. To a certain degree, this twofold origin is still commemorated in the controversy between the associationists and the apperceptionists. PART 11 DEVELOPMENT OF THE FUNDAMENTAL CONCEPTS OF PSYCHOLOGY CHAPTER V THE IDEA OF PSYCHOLOGY AS A SCIENCE The history of an empirical science shows not merely a growth of empirical materials but also a transformation, which is not less significant, in the fundamental principles employed in the interpretation of these ma^rials. This transformation is observable even when the alleged self- evidence of the principles in question precludes an histor- ical development. The history of mechanics, for example, shows how so obvious a principle as that of inertia has only comparatively recently supplanted other principles which were seen to be inadequate. But even this principle, to- gether with others which were for a long time accepted as self-evident, has even quite recently been held to be a purely empirical principle which would tend to break down under radically altered conditions, with the introduction of veloci- ties, for example, approximating that of light. The subject- matter, however, of these sciences remains the same; and if one should speak of a change in chemical elements, for example, in virtue of which chemistry would become an historical science in the widest sense, one must remember that the development has been so extremely slow here that it can be practically disregarded in writing the history of chemistry. 141 142 HISTORY OF PSYCHOLOGY The case of the history of philosophy is different. Among the many influences which converge here, one of the most important is that of personal experience. Personal experi- ence, to be sure, plays its part everywhere, but in the philo- sophical sciences we become so uniquely aware of its influ- ence that the history of philosophy can be defined outrightly as a history of philosophical experiences. And these experi- ences have, in the course of time, changed their character. Although the central problems of philosophy can be traced throughout thousands of years of reflective thought, the experiences themselves which give rise to a given philo- ophical problem have become different. Psychology shows both forms of historical development. It deals with experiences as its special subject-matter, but it does so as an empirical science. Here we have to deal, then, with Ganges both in fundamental principles and in the subject-matter itself. In the history of psychology, to be sure, the principles of explanation do not appear with the same clearness as, for example, the principles of explana- tion in mechanics. Nevertheless, it is noticeable that many ideas which are regarded as generally valid by psycholo- gists of to-day were formerly unknown. An example of this would be the notion of the analyzability of complex mental contents into their elements. Of greater difficulty is the question in what sense expe- riences undergo changes, thus producing changes in the subject-matter of psychology. T ist as it is possible for an individual to put himself ba ^ into an earlier period of his life and to recognize it as belonging to himself, with- out actually re-experiencing the emotional excitements and motives in the form of their previous occurrence, so it is possible for a similar difference to exist between the con- scious experiences of people removed from each other by thousands of years. This question need not, however, be PSYCHOLOGY AS A SCIENCE 143 dealt with here, since psychology, in so far as it is not indi- vidual psychology, confines itself to phenomena of general scope and significance. And it is certain that the elements of mental life and the general forms of their combination have undergone little or no change within the historical period. If the physiological characteristics of man have undergone no change within historical times, it is certain that no changes have occurred in the psychological func- tions either. The hypothesis of the color-blindness of the ancient Greeks, for example, has not stood the test of critical examination. There is just as little proof of the assumption that the number of sensation qualities in any sense depart- ment, or that simple reaction-time, or any other essential attribute of such mental processes which can be rendered precise by the aid of psychophysical constants, has under- gone alteration. We do, indeed, find considerable variation in the nomenclature of sensation qualities. Although the discriminable sensation qualities in the higher sense depart- ments were determined with considerable unanimity at an early period in the history of psychology, we find the most diverse opinions concerning those of the lower senses as late as the nineteenth century. Gruithuisen , 1 for example, dis- tinguished fourteen qualities of gustatory sensations, while Valentin 2 recognized only two, sweet and bitter. However, the divergence of opinion here is probably due merely to the difficulties of psychological analysis. The case of the feel- ings is of a similar nature' If differences of opinion exist here, we may be sure thafiothere has never been a time when such differences did not exist. Although introspective observation has been much facili- tated and refined by the greater differentiation of mental life which has occurred in connection with the progress \ 1 Anthropologie, 1810, p. 312. 2 Grundriss der Physiologie des Menschen, 2d ed., 1847. 144 HISTORY OF PSYCHOLOGY of intellectual culture, the realm of elementary experiences with which introspection deals has remained the same. This change in complex experiences which the history of civiliza- tion illustrates is, therefore, not of immediate interest for the history of psychology. We do, indeed, occasionally find a reflex influence of complex experiences upon the conception of the elementary experiences, the significance of an experi- ence thus becoming of decisive importance for the structure of this experience itself. Olt is one of the most noteworthy characteristics in the history of psychology that the nature of a psychical event is often determined by the nature of the object upon which the idea or the desire implied in this event is directed. That which can think an eternal truth is itself eternal; that which occupies itself with sense-impressions is, like the latter, transient and perishable. This is the presupposition which led Plato to the division of man’s inner life into a higher and a lower part and which was confirmed by a very analogous distinction within the ethical field. If modern psychology describes conscious experiences as a perpetual flux of psychic processes which preserves its continuity amid its changing aspects or phases, it does so only at the end of a long, sub- jectifying process. While in the natural sciences subjective factors have been reduced, a similar process of reduction has occurred in psychology, only in an opposite direction. We are acquainted with the process of empathy ( Einfiih - lung) in which psychic contents are experienced as connected with objective contents. But there is also the opposite process in which a relationship is experienced between psy- chic states and the objects to which they refer. In so far as we have an objectification of experiences in the process of empathy, the results of such a process have been largely invalidated by the presuppositions of modern science since the beginnings of scientific reflection. The sec- PSYCHOLOGY AS A SCIENCE 145 ond form of objectification, the transference of the charac- teristics of objects to experiences, with which we have here to do, extends to a period lying within the history of psy- chology. Just as we can live over again the state of mind of a primitive man who peopled the winds and the clouds, we can in imagination transport ourselves into the mental condition of one who in the contemplation of supernatural objects feels himself as being another. But the true inward- ness of this experience we are able to judge only from its results. The presupposition mentioned, particularly in the form of the theory of an ontological affinity between that which knows and that which is known, has been from the earliest times one of the riding ideas of various systems of meta- physical psychology. We find it as a common element in the two great philosophical rivals of ancient Greece, Plato and Democritus. Both alike find within experience a cer- tain kind of knowledge having the character of intuitive certainty, which points beyond the appearances of sense, ' yvcofir ] 71/770-177. With both thinkers the content of this knowledge is the forms of reality ( ISeai ). According to Plato, however, the soul can know the eternal ideas because it is coeternal with them and remembers them from asso- ciation with them in a previous state of existence. In Democritus the ISeat are the geometrical forms of the atoms, and, since the soul itself consists of atoms, it knows objects from the minute images (I'StaAa) expressing the na- ture of the atoms which penetrate the soul. These meta- physical interpretations do, indeed, pass far beyond the range of psychology. Their common presupposition, however, is that of the identity between the content of knowledge and its bearer, between object and subject. If this presupposi- tion lapsed in the later and more genuine analysis of con- sciousness, this was due not only to the changed point of 146 HISTORY OF PSYCHOLOGY view from which experiences were regarded but also to alterations in the experiences themselves. The elabora- tion of conceptual ways of thinking tended to accentuate the cognitive aspects of experience, a process analogous to the heightening of ecstatic experience with which the belief in immortality was connected . 1 If we assume that intel- lectual experiences have lost this character of vivacity in the development of scientific thought, then the subject- matter of psychology, the experiences themselves, would, indeed, have undergone some change within the history of psychology. Aside, however, from these details, what conditions the development of fundamental psychological concepts is not so much an alteration in the experiences as a development in the point of view from which psychical facts are regarded. Perhaps it is true that psychology has been less successful in penetrating to the facts which are removed from the ordinary realm of experience than the other sciences. This is compensated for, however, by the greater change in the point of view from which mental processes are regarded. In the chapters which follow we shall try to state the more salient features of this development. In addition to the consolidation of the concept of a science of psychology there arises a gradual apprehension of the subject-matter of psychology — namely, consciousness. The different views as to what are the fundamental phenomena of consciousness appear in the attempts at a classification of mental proc- esses. No less have the methods of psychology shared in these changes in point of view. Among the theoretical con- cepts, finally, one of the most important is the concept of psychical measurement which has in modern times become fundamental for psychology, aiming at exact quantitative determinations. 1 Cf. p. 16. PSYCHOLOGY AS A SCIENCE 147 The development of the concept of psychology takes its start from the older conceptual determinations of psychology, originating within the framework of one or the other of the various philosophical systems. The problem of psychology as a science, which contained the motives out of which the modern concept of psychology developed, is of comparatively recent origin. i. Older Conceptual Formulations of Psychology ' . Since the concept of psychology as a science has become a problem only in comparatively modern times, the preceding conceptual determinations of psychology corresponding to the general tendencies of psychological thought lose some- thing of their significance. The word psychology does not occur previous to the sixteenth century. Melanchthon em- ployed the term as a title of academic lectures. R. Gockel used it in 1590 as a collective title for the works of va- rious authors. The term became generally known through Christian Wolff, who did so much for the establishment of philosophical terminology. Up to Wolff’s time the term psychosophy, apparently introduced by J. J. Becker, seems to have been in use. The term pneumatology is also found in the writings of Leibniz. If we should attempt to review the older conceptual formu- lations, we should find in the celebrated ars magna of Ray- mond Lullus, who lived in the latter half of the twelfth cen- tury, a special figura ammoe which purports to represent the whole of psychology. The soul ( S ) was symbolized by a quadrilateral figure. The three principal faculties, mem- oria, intellectus, and voluntas, are designated by the letters B, C, and D at three corners of the figure, while the fourth corner was lettered E and represented the unity of the faculties. This relation was represented by the formula, 148 HISTORY OF PSYCHOLOGY B + C + D — E. Above this figure are superimposed similar squares which turn upon the same centre, at whose corners other faculties are represented by letters, as memoria obliviens ( K ), intelledus ignorans (L), voluntas diligens vel odiens (M); whence K-\- L-\-M=N , a new condition. Four such for- mulas are required to represent the complete nature of the soul. About this whole figure revolves a second concentric one, so that we get in all one hundred and thirty-six cameras (, secunda figura S ). The great esteem in which the art of Lullus was held illustrates the tendency to formalism which has, perhaps, never been developed to the same point as in the philosophy of Scholasticism. If problems could be set and answered by shifting these concentric figures, it is merely a naive expression of the fact that in the conceptual world every correctly formulated problem has some solu- tion. We know that in mathematics or pure logic, for example, where we have to do with ideal objects, any cor- rectly stated problem can be solved, although the solution might not be explicitly statable. Once having ascertained the significance of the symbols we employ, we operate with these in a purely mechanical fashion. It is in some such manner that we might explain the great vogue of the Lullian system, although it was bound to be shattered by the impact of modern science, so great was the discrepancy between this mechanical method of juggling concepts and the empiri- cal order it purported to represent. The views which have been held at various periods regard- ing the question of psychology as a science are clearly reflected in the position assigned to psychology in the more important attempts at the classification of the sciences. In Bacon’s classification psychology is defined as philosophy of the soul ( jphilosophia humana circa animam )} It is divided into a doctrina de spiraculo and a doctrina de anima sensibili, 1 De dig. et augm. scient., 1623, IV, 3. PSYCHOLOGY AS A SCIENCE 149 hive producta. This branch of philosophy is further divided into a doctrine of the substance and faculties of the soul and a doctrine of the use and the objects of these faculties. The faculties of the sensible soul are those of movement and sensation. In his distinction between the divine and the earthly soul Bacon follows closely the example of Aris- totle. Among the faculties of the soul are also named sooth- saying and witchcraft ( divinatio and fascinatio), which are regarded as practical applications of psychology. Speaking broadly, then, we find Bacon’s conception of psychology in- cluding the traditional views of metaphysical and faculty psychology, although it must be conceded that the division of the science of the phenomena of human life was con- tinued pretty largely unchanged in the much later division into physiology and psychology. The division of psychology on the basis of faculties is also found in D’Alembert, who was the first to undertake a classi- fication of the sciences similar to Bacon’s . 1 The funda- mental faculties recognized by him are intelligence and will, the object of the former being the true, that of the latter the good. The former gives rise to the problem of logic, the latter to the problem of morals. Since D’Alembert derives the different sciences from the different objects toward which the various sciences are directed, psychology again becomes subordinated to the normative sciences of logic and ethics. Our source of information concerning the general concep- tion of psychology developed at this time is the article “Psychology,” in Diderot’s Encyclopedic. Psychology is here viewed as a branch of philosophy which defines the nature of the human soul and gives an account of its activi- ties. It divides into empirical or experimental and rational 1 Explication detaillee du systeme des connaissances humaines, 1752, CEuvres, 1821, I, pp. 102 jj. 150 HISTORY OF PSYCHOLOGY psychology. According to Diderot, empirical psychology is more important than rational psychology and furnishes the starting-point for the latter. Neither of the definitions mentioned is very definitely motived and must, of course, not be measured by a stand- ard which developed only after the possibility of scientific psychology became itself a problem. 2. The Problem of a Science of Psychology The understanding of the requirements of a scientific psy- chology was for a long time retarded on account of the fact that psychology was regarded as sufficiently defined as the science of the soul, and it was scientific only in so far as this was possible within the limits set by the metaphysical pre- suppositions regarding the nature of the soul. Only when psychology became an independent empirical science could the question of its scientific concept arise. This question reduced to the alternative as to whether psychology was in the last resort a species of metaphysics or of physics. In consequence of this alternative, psychology divided into two branches. This partition occurred in the eighteenth cen- tury, when empirical psychology was in some quarters re- garded as a branch of physics, while the older Leibniz- Wolffian school adhered to the position that it belonged to metaphysics. The profounder study of the scientific character of psy- chology on the part of Kant, whose psychological thought was otherwise largely traditional, was of real significance for the development of the science. The distinction between rational and empirical psychology Kant is generally believed to have inherited from Wolff . 1 Wolff, however, deduced the unity and the simplicity of the soul ontologically from the 1 Cf. J. B. Meyer, Kants Psychologie, pp. 220 ff. PSYCHOLOGY AS A SCIENCE 151 simplicity of substance, while Kant arrived at the idea of the soul as a simple and unitary substance from the unity and simplicity of consciousness. It is an extreme position to maintain with Herbart that Kant’s idea of rational psy- chology was picked out of the air. A more circumspect historical investigation rather shows that the Kantian for- mulation of rational psychology w r as derived from the study of Knutzen, Mendelssohn, and Reimarus. Rational psy- chology, as expounded by Kant, was literally a preoccupa- tion of the period. After the rejection of the paralogisms of rational psychology, nothing remained for Kant but empirical psychology. The investigations of such an empir- ical psychology constituted for Kant a field completely dis- tinct from his own critical task of discovering the a priori elements in metaphysics, logic, and ethics. It is important to notice this, since experience, in the sense of Kant, is the joint product of the material of sensation and of the sub- jective forms of knowledge, and since investigations of the nature of this experience would seem inevitably to become psychological in character. Nevertheless, epistemological reflection must be distinguished from the observation of the empirical mental facts. The former reveals the a priori constituents of experience, the latter the general laws of mental life. Kant draws here an extremely important dis- tinction, which has been wrongly interpreted by certain rep- resentatives of modern Neo-Kantianism as the subordi- nation of empirical psychology to the primary problem of epistemology . 1 Kant denied the possibility of systematic analysis in psy- chology on the ground that the manifold of inner observa- tion could only be separated mentally but could not be held in separation nor recombined at will . 2 His second objection 1 Cf. 3 (a), below. 2 Metaphysische Anfangsgriinde der Naturwissenschaft, Vorrede, 1786. 152 HISTORY OF PSYCHOLOGY has become better known. It was to the effect that psy- chology could never become an explanatory science since it did not admit of mathematical treatment. The only possibility would be to apply the law of constancy to the flux of inner changes. But we do not attribute to the soul anything a 'priori, except that it has temporal duration, and with the pure intuition of time we are unable to construct anything, as we can with the intuition of space, since it has only one dimension. Kant follows out the same idea in the criticism of rational psychology, which connects itself with the paralogisms of pure reason. Rational psychology is the attempt to obtain synthetic knowledge a priori, such as is obtained from the bare concept of an extended, impenetrable being, in the theory of bodies. But time, as the only form of inner intuition, can give us knowledge only of the change in the determinations of an object, never of the object itself which is determined. The ego would have to be an intuition or a concept of an object in order to yield rational knowl- edge of the nature of a thinking being, whereas it is in reality merely the form of consciousness. Kant, accordingly, thought very slightingly of the future of scientific psychology although he regarded its develop- ment in the direction of empirical anthropology as very important. Empirical psychology finds its object in the ego, as object of inner experience, or as phenomenon of the inner sense, and thus becomes anthropology or a sort of physiology of the inner sense. The relation of the inner sense to time, however, unavoidably produces uncertainty in empirical psychology which depends upon the deliver- ances of the inner sense. And since the presuppositions necessary for an experimental psychology are not met, psy- chology has to content itself with being a systematic nat- ural history of the inner sense. There are several reasons for Kant’s unfavorable opinion PSYCHOLOGY AS A SCIENCE 153 of psychology. One has to remember, in the first place, the state of empirical psychology at the time. Kant’s dispar- agement of contemporary psychologists and of their uncon- vincing explanations is everywhere apparent . 1 The only writer of whom he expected anything considerable was Tetens, whose principal psychological work, Philosophische Versuche iiber die menscliliche Natur, as we learn from a letter of Hamann’s to Herder , 2 was constantly before him. The problem of freedom proper, however, Kant writes to M. Herz, Tetens leaves entirely unsolved. The deeper reason, however, lies in the demands which Kant makes of knowledge; he demands apodictic certainty of a science in the strict sense of the word. A consciousness of uncondi- tioned necessity can only be derived from the necessary conditions of our thought, and, since these do not obtain within the realm of empirical psychology, Kant felt obliged to deny to the latter the rank of a science. Notwithstanding Kant’s opinion, however, the history of psychology shows many attempts to apply mathematics to psychology, among which the Herbartian psychology ranks supreme. The very branch of psychology concerning whose future Kant had the most serious misgivings became one of the most popular in the nineteenth century. Although Herbart’s speculations contained many unten- able presuppositions, his method of regarding the intensity of ideas in its relation to time is nevertheless based upon an incontestable formal condition of the mathematical treat- ment of psychical phenomena. The fact that the intensity of psychical processes constitutes a dimension in addition to that of time has been felt even by psychologists who do not share the conclusions of Herbart — men like Wundt, for example— as a weakening of the Kantian objection. Even 1 Cf., for example, Philosophie als Wissenschaft, 1794. 2 May 7, 1779. 154 HISTORY OF PSYCHOLOGY more sweeping is the position of Brentano , 1 who insisted upon the indispensability of mathematics in the exact treatment of any science on the ground that we come upon quantities in literally every field of phenomena. If there were no in- tensities in the realm of psychical phenomena, the theories of psychology would be essentially simpler but not less exact than now. Comte defended the possibility of the science of psychology from different points of view. Psychology, as we know, was not included in the linear arrangement of the sciences of which Comte was the author. In his Positive Philosophy the psychological material is included under the general head of biology. According to Comte, psychology, up to the time of Gall, remained entirely excluded from the great scientific movement originated by Descartes. The positive, that is, the purely scientific, doctrine of the affective and intellectual functions “consists in the experimental and rational study of the phenomena of inner sensibility belonging to the cere- bral ganglia which exist apart from all external apparatus.” 2 Since it is impossible to observe mental processes during their occurrence, psychology based upon introspection must give way to phrenological physiology in the sense of Gall. Owing to its obvious misunderstanding of the simplest facts of consciousness, the teaching of Comte did not mate- rially influence the history of psychology, and has conse- quently remained somewhat isolated. That this displace- ment of the conception of psychology was not by any means immanent in the positivistic arrangement of the sciences is shown by the classification of Herbert Spencer, which is in many respects similar to Comte’s, and in which psychology is included as an independent science following upon biology, and preparatory to sociology. The influence of Spencer’s 1 Psychologie v. empirischen Standpunkt, I, 1874, p. 86. 2 English translation by H. Martineau, bk. V, chap. VI. PSYCHOLOGY AS A SCIENCE 155 metaphysical presuppositions is evident in his view of all contents of consciousness as modifications of an ultimately unknowable spiritual substance; and in his division of psy- chology into objective and subjective psychology, the former exhibiting mental states in their relations to the stages of organic evolution, the latter deriving the simple elements by the analysis of the highest psychical phenomena, namely, the thought processes, we see the influence of his philosophical theory that all mental activity represents a differentiation and integration of states of consciousness. 3. The Modern Concept of Psychology In the controversies regarding the modern conception of psychology the old question whether psychology is meta- physics or physics returns in a new form. Psychology was obliged once more to come to terms with philosophy and with natural science. Only the roles were now inter- changed. The question now was not whether psychology was a philosophical discipline but the opposite, whether certain philosophical disciplines were not rather to be re- garded as branches of psychology. As regards the relation of psychology to natural science, with which psychology was seen to have many methods in common, the problem here was to define the boundaries of the subject-matter which rightfully fell to psychology. The relation of psychology to philosophy was worked out in connection with the movement known as psychologism. The task of relating psychology to natural science led to establishment of criteria according to which the contents of experience were to be divided into physical and mental phenomena. 156 HISTORY OF PSYCHOLOGY (a) Psychology and Philosophy: Psychologism and Its Opponents Since J. E. Erdmann the term psychologism has been applied to the view that psychology is auxiliary to and the basis of the various mental sciences. This position of psy- chology in the hierarchy of the sciences most modern psy- chologists would probably accept as an expression of the scientific temper of the time. In the narrower sense, how- ever, psychologism means the view that reality is composed of psychical contents and that the various branches of mental science, particularly philosophy, are accordingly nothing else than psychology. The sole task of philosophy is thus to make a psychological analysis of the content of experience. Of the different varieties of psychologism it is the epistemological variety in the form expounded by John Stuart Mill that has been most widely discussed. Arguments for or against a psychological tendency in epistemological questions had, of course, been current before Mill’s time. Kant had, in substance, taken a stand against psychologism when he distinguished the psychological ex- planation of judgment from its validation . 1 Beneke, on the other hand, was not less emphatic than later epistemological psychologism in proclaiming psychology as the basis of the whole of philosophy. In modern times the discussion has centred around the influential empirical logic of John Stuart Mill. In his controversy with Sir William Hamilton, Mill held scientific logic to be a part or branch of psychology . 2 Its normative character consists merely in the fact that it is a practical art rather than a pure science. In the dispute over psychological logic, which thus became the centre of 1 Uber Philosophic uberhaupt, p. 167. 2 An Examination of Sir William Hamilton's Philosophy, 5th ed.,p.461. PSYCHOLOGY AS A SCIENCE 157 the controversy, the distinction between the ideal character of purely logical laws and the empirical character of psy- chological laws was brought out with illuminating distinct- ness, as, for instance, in Sigwart’s excellent Logik (1873-8), 1 which, however, again made concessions to psychologism in the doctrine of the twofold character of the fundamental laws of logic as at once natural laws and normative laws of thought. Nevertheless, there seems to be a growing rec- ognition of the fact that the general conditions of the objects of thought which logic investigates are of a different nature from the thought processes which belong to psy- chology, a distinction which underlies a fundamental dif- ferentiation of the respective tasks of logic and psychology. 2 Psychology would be interested, as Windelband says, to determine how an idea arises; logic, on the other hand, would inquire whether the idea is valid, that is, whether or not it is true. 3 We should thus arrive at a definition of psy- chology such as that of Edmund Husserl, who in his attempts to determine the basis of pure logic emphasized the char- acter of psychology as an empirical science by assigning it the task of investigating descriptively the subjective experi- ences or contents of consciousness according to their funda- mental kinds or forms of complication, and of determining genetically the manner of their origin and decay, the causal forms and laws of their formation and transformation. 4 In his own analysis, indeed, a strongly logistic tendency made itself felt, calling forth the sharp criticism that his psy- chology merely afforded an opportunity for the application of pure logic. 5 1 [English translation, 1895. Trs.] 2 Cf., e. g., B. A. Riehl, “Logik,” in Kultur der Gegenwart, I, 6, 1908, p. 76. On the modem psychology of thought, see the dissertation of E. Durr, “Literaturbericht,” pp. 1 ff., Arch.f. d. ges. Psychologie, VI, 1906. 3 Praludien, 1884, p. 23. i Logische Untersuchungen, II, 1901, p. 336. 6 Cf. Wundt, Kleine Schriften, I, 1910, pp. 569 ff. 158 HISTORY OF PSYCHOLOGY This complete separation of these subjective experiences or contents of consciousness from the objects at which they are directed is the result of a long process of development. Originally this separation between mental acts and their objects was not made at all, in so far as this was possible in view of the rest of experience. For a long time, accord- ingly, we find a reflex influence of the objects of mental activities upon the alleged structure of those activities themselves . 1 The thought processes or the processes of volition were not regarded as constituent parts of the con- crete stream of mental events, but rather as events which were to be measured by reference to a standard or norm like truth or goodness. We have an illustration of this in the definition of D’Alembert cited above . 2 On the other hand, the reverse process took place also; the object of mental activity was resolved by psychologism into the activity itself. The logical law was now declared to be a natural law of psychology, and the conceptual relation expressed in a thought was interpreted as merely an intellectual experience. For the purely logical relation expressed by the law of contradiction, namely that contradictory predi- cates cannot belong to the same subject at the same time, psychologism substituted the real incompatibility of two mutually contradictory acts of judgment as empirical mental processes in the same mind. It was only in contrast with these various forms of usurpation that the view of mental states as independent realities emerged. Of course, efforts were hereby not excluded to maintain a connection between psychology and epistemological prob- lems, a connection which would seem to be inevitable, owing to the fact that all processes of knowledge are presented in individual experience. Paul Natorp declared the subject- matter of psychology to be the subjective aspect of experi- 1 Cf., p. 144. 2 Cf. p. 149. PSYCHOLOGY AS A SCIENCE 159 ence, prior to all processes of objectification. Now, since the fundamental laws of objectification and the laws which immediately complete the process of objectifying the phe- nomena are different from each other in the same sense in which the a 'priori constituents of consciousness are different from the empirical, it is possible to distinguish a purely a priori part of psychology, which can be referred to phi- losophy as a correlate to the purely objective criticism of knowledge . 1 A still closer affiliation of psychology with philosophy is found in H. Cohen. The task of psychology within the general field of philosophy is to deal with the problem of the unity of social consciousness. It is true, psychology describes consciousness according to its ele- ments; but these elements are necessarily hypothetical, since it is impossible for one who operates with consciousness to lay bare that with which consciousness really begins . 2 This hypothetical character of the elements of consciousness, to be sure, seems to conflict with the characterization of mental elements expressed elsewhere ; 3 still, it must be remembered that the fundamental conception of psychology as a philo- sophical science which is in question here is distinctly differ- ent from the conception of an empirical science, which also represents the result of the effort to articulate psychology with natural science. iff) Psychology and Natural Science: Differentiation of Physical and Psychical Phenomena To the definition of psychology bequeathed by metaphys- ics as the science of the soul has been opposed the definition of it as the science of mental phenomena . 4 The latter defi- 1 Einleitung in die Psychologie nach kritischer Methode, 1888, pp. 43, 124. 2 Logik der reinen Erkenntniss , 1902, p. 16. 3 Cf. Chapter VII, 3, below. 4 Cf. F. Brentano, Psychologie v. emp. Standpunkt, I, pp. 10 ff. 160 HISTORY OF PSYCHOLOGY nition was prompted by the same motive as prompted critical reflection to discontinue the old definition of physical science as the science of bodies, and to substitute therefor the defi- nition of it as the science of physical phenomena. The in- sight which was obtained early in the history of philosophy that the objects of what is called external perception are only phenomena Locke once illustrated by a celebrated psychological experiment. Having warmed one hand and cooled the other, he plunged both into the same vessel filled with water, with the result that one hand perceived cold while the other perceived warmth. But since warmth and cold could not exist simultaneously in the same water, he regarded the phenomenal nature of these perceptions as proved. In the application of this concept of appearance to the realm of inner perception, which came much later, an effort was made to avoid the implication that mental contents were the states of a substance. This is illustrated in the definition of psychology accepted by John Stuart Mill , 1 who asserted the task of psychology to be the investigation of the course of mental states, which was controlled, accord- ing to him, by the well-known laws of association . 2 In con- nection with complex phenomena the question arises as to whether they can be explained as the joint products of men- tal processes or whether they are to be regarded as novel formations. The phenomenalistic point of view, however, disclaims any intention of limiting the task of psychology. The definition of psychology as the science of mental phenomena has been represented on the Continent by Franz Brentano . 3 Brentano is particularly interested in the cri- teria according to which mental phenomena can be unam- biguously distinguished from physical. The characteriza- tion of mental phenomena as distinguished from physical i Logic, VI, chap. 4, § 3. 2 Cf. p. 101, above. 3 Op. cit., 101 ff. PSYCHOLOGY AS A SCIENCE 161 has often been merely negative. Originally the distinguish- ing feature was spatial. Physical phenomena had extent, while mental phenomena, thinking, willing, and the like, had neither extent nor any other spatial characteristic. This served as the differentiating mark in the metaphysical systems of Descartes and Spinoza, and it was adopted by Kant, who regarded space as the form of outer sense. Still more recently inner experience has been defined negatively by Bain on the basis of the absence of spatial attributes . 1 The objection has been urged against this criterion that there are also physical phenomena which do not have the attribute of extent. Tones and odors have always been denied an original spatial quality. Berkeley even denied spatial characteristics to color, Plattner to taste impressions, and many psychologists from Hartley to Herbart and Spen- cer have not admitted that space is an original attribute of any phenomenon of the outer sense. Convinced of the inadequacy of these negative definitions, Brentano en- deavored to find some positive characteristics of mental phenomena which would distinguish them unequivocally from physical. The most important one of these he found to be the “intentional” character of psychical phenomena: they are phenomena which intentionally contain an object. A second characteristic given by Brentano is that they are discoverable only by introspection, thus reverting in a pecu- liar way to the old doctrine of inner sense . 2 In addition to this phenomenology of consciousness rep- resented by Brentano and his school there is observable a second main tendency which determines the relation between psychology and natural science by the point of view from which an item of experience is to be regarded. The example of natural science suggested to psychology a treatment of its objects in analogy with the treatment of natural science. 1 Mental Science, 1868, Intr., chap. I. 2 Cf. p. 84, above. 162 HISTORY OF PSYCHOLOGY Thus Rickert maintained that psychology must transform the manifold of psychical experience into a conceptual order, just as natural science substitutes a conceptual order for the manifold of sense experience . 1 This demand was most completely met by Miinsterberg. For Miinsterberg the object of psychology, like the object of natural science, is a product of abstraction. It came into existence logically through the fact that reality was objectified, the value objects of the actual ego thus detached from the subject, and actuality transformed into experienceable processes. Within this objectified world natural science and psychology were differentiated in such a manner that the latter had to do only with objects which exist solely for the activity of one subject . 2 On the other hand, the necessity for such a conceptual translation has been denied on the ground of the direct, immediate reality of the experience to be thus transmuted. This position has been taken by Wundt, who has defined psychology tersely as the science of immediate experience, thus supplementing natural science, which is the science of mediate experience. Faithfully as this view of psychical facts as a sphere of reality of equal validity with the reality of mediate experience champions the rights of psychology in its relation to natural science, nevertheless the epistemo- logical presuppositions underlying this distinction, in conse- quence of which conscious experience and objects differ only according to the point of view adopted, have often been controverted, particularly by the representatives of act psy- chology. In recent times decided doubt has been cast upon all these distinctions. The modern opponents of metaphysics have tried to drive the old metaphysics out of its last lurking-place. 1 Grenzen der naturwissenschaftlichen Begriffsbildung, I, pp. 183 ff. 2 Grundziige der Psychologie, 1900, p. 202. PSYCHOLOGY AS A SCIENCE 163 This tendency produced the empiriocriticism of Mach and Avenarius , 1 which recognized everything which we immedi- ately feel as a complete experience. While the customary distinctions between physical and psychical lead to manifold ambiguities, the new definition of the psychical asserts the object of psychology to be that aspect of a complete experi- ence of an individual which is dependent upon the individual for its existence. Instead of the older opposition of nature and spirit bequeathed by naturalistic modes of thought, we now have as the constituents of our psychical life psychical experiences, determinate sensations of color, tones, and so forth, which stand on precisely the same footing as the con- tents of inner experience . 2 In the terminology created by Avenarius, which substituted for the individual the nervous part system C, this definition tends to assume a materialistic hue, from which, however, it later freed itself by the suppres- sion of the insidious system C. The enticing doctrines of empiriocriticism have occa- sionally been responsible for an unhistorical polemic against psychology like that of R. Willy, for example, who has ex- pressed the opinion that psychology is at the present time undergoing a crisis, and has sought to show that the systems of Wundt, Rehmke, and Brentano really rest upon a meta- physical spiritualism . 3 The point of his criticism is that the attempts to assign psychology a special subject-matter, like Rehmke’s psychical concrete or Brentano’s psychical phe- nomena, do not, in spite of their pretence at pure empiricism, escape spiritualistic metaphysics. But psychology, which has so often been the target of epistemological attacks of this sort, will survive this criticism also, deeds being more con- vincing than words. 1 Vierteljahrsschrift f. wiss. Phil., XVIII, 1894, 137, 400; XIX, 1895, pp. 1, 129. 2 Cf., e. g., H. Cornelius, Eirileitung in die Philosophic, 1903, pp. 177 ff- 3 Vierteljahrsschrift f. wiss. Phil., XXI, 1897, pp. 79, 227, 332. 164 HISTORY OF PSYCHOLOGY One question as to the future. If psychology, according to the modern conception developed here, is to bear the same fundamental relation to the mental sciences as physics bears to the natural sciences, there must exist in connection with psychology a certain border realm similar to the philosophy of nature affiliated with natural science. It might be con- tended that the history of metaphysics, in which philosoph- ical points of view have dominated, shows plainly enough how wddely the latter are relinquished by the modes of thought of a truly empirical psychology. Still, there is a second way in which the phenomena of consciousness can be considered, a way which has its counterpart in the inves- tigation of the presuppositions of the exact sciences. As one investigates here the basis of hypothetical constructions and the significance of axiomatic assumptions, so it is possible to raise the question in psychology as to the nature of the fundamental hypotheses employed, and whether there are also in this field propositions of axiomatic significance. The history of epistemology and of ethics illustrates the abun- dant attempts to discover primitive relations among con- tents of consciousness which exhibit axiomatic character. These have always been measured by a logical or ethical norm. Thus it was taught, for example, that there existed a necessary connection between the true knowledge of a moral good and the act of will directed to the production of this good. For concrete volitional experiences, however, no such axiomatic principle obtained. A few such propositions which have a principial significance for empirical psychology have indeed been exploited , 1 and we shall come upon them again in the discussion of the special fundamental concepts of psychology. Nevertheless, the problem itself belongs to the future. It is possible that reflection upon the hypothet- ical principles underlying psychology will open to us vistas 1 Cf. p. 142, above. PSYCHOLOGY AS A SCIENCE 165 as far-reaching as the theory of relativity, for example, in modern physics . 1 1 [For the latest conceptions of psychology as discussed at present, particularly among American psychologists, cf. esp. Angell, “Behavior as a Category of Consciousness,” Psych. Rev., 1913, pp. 255-270, and Watson, “Psychology as the Behaviorist Views It,” Psych Rev., 1913, pp. 158-177. Trs.] CHAPTER VI THE SUBJECT-MATTER OF PSYCHOLOGY: CONSCIOUSNESS Considering how far back reflection on psychological questions extends, the real subject-matter of psychology was late in receiving conceptual formulation. As qualities or functions of a metaphysically defined soul, psychical con- tents were mere manifestations, much in the same way that natural processes were the manifestations of physical bodies which acted as their bearers. It was only when psychical contents were viewed in their immediate reality as parts of a unified field of experience that psychology acquired a defi- nite subject-matter. The development of the concepts of consciousness merely means, therefore, the gradual appre- hension of psychical contents in their immediate reality as conscious experiences. The question whether the concept of consciousness is wide enough to include the entire range of psychical events has given rise to controversies concern- ing the limits of consciousness, which have centred princi- pally about the question of the significance of the uncon- scious in psychology. Another and different problem was that of the range of consciousness, which led to the consid- eration of the graduation of conscious contents according to degrees of clearness. The latter connected itself mainly with the accentuation of special conscious contents in the experience of attention. i. The History of the Concept of Consciousness (a) Early Developments of the Concept The problem of consciousness can hardly be said to have existed for the philosophy of antiquity. It is true that 166 THE SUBJECT-MATTER OF PSYCHOLOGY 167 Plato points to the necessity of reflection (cfrpovrjo-is) and of self-knowledge, but the notion of self-knowledge is much too narrow to serve the purpose of defining the boundaries of the subject-matter of psychology. The consciousness to which Plato refers is the consciousness of what our experi- ence objectively signifies. Here, too, we see how the object at which psychical activities are directed becomes normative for those activities themselves . 1 The limitation of ancient psychology referred to reveals itself with particular clearness in Aristotle’s attempt to determine the boundaries of the psychical. Psychology, according to Aristotle, has to do with the phenomena of life in plant, animal, and man. But w T e find no criterion by which we are to distinguish psychical phenomena from vital processes in general. Even in the consideration of specific psychical contents there is no attempt to point out any common characteristic which belongs to them as contents of consciousness. Neither the arrangement in a hierarchy of lower and higher functions, in which the conscious func- tions are naturally classed together, nor the distinction between the perception of a sense-impression and the per- ception of this perception itself, between the thought of an object and the thought of the thought , 2 yields any formula which comprehends the whole of consciousness as such. Suggestions of the concept of consciousness are found in Aristotle only in connection with the metaphysical treat- ment of the fact of self-consciousness, as in that memorable passage in the Metaphysics which describes the nature of God . 3 God alone, who is pure activity ( actus purus), thinks himself, his thought being his sole object. The characteristic thought of, in the first instance, merely as self-consciousness was destined to expand into the general concept of consciousness. This step, as has been shown, 1 Cf. pp. 144 /., above. 2 Cf. p. 72, above. 3 XII, 8, 9. 168 HISTORY OF PSYCHOLOGY was not taken until Neo-Platonism . 1 The Neo-Platonic interpretations of the concept of consciousness were partly based upon the thesis that that which cannot know itself cannot know anything else. According to Plotinus, the soul comes to self-consciousness through its vision of the Nous. The result of this act is an identity of the vow, vorja^ and vorjTov. This is a description of the experience of self- consciousness which is at once mystical and sensuous. More important, however, is the fact that Plotinus ascribed to the Nous, which he defined as a manifold containing within itself the principle of unity , 2 the attribute of self-consciousness (crvvaLcrdricus ainrjs), and thus gave general currency to an expression which had occurred only occasionally in writers like Alexander of Aphrodisias and Galen. From now on the definite separation between consciousness and the uncon- scious possession of an idea becomes customary among the Neo-Platonists. To the activities of sensation, presenta- tion, etc., is superadded an accompanying consciousness (irapaKoXovdrjcns) which is further described as an activity of reflection ( avcuca/JLTrTovcrrp ? t Siavoia<;). While, therefore, the distinctive character of conscious- ness as such remains unrecognized, the problem of con- sciousness emerges more distinctly than before. The em- phasis upon the inner man in the teachings of Christianity was also bound to assist the process of psychological self- reflection. In Augustine the knowledge by the soul of itself is one of its most assured possessions. Even if we should doubt the existence of the outer world, this very doubt would assure us of our own psychical existence. The fact that Augustine found an epistemological basis in the imme- diate deliverance of self-consciousness, an insight of great moment to the future of philosophy, shows how vitally he grasped the fundamental psychological principle involved. 1 Siebeck, op. cit., I, 2, pp. 337 ff. 2 Enn., V, 9, 6. THE SUBJECT-MATTER OF PSYCHOLOGY 169 For a thousand years, however, this thought remained un- developed. It became merged with the doctrine of the inner sense, as in Thomas Aquinas, for example, who, not- withstanding his theory of inner perception , 1 gave the col- orless description of self-consciousness as an act of knowl- edge in which spiritual substances return upon themselves. ( b ) Development of the Modern Concept of Consciousness The discovery of consciousness as a fundamental psychi- cal fact was not made before Descartes. It is true that Descartes was influenced in many of his psychological views by that bold empiricist Vives . 2 Nevertheless, his distinction between extended and thinking substance was tantamount to the designation of the field of psychical phenomena or contents of consciousness as a permanent subject-matter of psychology. It has been asserted that psychology, in so far as it was not metaphysical, had not made any impor- tant advance over Aristotle up to the time of Descartes. It is certain, in any case, that the discovery of Descartes introduced a characteristic difference between modern psy- chology and the psychology of Aristotle. Descartes clearly enunciated the truth that the appearance of a psychical con- tent was identical with the consciousness of the same . 3 This has remained the point of departure for empirical psy- chology; it was already self-evident for Locke that to have ideas and to be conscious of them was one and the same thing . 4 In keeping with its origin in epistemological considera- tions, the Cartesian concept of consciousness has partly 1 See p. 74, above. 2 This has been emphasized particularly by Hoffding, Geschichte d. n. Phil., I, p. 259. 3 Princ. Phil., I, 9. i Essay on the Human Understanding, bk. II, chap. I, § 9. 170 HISTORY OF PSYCHOLOGY been refined in modern psychology in an epistemological direction, and it has partly been freed from the strictly intel- lectualistic character given to it by Descartes, according to whom all conscious contents consist in cognitive processes. It was not until these modifications occurred that the con- cept was wide enough to include equally all psychical phenomena. The first of these developments led to considerable dif- ferences in point of view in the treatment of self-conscious- ness. The empirical point of view which sought to resolve the fact of self-consciousness or the ego into empirically given contents of consciousness was never more brilliantly represented than by David Hume. The upshot of his criti- cism was the total rejection of the idea of soul substance, on the ground that such a substance always presupposed the spatial connection of the contents of consciousness with something extended or inextended. Just as little are we able to discover in personal identity or the ego the principle of unity within consciousness, as philosophers have claimed. “Our notions of personal identity proceed entirely from the smooth and uninterrupted progress of the thought along a train of connected ideas .” 1 The opposite tendency reached its climax in post-Ivantian philosophy. Kant’s much admired doctrine of the unity of transcendental apperception found in self-consciousness that relation between the contents of consciousness and a self which Fichte erected into a philosophical principle. Ever since the Neo-Platonists compared this inexpressible rela- tion between the ego and the contents of consciousness with the relation between the centre of the circle and the circle itself, many thinkers have sought to give an answer to this riddle which continues to stand at the threshold of psy- chology. They were all surpassed by Fichte, however, when 1 Hume, Treatise of Human Nature, bk. I, part IV, § VI. THE SUBJECT-MATTER OF PSYCHOLOGY 171 he undertook to evoke the whole universe from the bare fact of this relation to the ego. The glorification of the fact of self-consciousness which his constructions implied aroused the protests of more cautious psychologists. Fichte’s doc- trine of self-consciousness may be summed up in the follow- ing formula : The ego is that which thinks itself. Herbart proved the imsoundness of this formula by showing that it involves an infinite regress. The “itself” can, in turn, be nothing else than the self, so that the Fichtean proposi- tion is equivalent to the proposition: the ego is that wdtich thinks itself, etc., ad infinitum. Of greater significance for psychology was the extension of the concept of consciousness to include all psychical phenomena already suggested in Leibniz’s important doc- trine of the grades of consciousness, in virtue of which all conscious states pass into each other by continuous trans- itions. To express this unique character of consciousness Leibniz employed a terminology partly invented by him- self. He used the old word perceptio, in the first place, to indicate the unconscious, passive state of the monad, in which it represents only the external world. Opposed to this is the conscious state, designated by the newly coined word apperceptio, which is that activity of the monad through which it becomes aware of its own percep- tions. The word consciousness, meanwhile, passed into phil- osophical usage as a translation of conscientia. This has, in spite of many shifts of meaning, retained the ethical significance of conscience, illustrating how the concept of consciousness is foreshadowed in the terminology of ethico- religious reflection. It is true that the Stoics already used the philosophical terms avveiSrjcns (consciousness) and avv- aiadr)cn<; erven aaecos (self-consciousness), with which Sen- eca first associated the term conscientia. In conscientia, however, the ethico-religious significance of conscience re- 172 HISTORY OF PSYCHOLOGY mained predominant, for which the much-disputed term synteresis was used in the Middle Ages. The etymology of this word, as we learn from Albert von Bollstadt, was already in dispute in Scholastic philosophy. Attention has recently been called to the fact that r rjprjcns was used by certain physicians of the latter half of the Middle Ages as the terminus technicus for observation. According to the use of aw a icr 9 ye is or cri weiSyais by Stoicism, and still more by Neo-Platonism, awrypycns would thus, in the first instance, have meant self-observation. If the deriva- tion suggested here is correct, the history of this concept offers an instructive example of the fact that a term of purely psychological import which had been restricted to an ethico-religious signification had its original meaning restored only by the roundabout way of translation. 2. The Concept of the Unconscious (a) Representatives and Opponents of the Notion of the Unconscious The concept of consciousness in Leibniz was so compre- hensive as to include the notion of the unconscious as well. The idea of petites perceptions gave rise to the idea of a monad filled at each moment with an infinite number of perceptions. Since any number of intermediate stages may exist between a given grade of consciousness and the state of unconsciousness, the petites perceptions need to be only relatively unconscious. Leibniz gives a number of reasons why the petites perceptions do not possess the degree of consciousness of ordinary conscious contents. They are either too weak to rise to consciousness or they occur in such large numbers as to makU.The consciousness of the separate ones impossible. Finally, they may be crowded out by other particularly strong contents of consciousness. THE SUBJECT-MATTER OF PSYCHOLOGY 173 It is possible that Leibniz is here influenced by the older view of Malebranche , 1 who had deduced the original uncon- sciousness of so many ideas from the impossibility of their simultaneous apperception. These are reflections which anticipate later views in a remarkable way and which illuminate strikingly the significance of this concept of degrees of consciousness for the subsequent efforts of psy- chical mechanics. But with the sharp separation of perceptio and apper- ceptio and the recognition of perceptiones insensibiles Leibniz approaches the conception of the unconscious, while he abandons completely the idea of a hierarchical arrangement of conscious contents on the basis of degrees of clearness, assuming the existence of innate and, in the strict sense, unconscious mental contents. In the polemic with Locke, who takes his stand on the ground of psy- chological experience, the rationalism of Leibniz gains the upper hand. In the criticism of Locke’s theory of knowl- edge Leibniz maintains the existence of innate and uncon- scious contents said to contain the principles of theoretical and practical reason. The notion of these unconscious con- tents approaches to some extent that of psychical disposi- tion, and Leibniz, indeed, sought to render their existence vivid by comparing them with memory contents . 2 Leibniz’s doctrine of unconscious psychical contents read- ily passed over into a number of very diverse psychologi- cal tendencies, he himself having thrown out suggestions for various applications of the idea. It was introduced into association psychology by the elder Mill, who spoke of sensations which, on account of habitual inattention, do not rise to the level of consciousness at all. Hamilton pointed to unconscious intermediate links which we are 1 Rech., Ill, 27, and VI, 1, 5. 8 Philosophische Werke, ed. Gerhard, V, p. 75. 174 HISTORY OF PSYCHOLOGY obliged to assume in order to make the connection of our ideas intelligible, and Lewes went still further with the claim that the great majority of conscious processes ran their course unconsciously. In Maudsley, finally, uncon- scious psychical activity became a fact so incontroverti- ble as even to demand the physiological treatment of psy- chology. The concept of the unconscious is developed in a different direction by Herbart. According to Herbart, those ideas are unconscious which lie below the threshold. True, they do not represent actual presentation, which can take place only above the threshold, but only a tendency to presenta- tion. At the same time they act upon one another accord- ing to the same laws which govern actual presentations. As an auxiliary conception which was meant to explain conceptual processes, the idea of unconscious inference came to play a part in the later spatial theories of Helmholtz and Zollner. The many-sided utility of the concept of the unconscious shows itself, finally, in the fact that it was invoked to extricate the ego doctrine of Fichte from the difficulties in which it had become involved in connection with the problem of self-consciousness. Schelling in this way arrived at a purely speculative deduction of the uncon- scious . 1 The production of the world can never be com- prehended by beginning with an ego already conscious of itself. But the ego which has become conscious of itself can look back upon a moment of its own activity in which it was not as yet conscious of itself, and thus the beginning of the ego’s activity retreats into the realm of the uncon- scious. With all his appeal to the facts of psychological experience, large concessions were later made to the notion of the unconscious by Hartmann in his Philosophy of the Unconscious. 1 Werke, Abt. I, vol. Ill, pp. 348/. THE SUBJECT-MATTER OF PSYCHOLOGY 175 Over against this large number of champions of the doc- trine of the unconscious we find a second group of think- ers, no less influential than the former, who oppose the doc- trine. It was rejected by the leading English psychologists, J. S. Mill, Bain, and Spencer, and by H. Lotze in Germany. Ulrici also denied the existence of unconscious psychical activity, although his own concept of consciousness, of course, differs from the usual one . 1 Fechner’s fundamental psychological law, indeed, led him to a point beyond which a conscious correlate of psychophysical activities disappears. Nevertheless, he evaded the assumption of unconscious sensations and ideas by holding that only the psycho- physical activities persisted . 2 Wundt, who in his earlier psychological writings 3 still admitted unconscious inference, which seemed to be so important for the theory of percep- tion, later took stand against the assumption of uncon- scious psychical activity. In order to satisfy the demands of explanatory psychology Lipps, indeed, fell back upon unconscious psychical processes. The appearance of these processes, however, are, even in Lipps, always accompanied by consciousness. (b) Arguments for and against the Unconscious The various lines of thought in the controversy over the unconscious can be best followed if presented in the form of the arguments for and against the unconscious which were put forward by the participants in the discussion of the question . 4 As is the case in so many fundamental con- cepts of psychology, the demand made was partly one of 1 Cf. p. 80. 2 Elemente der Psychophysik, II, 1860, p. 438. 3 Beitr&ge zur Theorie der Sinneswahrnehmung , 1862. See also his Lectures on Human and Animal Psychology , 1863. 4 Cf. F. Brentano, Psych, v. emp. Slandpunkte, 1874, pp. 137 ff., which the present discussion partly follows. 176 HISTORY OF PSYCHOLOGY explanation, partly one of description. The arguments ac- cordingly fell into two classes, in the first of which the unconscious is invoked in the service of causal explanation, and in the second of which difficulties are pointed out in the pure phenomenology of consciousness which cannot, it is held, be solved without having recourse to the hypothesis of unconscious psychical phenomena. The difficulties raised by the demand for causal explanations were obviously greater than those presented by the task of pure description. An unconscious psychical process was accordingly invoked either as the cause of an empirical conscious process, or else the attempt was made to prove the existence of uncon- scious psychical processes on the basis of an inverted causal relationship. The former and more natural use of the unconscious is the one most frequently found. Thus Sir William Hamil- ton argued for the existence of unconscious ideation from the occasional absence of a series of intermediate terms in the revival of a previous train oLassociation . 1 However, no one who agreed with Hamilton in his assumption has been able to show that this explanation is the only possible one. The same applies to F. A. Lange, who explained the phe- nomenon of the blind-spot by supposing that the eye un- consciously infers the color which it should actually see. The theories of space of Helmholtz and Zollner operated with the notion of unconscious inference, without utilizing the auxiliary aids employed by the psychology of the time in order to do justice to the facts without invoking uncon- scious intermediate links. Maudsley and Lewes sought to show by the phenomena of reproduction that experiences which rose to consciousness in dreams or in recollection may originally have existed as unconscious psychical phe- nomena. All these arguments finally combine in Hart- 1 Lectures on Metaphysics and Logic, I, Lecture XVIII. THE SUBJECT-MATTER OF PSYCHOLOGY 177 mann, who, indeed, goes beyond immediate experience in so far as he regards conscious and unconscious phenomena as heterogeneous, the hypothesis of the unconscious thus losing much of its significance for empirical psychology. Unconscious psychical phenomena do not conform to the laws of experience but dissolve into an eternally uncon- scious and unique reality possessing wholly transcendental attributes . 1 The second line of speculation which views unconscious psychical acts as the effects of conscious psychical acts is encountered less frequently. A consideration of this sort goes back to Leibniz. An ocean wave produces the roar of the breakers, but if it is only a drop of water which falls we hear nothing whatever. But we must have an audi- tory sensation even in the latter case, for the noise of the wave consists of the simultaneous noises of the single drops which compose it. An analogous idea is utilized by Ulrici for visual sensations. Although very small objects are not perceptible, they nevertheless yield some visual impression. For larger objects are perceptible only because the visual perception is the result, as it were, of a number of sense- impressions which separately are so weak as to escape at- tention . 2 This conclusion has been contradicted by the pretty generally recognized principle of modern psychology that the sum of effects is not merely quantitatively different from the separate members or components, but qualitatively as well. The fact that the after-image shows details which were not observed in the original image was also cited by Ulrici in support of the assumption of unconscious sensa- tions . 3 Helmholtz, too, has given a circumstantial account of similar phenomena . 4 Still, it has never been proved that 1 Philosophie des Unbewussten, 2d ed., pp. 473 jf. 2 Gott und Mensch, p. 294. 3 Op. cit., pp. 285 and 304. 4 Phys. Optik, p. 337. 178 HISTORY OF PSYCHOLOGY the sensation in question was actually unconscious, and the newer analysis of the processes of attention has suggested less hypothetical explanations of the phenomenon con- cerned than the one here employed. More convincing than the lines of reflection just enumer- ated was the assumption that the strength of the conscious- ness accompanying a given psychical activity stands in a functional relation to the strength of the latter. With sufficient diminution of the degree of strength of the psychical phenomenon, consciousness could disappear entirely. It was on the basis of such considerations that Beneke ad- mitted the existence of unconscious psychical activities . 1 The doctrine did not make much headway, however, as the notion of psychical measurement, which the idea of the strength of psychical activity suggested, tended in Fechner to ignore unconscious sensations and to put in their place the vague notion of psychical disposition. Brentano, moreover, broke the force of the argument for the uncon- scious by considerations of a purely psychological character . 2 The intensity of presentation is always equal to the intensity with which the presented content appears. The intensity, therefore, of the presentation of a presentation must be equal to the intensity with which this presentation itself appears. In virtue of the veridical character of inner per- ception, the apparent intensity of conscious presentations and their actual intensity coincide. We thus arrive at the conclusion that in the case of any conscious presentation the strength of the presentations referring to it is equal to its own strength. This line of reflection is really less significant as a refutation of Beneke than as a characteristic of Brentano’s psychology. A conclusion which at the out- set is not by any means self-evident will follow necessarily from presuppositions every one of which must be admitted 1 Lehrb. d. Psych., 2d ed., § 57. 2 Op. tit., p. 157. THE SUBJECT-MATTER OF PSYCHOLOGY 179 if one accepts as one’s point of departure the conception of Brentano’s psychology as the doctrine of psychical phe- nomena given in inner perception. The other principal line of evidence for unconscious psychical activities depending upon the presuppositions re- quired in a purely descriptive account of conscious phe- nomena made capital of the enormous complication which the assumption that any psychical activity was a conscious activity was said to necessitate. If an unconscious psychical phenomenon is an impossibility we should have to assume, in addition to the presentation of a tone, the presentation of this presentation. The second presentation, in turn, if it is to be conscious, requires another presentation of it- self, and so on, the simple act of audition thus forcing upon us the assumption of an infinite number of such psychical activities. Reflections of this sort arose particularly in connection with the doctrine of the inner sense. This dif- ficulty connected with the doctrine of the inner sense had already been pointed out by Aristotle in the De Anima. The first writer to deduce from this difficulty the existence of unconscious psychical activities was Thomas Aquinas . 1 In modern times Herbart referred to the fact that among the various masses of ideas, each of which apperceived the preceding one, one must hold the ultimate or highest place, and that it cannot itself be apperceived . 2 For Herbart, of course, the existence of unconscious ideas was already assured on other grounds. Although the difficulty of in- definite complication of mental states has often been dis- cussed, it has seldom supplied a real argument for the ex- istence of unconscious psychical phenomena. Attempts have sometimes been made to solve this problem without resorting to the assumption of unconscious psychical phe- 1 See p. 74. 2 Psychologit als Wissenschaft, Teil II, Absch. II, Kap. 5, § 199. 180 HISTORY OF PSYCHOLOGY nomena by asserting that the psychical activity and the objects toward which it is directed are one and the same phenomenon. Bain, for example, asserted the same iden- tity of activity and object in the various kinds of sense- impressions as he believed to exist in the so-called affective sensations. A closely related position is that of J. S. Mill. We see foreshadowed here the concept of consciousness as immediate experience in which the two terms of act and content, usually kept distinct, are identified, as, for example, in the psychology of Wundt. Starting from his own point of view, Brentano undertook the solution of the problem in a different manner. He made his beginning with the question as to the relation between the presentation of an object and the presentation of this presentation, and he found the idea of a peculiar coalescence of the object and its accompanying presenta- tion a common one among psychologists. Aristotle had already made the observation that a conscious phenomenon must include within itself the consciousness of itself . 1 More clearly than in the case of sense-perception, he described the peculiarity of inner experience in his Metaphysics to the effect that knowledge, sensation, opinion, and reflection were always directed toward something else, but secondarily also toward themselves. Practically all authorities who deny unconscious activities agree with this description in the main. So J. S. Mill, for instance, according to whom sensations apprehend themselves, and Lotze, according to whom a consciousness of psychical phenomena accompanies the phenomena. Ulrici, too, regarded all our sensations as at the same time sensations of ourselves; and even in Beneke the accompanying consciousness was treated as a special attribute of the psychical phenomenon, given with the latter . 2 In Brentano’s psychology, after the statement that every psychical phenomenon is the consciousness of 1 De Anima, III, p. 2. 2 Lehrb. d. Psych., 2d ed., § 57. THE SUBJECT-MATTER OF PSYCHOLOGY 181 an object, the opposite question, whether every psychical phenomenon is the object of consciousness, is raised in the paradoxical form whether an unconscious conscious- ness exists. If the term unconscious is here understood in the passive sense of an object of which one is not conscious, an unconscious consciousness is as free from con- tradiction, as, for example, an unseen act of seeing . 1 An- alysis, however, tended to abandon the notion of an un- conscious consciousness in the above sense, since it showed that the presentation of a tone, for example, and the pres- entation of this presentation are one and the same thing . 2 The foundation seemed thus to be removed from under the notion of the unconscious from the standpoint of the pure phenomenology of consciousness also. 3. The Range of Consciousness Aside from these attempts to draw the boundary-lines of consciousness, certain other considerations regarding the range of consciousness have been of no less importance. While the determination of the boundaries of conscious- ness tended naturally to become a speculative question, the problem of this content of consciousness tended from the first to take on an empirical and special character and pre- ceded to some extent the development of the concept of consciousness itself. The fact that only a limited number of psychical contents could be present in consciousness simultaneously forced it- self upon the attention of observers at a very early stage of scientific reflection. Diogenes of Apollonia is reported to have referred to a competition among the various sense departments for a part in a limited amount of mind stuff . 3 1 Op. cit., p. 133. 2 Op. cit., p. 167. 3 For a history of the attempts to determine the range of conscious- ness, see W. Wirth, Die experimentelle Analyse der Bewusstseinspha- nomene, 1908, pp. 56 ff. 182 HISTORY OF PSYCHOLOGY For a long time scientific curiosity regarding the problem in question seems to have been satisfied by the assertion of Aristotle that several objects could be apprehended simultaneously, to which he added certain other observa- tions concerning the relation of similar and opposite ideas . 1 It was not until the time of Scholasticism that we find in John Buridan a more careful investigation of the possibility of a plurality of simultaneously existing psychical states . 2 Buridan asked the question, a question new to his time, as to the degree of clearness with which simultaneous pres- entations could be perceived. Now every perception, no matter how simple, is composed of a multiplicity of parts. As a rule, it is not the parts which are perceived, but the whole. When the object is very large, on the other hand, the parts are perceived more distinctly than the whole. If a number of sensations are presented simultaneously the distribution of clearness among them is not uniform. These observations of Buridan, fragmentary as they are, stand out in clear relief against the attempt often made in the Middle Ages to limit thought ( intelligere ) to one presenta- tion at a time, an idea revived in the Herbartian school of psychical mechanics and ironically called the needle-eye theory of consciousness. In modern psychology the problem of the range of con- sciousness arose in connection with certain epistemological distinctions in Locke, to whom the narrowness of con- sciousness was a familiar concept, and who discussed the psychological distinctions between clear and obscure, dis- tinct and confused ideas . 3 A chiliahedron and a figure of nine hundred and ninety-nine sides can be distinguished if we confine ourselves to that part of the two ideas indicated by the final digits, as, for example, when we consider that 1 See p. 89. 2 De sens., 21. 3 Essay on the Human Understanding, II, chap. XXIX, esp. § 14. THE SUBJECT-MATTER OF PSYCHOLOGY 183 the number of sides is divisible by two in the one case and not in the other. A difficulty arises, however, when we try to distinguish the two figures by their actual appearance in perception, since we can form no distinct images of the two figures in the mind, as we can, for instance, of a figure of four and one of five sides. Aside from the insight that there was some sort of limit to the number of clear, simple ideas con- tained within a complex idea, the statement that this limit was not exceeded by four or five such component parts has acquired a special significance from later experimental veri- fications. With much sympathy and intelligence Bonnet subse- quently undertook to deal with the question, which arose in many different connections, as to whether a number of presentations could appear in consciousness simultaneously. He took a decided stand against the Wolffian school, which tended to take the older Scholastic view of the restricted range of consciousness. The arguments of the Wolffians were partly metaphysical, as when they reasoned that it would contradict the notion of the simplicity of the soul if it could be modified variously at one and the same time; they were partly based upon the consideration of the temporal succession of ideas in consciousness, which made it impos- sible for more than one idea to arise in a given moment of this temporal series. Bonnet, on the contrary, asserted that all the higher psychical processes, the intellectual as well as the conative, presuppose the existence of a plurality of simultaneous ideas in consciousness. Bonnet’s observa- tions are significant also for the distinction drawn by him between the range of consciousness and the range of atten- tion. In the visual field, for instance, a large part of the contents of focalized consciousness shows an approximately even distribution of clearness . 1 For the determination of 1 Essai de Psychologie, 1755, chap. XXXVIII. 184 HISTORY OF PSYCHOLOGY the range of attention Bonnet depended upon the same method which had earlier led Locke to assert the impos- sibility of imagining a chiliahedron. He stated it as a constant of visual imagination that only five or six s im ple contents, like the sides of a geometrical figure, could be grasped simultaneously with a maximum of attention. The first attempts at an experimental, quantitative de- termination of the range of consciousness were made by Sir William Hamilton . 1 Hamilton sought to ascertain how many instantaneously presented visual stimuli could be grasped at once, evidently proceeding on the assumption that the range of consciousness could be determined by simply counting the objects, like balls, for instance, which had been momentarily exposed. It was not until much later that it became clear that what Hamilton was investi- gating was not the range of consciousness but the range of attention. Hamilton’s constant, meanwhile, which never exceeded six impressions, has not only not been modified by later investigations, but it approximates also the earlier results obtained by purely introspective methods, in spite of the fact that the conditions of Hamilton’s investiga- tions were very different from those of Bonnet’s, since in Hamilton’s experiments a degree of consciousness sufficient for reproduction had to be attained, while Bonnet sought to ascertain the greatest possible range of simultaneously presented ideational contents. 4. The Graduation of Consciousness: Attention One of the most general characteristics of consciousness is described by the fact that within the field of conscious contents as a whole a narrower circle of so-called contents of consciousness rises into comparative prominence. The 1 Lectures on Metaphysics and Logic , I, p. 254. THE SUBJECT-MATTER OF PSYCHOLOGY 185 graduation of consciousness according to degrees of clear- ness was already a familiar aspect of the concept of con- sciousness in Leibniz, and the genesis of the notion of de- grees of clearness in the Leibnizian psychology has already received some attention in previous pages . 1 The relation existing between the fluctuation of attention and the clear- ness of conscious contents was also presupposed in the ear- lier efforts to construct a theory of psychical mechanics. It was Herbart who, starting with the conception of a competition among ideas and refining upon the Leibniz- ian terminology, designated the ideas showing the greatest amount of clearness by the general name of apperception. A new point of departure for the consideration of the problem of attention grew out of the connection of the problem of attention with that of abstraction, a connection which maintained itself for many centuries in the form of the so-called empirical theories of abstraction. In contrast with the antiquity of the problem of abstraction, which goes back to the early beginnings of the doctrine of general ideas, attempts to give a psychological account of abstrac- tion belong to comparatively recent times . 2 Oddly enough, we meet with them in a work conceived in the spirit of Cartesian rationalism, the Logique de Port-Royal . 3 The distinction is here made between the abstract and the general. The abstraction made in connection with a single object is a preparatory step toward generalization proper. On account of the circumscribed scope of consciousness it is able to grasp a complex object only by viewing separately the various sides which the object presents. This isolation of the separate sides of the object through abstraction is thus characteristically brought into connection with the 1 See p. 171, above. 2 Cf. K. Mittenzwey, in Wundt, Psychologische Studien, II, 1907, p. 358. 3 L’art de penser, 1662. Edit. nouv. par Fouille, 1879. 186 HISTORY OF PSYCHOLOGY narrowness of consciousness. Great as was Locke’s sub- sequent contribution to the description of the processes of abstraction, he never succeeded in giving a psychological explanation of the activities in question. It is true that he specially mentioned the fact (to use his own illustration) that the mind observes the same color in chalk or snow to-day that it yesterday received from milk. But the rea- son for this he never gave . 1 A purely empirical solution of the problem as to the manner in which this abstraction takes place was given by Hume. When we distinguish the form of a body from its color we view the body from the different points of view which result from the different se- ries of resemblances into which the characteristics observed arrange themselves . 2 With this the problem of abstraction was solved to the extent that the older question of generali- zation gave way to that of abstraction in the case of the sin- gle presentation. The nature of this process of abstraction, however, reduced itself again in Hume to the play of the mechanism of association. A new phase of the problem, developed in contemporary French psychology, brought the process of abstraction into relation with that of attention. The idea that attention isolates a given sense quality from the rest, thus resulting in abstraction, goes back to Condillac. In its essential features this view was still represented, at the beginning of the nineteenth century, by Laromiguiere . 3 More important were the attempts of Bonnet to make an analysis of the process of attention, although he still depended largely upon the ideas of the nerve-fibre psychol- ogy . 4 The distinction between sensation and reflection as two different sources of ideas Bonnet derived from the psy- 1 An Essay on the Human Understanding, II, chap. XI, p. 9. 2 Treatise of Human Nature, I, § VII. 3 Logons de philosophic, II, 3d ed., 1823, p. 321. i Gf. p. 94, above. THE SUBJECT-MATTER OF PSYCHOLOGY 187 chology of his time. The ideas of reflection arise in conse- quence of the action of attention upon the nerve-fibres with which the ideas in question are associated. That true perception arises only in this way Bonnet illustrates by the example of a preoccupied philosopher who is taking a walk through the woods. Most of the impressions from his sur- roundings glide over the surface of his consciousness, only those attracting the attention which are important for his welfare . 1 Bonnet’s theory of abstraction, with its emphasis upon attention, has in its main features served as a model for many other treatments of the subject. In Germany, Lossius interpreted it in a peculiar manner in terms of physiological processes . 2 Since the soul is unable to think without the action of nerve-fibres, even general concepts must have physiological correlates. In three partially identical presentations, Am, An, and Ap, A is represented by a common nerve-fibre. If this is excited alone, the result is a general idea common to all three presentations. Through such reinterpretations the empirical theory of abstraction became pretty far removed from the psycho- logical problem of attention. The insight into the connec- tion between the isolation of mental contents accomplished through attention and the distribution of degrees of clear- ness was reserved for English psychology. We meet it in the turn which Hamilton gave to the problem of abstraction. Whether considerations of this kind had any significance for the logical side of the problem of abstraction is not im- portant here. What is of importance for the doctrine of attention is the process of abstraction in the sense of the isolation of the contents observed, and Hamilton located the central point of the problem by bringing it into relation to the circumscribed scope of consciousness. Since atten- 1 Cf. J. Speck, Arch. f. Gesch. d. Phil., XI, 1898, p. 181. 2 Physische Ursachen des Wahren, pp. 156 ff. 188 HISTORY OF PSYCHOLOGY tion can grasp only a small number of impressions simul- taneously, and these only imperfectly, the turning of the attention toward a given impression means the withdrawal of it from the rest . 1 Meanwhile, attention is described as a will act conforming to a definite psychological law, the law, namely, that the greater the number of impressions simul- taneously presented to consciousness the less the intensity with which each of the separate impressions is felt. Atten- tion was thus recognized as consciousness of a higher degree or strength. It is true that we still have an identifica- tion of the range of attention with that of consciousness . 2 Nevertheless, the two characteristics which Hamilton found in the experience of attention, namely, the increased clear- ness which attention involves and the close relation of at- tention to will, have been incorporated into the modern concept of attention as its most important characteristics. Freed from its long entanglement with the problem of abstraction, the concept of attention or apperception has become one of the fundamental concepts of psychology, illustrating not only an elementary aspect of consciousness but the simplest form of conation as well. To what extent experimental methods have entered this field is illustrated by the work of W. Wirth, whose exper- imental investigations were based on the thought that an exact determination of degrees of consciousness could be obtained from the apperceptively conditioned changes in psychical magnitudes, such, for example, as a difference- threshold. The most important result of the evolution of the con- cept of consciousness as a whole is the extension of the narrower connotation of consciousness as inner awareness to include the whole phenomenological constitution of the 1 Lectures on Meta-physics and Logic, 5th ed., 1870, p. 258. 2 Cf. p. 184.' THE SUBJECT-MATTER OF PSYCHOLOGY 189 ego, or the totality of psychical experiences. In this way the concept of experience was extended beyond its original meaning as the inwardly perceived so as to include what the ego actually constructs. The difficulty, however, that the ego of pure apperception in the Kantian sense, as the locus of relations for all conscious contents, cannot itself be a conscious content standing on a level with other contents has given rise to serious misgivings . 1 This difficulty has only recently led Natorp to argue that consciousness means object for an ego and that this object relation cannot again become an object. In order to solve this difficulty, a num- ber of psychologists have suggested a new definition of con- sciousness according to which consciousness is a general term for psychical activities . 2 Now, these activities can be directed upon the phenomenological ego just as w 7 ell as upon other objects. This shift in the meaning of the concept of consciousness wdiich the purely descriptive efforts of these psychologists effected brings us to the subject of the clas- sification of the contents of consciousness. 1 Cf. p. 179, above. 2 E. Husserl, Logische Untersuchungen, II, p. 342. CHAPTER YII CLASSIFICATION OF THE CONTENTS OF CONSCIOUSNESS Attempts to classify psychical phenomena according to their chief differences arose at a much earlier period than the formation of a concept which would express their com- mon characteristic, namely the concept of consciousness. The differences in the content of consciousness forced them- selves on the attention first of all, long before their common participation in one unified conscious existence was noticed. The older classifications were, therefore, not made on the same basis as the later ones. For these latter were based upon characteristics which only appear when the separate psychical contents are regarded as being contents of con- sciousness belonging to one whole. Nevertheless, the striv- ing toward an appropriate classification of the contents of consciousness has always been in psychology the sign for the rise of empirical thought. The individual classifications of varying extent with which psychology busied itself are subordinate to the problem of a general classification of the contents of con- sciousness, which deals with the highest classes or genera of the contents of consciousness. Now, if a classification is built upon ideas of similarity, it generally becomes am- biguous, since each content of consciousness may be grouped differently according to different ideas of similarity. What determines the grouping is the choice of a definite principle of classification. We can, therefore, best orient ourselves by means of a survey of the most important principles of 190 THE CONTENTS OF CONSCIOUSNESS 191 classification upon which in the history of our subject the attempts at classification have been based. Many of these principles are still exerting their influence at the present day. This is especially the case with that principle out of which the concept of a psychical element has arisen — a concept that has been so important in modern classifica- tions. i. Survey of the Most Important Principles of Classification Before the application of empirical principles of classi- fication we find many primitive attempts to do justice to the diversity of psychical facts. The metaphysical psy- chology, to which the problem of classification was really foreign, was inclined most often to dispose of it by presup- posing different substrata for the phenomena. In the theory of the divisions of the soul, the necessity for classi- fication finds a naive expression, inasmuch as the principle of unity in regard to the experiences of each such division of the soul is maintained . 1 The empirical classifications can be arranged under three heads. Most often the principle of non-derivability has been used, according to which the highest classes were formed of contents of consciousness which could not be derived from each other. Under this head comes also the differentiation of the contents according to their origin, in so far as their non-derivability is an immediate consequence of the difference of their origin. Not so openly acknowl- edged and, therefore, more often unconsciously effective, is the principle of intentional relationship, by means of which the fundamental divisions are made according to the way in which the contents of consciousness are related to 1 Cf. p. 46. 192 HISTORY OF PSYCHOLOGY their intentional object. Superior to these two principles is, lastly, the principle of analysis, which takes as its point of departure the division of all contents of consciousness into complex and simple. (a) The Rise of Psychological Classification The division of conscious experiences was suggested in the first instance by expressions used in speech. For a long time this motive for classification escaped psychological analysis, as is seen in the ramifications of the old faculty psychology. In the earliest divisions of metaphysical psy- chology we note that here also non-scientific points of view dominate, mostly in the form of analogies with principles of division that man had employed upon the things of his environment. The threefold division is an ancient pos- session of mankind. Even the Indian theory of the soul mentions three kinds of psychical content: (1) Guna, or spirit, also called satva (sense of truth) or atman (breath); (2) radschas or manas (energy), also called ahankara (feel- ing of self); (3) tamas (darkness), as the symbol of pas- sion or desire. This threefold division is a connecting-link in a long chain of analogy, which begins with the three gods, Indra, Varuna, and Agni, is continued in the three elements of nature — light, air, and earth — and which ulti- mately terminates in the threefold division of society into Brahmans, or priests; Kschatrijas, or warriors; and Vaigjas, or workers. Similarly the twofold division into higher and lower functions of the soul corresponds to the pairs of oppo- site words found almost in every language, as in Hebrew ruach and nephesch, in Greek wfi? and tyoxv, in Latin animus and anima, and in Slavonic languages duch and duse. 1 In the older divisions of Greek psychology ethical considera- 1 0. Willmann, Empirische Psychologie, 1904, pp. 11 ff. THE CONTENTS OF CONSCIOUSNESS 193 tions join with these language influences and help determine the division. Plato’s division was based upon the two chief differences in the direction of moral strife and expressed clearly the conflict between the demands of reason and those of the sensual desires in man. The classifications of Aristotle are the first that begin to show some understanding of the peculiar nature of psychic content. Of his principles of division, that one has most psychological importance according to which he divides psychical activities in relation to their object. In Scholas- tic terms, it is the method of intentional in-existence that causes the difference between thinking and desiring. These two activities are not directed toward different objects but toward the same object in a different manner. The same thing may be at once object of thought and of desire . 1 The decisive characteristic is no longer the difference in the substratum, or bearer, but rather the relation to the inten- tional object. With this we see the foundation of a prin- ciple of differentiation that has been dominant for many centuries. The ideational and the volitional worlds were in this way empirically separated. The effect of this point of view of intentional relationship is seen in the fact that that group of experiences which do not so readily show such a relation- ship, i. e., the feelings, were neglected in this classification, and only very much later were they recognized as a special psychical division. We owe the first thoroughgoing psy- chological description of the affective experiences to Augus- tine. Influenced probably by his own enhanced affective life, he grouped the feelings in an independent division alongside of ideas and will . 2 In the Middle Ages, however, 1 Be Anima, III, 10; Metaphysics , XII, 7. 2 Cf. Siebeck, Beitrage zur Entstehungsgeschichte der neueren Psycho- logic, Giessen, 1871. 194 HISTORY OF PSYCHOLOGY these beginnings were lost sight of because of the dominance of the Aristotelian twofold division. In Thomas Aquinas’s famous theory of the emotions we find simply the tradi- tional opinion that feeling is only a modification of desir- ing. A separation of the feelings from the volitional proc- esses begins first of all with Duns Scotus, who classed pleasure and pain as “passions,” and differentiated them from acts of will. The speculations of the German mystical philosophers arrived in quite a different fashion at an understanding of the affective processes. It is true that these mystics had a great many problems in common with Scholastic philosophy, but they experienced these problems differently. Master Eckhart started with the discussion whether the will or the intellect was the superior power, and he settled this in his own peculiar fashion by lapsing into an emotional state beyond will and intellect in which both of the latter coalesced into one unity. Since Scholastic philosophy had no expression for such experiences, he coined the word Gemiit. 1 This was the signal for the further naming and emphasizing of the affective experiences. It was a long time, however, before scientific psychology was at all influ- enced by these important presentiments of the pious mystics. ( b ) The Principle of Non-Derivability The new concept of consciousness made possible the con- ception of psychical phenomena as belonging to an inde- pendent field of experience, and from this conception there arose a number of different points of view for purposes of classification. Only after consciousness had been found to be a common characteristic of psychical contents could 1 [“Feeling and Will; the Sum Total of Affective-Conative Processes,” Titchener, Am. J. of Psych., VII, p. 81. Trs.] THE CONTENTS OF CONSCIOUSNESS 195 the content of consciousness be classified according to purely phenomenological attributes. This new standpoint is clearly seen in Locke’s classification of the contents of conscious- ness. Locke first of all divided his “ideas,” which coincide with our modern conception of the contents of consciousness, into complex and simple, and classified the latter accord- ing to their origin, that is to say, according to the manner in which they enter into consciousness. This principle of classification naturally came to him because he had pre- supposed that the mind was at first absolutely blank, a tabula rasa. In this manner he arrived at the following four classes: 1 (1) Ideas that come into the mind by one sense only (simple sensations) ; (2) ideas that come into the mind by more senses than one (e. g., extension, form); (3) ideas that are to be had only from reflection or introspection (thinking and willing); (4) ideas that are suggested to the mind by all the ways of reflection and sensation (e. g., plea- sure, existence, energy, time). The greatest misgivings arise, of course, in regard to the last class. The differentiation between ideas of reflection and those that enter the mind by means of sensation points forward to the later differentiation between the subjective and objective sides of consciousness. Again, Locke’s method of first considering the simple ideas became common in much of the psychology from his day onward. His simple ideas are already elements in the sense that they can neither be produced nor destroyed by the mind. They are things given to us in experience, and when this is not the case they cannot be produced by any power of even the most sublime genius. 2 We must also remember that the different origin of these classes of ideas brings with it their reciprocal non- 1 Essay on the Human Understanding, II, chap. Ill, § 1. 2 Op. cit., chap. II, § 2. 196 HISTORY OF PSYCHOLOGY derivability, which is caused by the simple character of these ideas. We find, therefore, in Locke the origins of the most important points of view which have been used in later psychological classifications. Nevertheless, in spite of all this, the old Aristotelian two- fold division into thinking and willing continued to exist for a long time. It was, in fact, the chief ground of division in the psychology of Wolff, who also used, in addition to this, the popular division into higher and lower activities of the soul. In English psychology Hume continued the two- fold division, and it was retained right down to the time of Reid and Brown. The latter subordinated it, however, to the division of all content into outer and inner affections: the first class comprised all sense-perceptions, and the second contained intellectual mental states and affective states (moral phenomena). It was not until the psychology of the German Enlighten- ment that a new terminology came into being. In Tetens and Mendelssohn 1 feeling is recognized as a third class alongside of intellectual and volitional processes. Tetens separates sensation and feeling clearly, inasmuch as he explains the former as a copy of the object and the latter as a change in the perceiving subject . 2 A more thoroughgoing foundation for the division into knowing, feeling, and willing is found in Kant, especially in his treatise entitled Uber Philosophic uberhaupt, which gives the best summary of his general psychological views. These classes, he maintains, are fundamental for the rea- son that they are neither derived from each other nor can any one be traced back to the other. Such a method of reasoning was peculiarly adapted to the old faculty psy- chology, because the phenomena, the sum total of which 1 Gesammelle Schriften, II, p. 295. 2 Philosophische Versuche, I, pp. 214/. THE CONTENTS OF CONSCIOUSNESS 197 went to form such a class, were considered a 'priori as effects of a single faculty and, as such, had to resemble each other to a very great extent. The faculties themselves, however, had to be independent and absolutely heterogeneous if dif- ferences in mental life found in our inner experience were to be explained by their activity. In so far as the discussion of this division was carried on in the Kantian school from the standpoint of the faculty psychology it loses interest for us. Krug, for example, maintained that only two faculties were necessary, namely, ideation and endeavor, because the activity of the human mind was exerted in two directions — outward and inward. It was Hamilton, however, who gave a more serious vindi- cation of the Kantian classification. He strove to justify the position that feeling should be considered as an inde- pendent class, since there exist states of consciousness that cannot be classified as belonging either to thought or to active endeavor . 1 In spite of this co-ordination of the three classes there remained, nevertheless, an order of prece- dence, in which knowing took the first place. For, if we consider which one of the three classes is least dependent on the others, it is at once clear that knowing is the only one that could lay claim to be an independent entity. In the second place comes feeling, which can at least be thought of as taking place without volitional processes. The re- maining class always presupposes the co-operation of the two others . 2 After Herbart’s attempt to abolish all multiplicity of men- tal faculties it was Lotze who was most pronounced in his defense of the Kantian threefold division. He did not wish or attempt to support that strict division which regarded knowing, feeling, and willing as three lines of development 1 Lectures on Metaphysics, II, p. 423. 2 Op. cit., I, p. 187; II, p. 431. 198 HISTORY OF PSYCHOLOGY absolutely independent of each other. In comparing mental phenomena, however, he was driven to make the hypothesis that, in the dependence of experiences of these different classes on each other, the first process acts as a kind of inducing motive to the succeeding process, but does not cause it, while at the same time there is some power or force at work which gives its assistance, but which escapes our observation. If the soul were nothing else than a think- ing or imagining being, there would be no sufficient reason why anything else except this special activity should be called into being. There would be no reason for feelings of pleasure and pain. Any inner change, however dan- gerous it might be for the soul’s own existence, would sim- ply be observed or perceived by it, just as it simply observes any other conflict of forces . 1 This description of Lotze is worthy of note because it is an attempt to give a purely psychological foundation to the fundamental thought un- derlying the Kantian threefold division. There is another form of the threefold classification that uses for its general principle of classification the pop- ular psychological distinction between actual sense-impres- sions and their reproduction or mental images. This is not met with so often in the history of psychology, al- though just such a threefold division, which regards as ultimate elements sensations, images, and feelings, is to be observed in modern psychology . 2 If we pass over the primitive explanation which was satisfied with the old theory of the inner sense, inasmuch as it referred the differences between sensations and their reproductions to the outer and inner senses , 3 we see at once that this question was not of special importance for faculty psychology, because it was presupposed that the soul had an immediate conscious- ness of its different activities. Locke w T as content merely 1 Mikrokosmos, I, pp. 193 ff. 2 See below, 2. 3 Cf. pp. 71 /. THE CONTENTS OF CONSCIOUSNESS 199 to affirm that the soul was passive in sensation and active in reproduction. This same opposition occurs again in Leibniz , 1 who regarded sensation as passive, because of its vagueness, and the image or thought process as active. Purely psychological characteristics for such a differen- tiation were first sought by the English Sensationalists. It is obvious that motives prompted by their theory of knowledge led them to fix upon a clear distinction between sensation and the reproduction of sensation. Berkeley had already noted a long list of criteria that distinguished sensations from images: intensity, vivacity, duration, and orderly coherence . 2 And Hume also attempted in different ways to make it clear why it is that we experience mental images as different from sensations. He found, for example, that the most vivid reproduction is clearly inferior to the most vague sensation. This is an opinion that Spencer repeated a hundred years later . 3 French Sensationalism did not make the distinctions quite so fine, for, following the example of Condillac , 4 the difference between vivacity and intensity was neglected, and the two were considered identical. Alongside of this purely psychological determi- nation of the difference, there have always arisen attempts at a physiological explanation. Hartley translated Hume’s description into the language of his vibration hypothesis, and he gave it the interpretation that the breadth of the oscillation of a sensation always exceeded the breadth of the oscillation of the reproduction. When such a naive, materialistic explanation was no longer tenable, the oppo- sition between the sensory and motor nervous systems was made use of, as, for example, in the writings of George, who took into account the physiological knowledge of the nineteenth century. 1 Monadologie, 49. 2 Treatise, 30. 3 Principles of Psychology, I, § 49. 4 Traite des sensations, I, 2, 9. 200 HISTORY OF PSYCHOLOGY The problem as to the relation between sensation and reproduction is solved at last in the simplest manner by means of the presuppositions of Herbart’s psychology. Here they turn out to be simply different periods in the history of the same idea. Sensation is the idea from its development to its first disappearance, and reproduction is the idea from its reappearance in consciousness to its next disappearance . 1 Under these circumstances there was no decisive motive that might lead to a division of sensation and image into two absolutely independent classes. We see, therefore, that the most universally acknowledged consequence of the principle of non-derivability is the threefold division into feeling, willing, and thinking. (c) The Principle of Intentional Relationship The principle of non-derivability was subjected to the keenest criticism by Brentano , 2 even though we can trace back to him many of the principles mentioned above. If two psychical phenomena are to be looked upon as belong- ing to absolutely different classes, simply because we cannot a priori draw a conclusion from our capacity for the one to our capacity for the other, we must not only, along with Kant, Hamilton, and Lotze, separate thinking from feeling and desiring but also seeing from tasting. Why, we must even go further and separate red vision from blue vision as from a phenomenon that belongs to another ultimate class. In fact, if we look closely, we see in those thinkers the unconscious influence of the characteristic of intentional in-existence used by Aristotle in his classification. Kant makes the distinction between knowing and desir- 1 For this description see Volkmann, Lehrbuch der Psychologie, I, § 80. 2 Psychologie vom empirischen Standpunkte, I, pp. 246 ff. THE CONTENTS OF CONSCIOUSNESS 201 mg consist of a difference in their relation to the object; and the peculiarity of feeling is supposed to be due to the fact that in this case merely a relation to the subject exists. Reciprocal non-derivability follows as a necessary conse- quence of this difference in intentional relation; but not in all cases of non-derivability need the intentional relation be of another kind. This latter principle of classification is, therefore, superior to the other. We find the same opinion in Hamilton. In the phenomenon of knowing, consciousness distinguishes between a known object and a knowing subject; in the case of the feelings, however, con- sciousness is itself fused with the psychical state. And, lastly, in the case of desiring or willing there is, just as with knowing, a relation to an object, but knowing and desiring are differentiated just by the difference in their relation to the object. This last point of view seems to have been decisive for Hamilton. The man who most thoroughly fol- lowed out the consequences of this principle of the non- derivability of faculties was Lotze, and he was roused to do this by the polemic against Herbart. He did not draw back from the logical consequences, for he maintained, for example, that the faculties of seeing and hearing were different, original, and independent faculties . 1 And yet, since he classed the images of tones and colors in the same class, it would seem as though another point of view had been at work in his division into three classes. In place of the principle of non-derivability, Brentano, therefore, took the principle of intentional relations in order to determine the chief classes of mental phenomena. He found in accordance with the different ways of intentional in-existence three main classes — ideation, judgment, and emotion. He vindicated this division by appealing to inner experience, and held that within the same class the relation 1 Mikrokosmos, I, p. 198. 202 HISTORY OF PSYCHOLOGY of consciousness to the object is always the same or sim- ilar, whereas between the classes this relation is essentially different. For the separation of ideation and judgment, which is the most surprising thing in this new threefold division, Brentano gave an indirect proof. If no such fundamental difference in their intentional relations existed, then the difference must lie either in the content, to which they both refer, or in the degree of perfection, in which the same content may exist in our minds as ideation or as judg- ment. Since, however, neither of these is the case, the difference can only be one of intentional relation. This threefold division is connected in a peculiar man- ner with Brentano’s theory of the inner consciousness. Each psychical act, however simple, can be looked upon as idea of itself, as knowledge of itself, and as feeling of itself. In this we see clearly Brentano’s striving to make the three kinds of intentional relationship the necessary forms by means of which anything comes to consciousness and thereby give his three chief classes a logical connection in conscious life. To thoroughly appreciate this classifica- tion, one must remember his concept of the “psychical phenomenon” 1 in which the use of this principle of inten- tional relation is obviously foreshadowed. Besides this, the use of this principle gave his logical tendencies plenty of scope, inasmuch as the most important function of logical thinking, i. e., judgment, became one of the fundamental classes of the mental processes. (d) The Principle of Analysis When we call to mind how comparatively late in the history of psychology any reflection as to the conditions of psychological analysis arose, we cannot be at all surprised 1 Cf. p. 84. THE CONTENTS OF CONSCIOUSNESS 203 that the distinction between simple and complex contents of consciousness is of recent origin. Along with this there are the peculiar terminological difficulties with which psy- chology has had to contend from the very beginning. Ex- pressions denoting complex processes, such as idea, emotion, etc., become fixed in a language long before those denoting the simple processes. It was Wolff, in Germany, who helped to make general the word “ Vorstellung” as an equivalent of the English word “idea.” The German word “Gemiit” comes from the original stem “mut,” and was used for a long time and even by Kant as synonymous with “ Seele” or “ Bewusstsein.” The mystic philosophers gave it a dif- ferent and peculiar meaning which we have noticed before . 1 Of a much later date is the differentiation between the simple contents of consciousness, which in our modern terminology we are accustomed to separate as sensation and feeling. From the seventeenth century onward the two words were used almost synonymously. In the philosophy of the Romantic period and afterward we begin to note an ambiguity of meaning, for, on the one hand, feelings, as the most immediately experienced subjective states, stand in a kind of opposition to the peripherally conditioned sensations; while, on the other hand, especially among the physiologists, the feelings are restricted to certain kinds of sensation, e. g., the sensations of the skin, the organic sensations, etc. The principle of division into simple and complex con- tents of consciousness, bequeathed by John Locke, has remained one of the common characteristics of English psychology. And yet even in England the threefold di- vision was in a way retained by Lewes, who supported it with a doubtful analogy between the psychological spec- trum and the optical spectrum. The three principal colors 1 Cf. p. 194. 204 HISTORY OF PSYCHOLOGY led on the psychological side to a threefold division into sensation, thought, and movement ( sensation , ycnsee, mouvement ) , and the first of these depended upon sensorial, the second upon cerebral, and the third upon muscle energy. Bain also accepted the threefold division into thinking, feeling, and doing . 1 But, alongside of this, he set up the more important division of psychical phenomena into primitive and such as developed out of the primitive. It was Spencer, however, who was the first to carry out this evolutionary principle thoroughly. The mental activities of the developed consciousness fall into two groups— cog- nitive (memory, reason) and affective (feeling, will). The simple contents of consciousness, which in Spencer’s termi- nology are designated “feelings,” can be separated into emo- tions, which belong to the centre of consciousness, and into sensations, which belong to the periphery of consciousness. This division is supported by a second division, which, tak- ing an analytic point of view, separates the feelings from such parts of consciousness as can be called, in general, relations between feelings. A “feeling” represents any part of consciousness, which is an individual entity marked off from the neighboring parts of consciousness by qualita- tive differences and which to introspection appears homo- geneous. A “relation,” on the other hand, is not taken up with any perceptible part of consciousness. It disappears at once along with the elements if one abstracts from these. A second essential difference between these two kinds of conscious experiences consists in the fact that a feeling of relationship cannot be analyzed into parts, whereas an ordinary feeling permits at least of an imaginary analysis into similar parts. These ideas were influential in forming the concept of the psychical element, a concept which has been decisive 1 The Senses and the Intellect, p. 2. THE CONTENTS OF CONSCIOUSNESS 205 in modern forms of classification, although even here the older principles in many cases still exert their influence. 2. Modern Forms of Classification The differentiation of complex and simple contents of consciousness has been decisive in different ways for the classifications of modern psychology. Many attempts start with the idea of finding principles of opposition which will be equally binding for complex and for simple contents. Here belongs the psychology of Lipps, who set up a number of such principal oppositions. The first of these oppositions is that between experiences of the ego and conscious ex- periences which are not experiences of the ego; alongside stand the no less fundamental oppositions between act and receptive experience, and between act and activity. These oppositions, and especially the first of them, show a certain relationship to the distinction between subjective and objective contents of consciousness, although this latter division is much more consciously dependent upon pre- suppositions derived from the theory of knowledge. Husserl went back to the researches of Brentano in regard to intentionality. By separating the experiences of con- sciousness into acts, i. e., intentional experiences, and not- acts, he arrived at a type of classification to which the fundamental oppositions set up by Lipps would have led. The position to which Husserl relegates the feelings is, how- ever, peculiar. The separation of all conscious experiences into intentional and non-intentional would be merely an external point of view if experiences of the same descrip- tive genus showed at times intentional relation to an object and at other times no such relation. At the first glance such a state of affairs seems actually to exist in relation to the class ordinarily called feelings. Undoubtedly, there are intentional feelings, e. g., joy in a certain thing. As exam- 206 HISTORY OF PSYCHOLOGY pies of non-intentional feelings, it is usual to mention the sensational feelings, e. g., the pain of a burn on the skin, the pleasurable taste of a certain food. The difficulty can be solved by maintaining that these “feelings” do not be- long to the same descriptive class as those of pleasure and displeasure. And, accordingly, Husserl divides the totality of feelings into affective sensations and affective acts. This solution of the riddle of the feelings by means of the division of experiences into sensations and acts, i. e., into two dif- ferent classes, is seen also in other proposals for a method of classification. We see it, for example, in Stumpf , 1 who reckons the sensational feelings as affective sensations and classifies them along with the sensations. Jodi 2 tried in a circumspect manner to bring the old threefold classification of feeling, willing, and thinking into line with modern ideas. Conscious activity is neither cognition alone nor volition alone nor feeling alone; it is rather the combination of the spontaneity and receptivity of an organic being. We should, therefore, no longer seek for separate kinds of activities, for it is rather the case of a single psychical activity appearing in various aspects. Just here lies the chief difference of a classification in the mod- ern sense, in contrast to the older standpoint of the fac- ulty psychology. Jodi finds in every psychological activity three such moments — the impression from without working inward; the response from within working outward; and an inner connection between these two links of the chain. Thus result sense-impressions, feelings, and volitional ten- dencies as the three chief kinds of conscious reaction of or- ganic beings to the impressions of the surrounding world. If we turn aside from this attempt to find the fundamental classes that are necessarily connected with conscious reaction, 1 “ tJber Gefuhlsempfmdungen,” in Zeitschr. fiir Psychologie, Band XLIV, 1907, p. 1. 2 Lehrbuch der Psychologie, 1896, p. 130. THE CONTENTS OF CONSCIOUSNESS 207 there yet remains the possibility of grouping the elementary contents from the point of view of our direct experience of them. According to this principle, Ebbinghaus 1 arrived also at a threefold division of psychical contents; but he took as the fundamentally different classes of experience sensations, images, and feelings. This point of view of the immediately perceived differences in the kinds of experience would seem at the first glance to lead necessarily to a per- fectly uniform and unambiguous classification. Strangely enough, however, it has given rise to very different ultimate classes. The fundamental distinction between sensations and their reproductions or images has been questioned, and questioned by a classification that also appeals to imme- diate experience and decides upon a twofold classification of the contents of consciousness. In Wundt’s psychology sensations and feelings form the two classes of elementary contents, a division which agrees with the fact that imme- diate experience contains two factors — an objective content of experience and the experiencing subject. In contradistinction to all other attempts at classifica- tion, the theory that there are two principal kinds of ele- ments in consciousness, the subjective and the objective, rests upon the universal fact of consciousness that the imaging subject can distinguish or differentiate itself from its images. If this principle of division is acknowledged there arise further questions as to the relation in which these different kinds of elements may stand. Would it be conceivable that psychological analysis should lead to the discovery of a greater number of elements? If we are deal- ing solely with empirically given elements, then it must be possible to conceive of a greater number of elements, just as it is possible to conceive of a greater number of color sensations than those contained in the color circle. Such 1 Grundzuge der Psychologie, I, 1902, pp. 167 /. 208 HISTORY OF PSYCHOLOGY color sensations cannot be represented in a concrete ( an - schaulich ) manner, but they are thinkable exactly in the same sense as any abstract {unanschaulicli ) multiplicity is, e. g., space in more than three dimensions. The two- fold division of conscious experiences into subjective and objective seems to be a perfectly unique kind of division. It has often been shown that sensations and feelings cannot as independent component parts fuse together into one whole called conscious experience. And the opposite opin- ions that those classes are nothing else than characteristics or different sides of the same conscious experience, leads into great difficulties in facing the problem of making clear this union of the subjective and objective sides of conscious- ness. As an analogy the union of the intensity and quality of a tone might be made use of. But these two character- istics have a bearer, or substratum, namely, the tone. Whether consciousness could be in this sense considered the substratum of feeling and sensation remains yet to be settled. Possibly the combination which the elements of consciousness form together is just as inconceivable (un- anschaulich) as the combination of a real and imaginary number into one complex number, a bi. The discussion of this position throws a new light upon those attempts which aimed at finding one single class of psychical elements. This they achieved in considering sen- sations as the most readily isolated component parts of conscious life. The historical background of this line of thought is formed by the intellectualism of Herbart, who recognized only simple ideas and identified these abso- lutely with sensations. In recent years Miinsterberg 1 has modified this theory in a surprising manner. He starts out from the standpoint of method, from the possibility of the communication of psychical contents. The two com- 1 Grundzuge der Psychologie, I, 1900, p. 309. THE CONTENTS OF CONSCIOUSNESS 209 munications that it is raining outside and that I am happy are from the point of view of method absolutely distinct. The first case of outer sense-impression can be explained by direct description of the content of conscious- ness; but in regard to the latter I can never really tell if that which the other calls a feeling of joy may not be what I call anger. Psychology has therefore to resort to indirect description, and it does this by considering the total content of consciousness as a combination of elements which in the images of sense-impressions show noetical relations to the physical world. Such elements are, however, nothing else than sensations. If two sensations are similar to each other we are driven to the conclusion that each of them is divided into parts, some of which are common to them both. Now, since each sensation shows some similarity with some other and is never unique, it therefore follows that no sensa- tion represents a psychological atom and that each is com- posed of elementary component parts. These thoughts lead to an atomic theory of consciousness which goes far beyond the claim of sensation to be recognized as a psychi- cal element which is not further divisible. They lead us to seek the true elements of psychical life beyond sensation. Of course, Miinsterberg cannot maintain that psychical processes are in absolute reality nothing but sensations; he admits they are unities, but in our analysis of them we may arrange them in some new form. Thus an image is made up of elements in the sense that there is a special logical value in the notion of an image as being a combina- tion of elements. All these modern forms of classification have started with the principle of analysis, and they have ended logically in the problem of the psychical element, and, as we have seen, this element has changed its role very often in the classifi- cations we have described. 210 HISTORY OF PSYCHOLOGY 3. The Concept of the Psychical Element The demands which led to the modern concept of the psychical element are in direct opposition both to the tra- ditional faculty psychology and to the more recent conten- tion that a simple content of consciousness, as, for example, the simple idea of Herbart, can exist in and for itself. Much rather are we to conceive of the parts of our continuous psychical experience as incessantly entering into all kinds of relations with one another. The elements, however, are what he beneath theses They cannot be further ana- lyzed, although they may appear in any combination. In this manner Wundt established the concept of the psychical element. In opposition to this, however, the de- scription of consciousness as “a stream of thought” was used. According to Dilthey 1 this continuous flow of the contents of consciousness forms an impediment to the use of any kind of “element” concept. A slight change in the concept is brought about when the elements are looked upon as mere artifices for the purposes of abstraction, and in this form the concept has been made the foundation of many popular presentations of psychology, as, for example, in the psychology of Rehnike .' 2 In the controversy over this concept an analogy between the physical and psychical atoms was often made use of, but this analogy fails precisely in the most important point . 3 The psychological elemen- tary concepts ought not to be compared with the analysis of matter into atoms, but rather with the analysis of a movement into its components or into the momentary velocities of a moving point. These are the only things 1 “Ideen uber eine beschreibende und zergliedemde Psychologie,” in Sitzungsbericht d. Berl. Akad., Xo. 53, 1S94. 2 J. Rehnike, ATlgemeine Psychologie, 1904. 3 Cf. Wundt, Grundz. d. physiolog. Psychol., I (6 Aufl.), 190S, p. 417. THE CONTENTS OF CONSCIOUSNESS 211 that would at all correspond in the department of physics. The continual change of conscious experiences hinders the determination of psychical elements just as little as a ve- locity changing from point to point hinders the determina- tion of the momentary velocity at any single one of these points. The question as to the kind and number of such elements becomes, then, a purely empirical one. Taking this position, psychology cuts itself completely loose from all the entice- ments of a metaphysic of consciousness, which sees in the classes of the content of consciousness the expression of ideal regularity according to law. This question of the psychical elements is not merely a question of a new group- ing of long-known contents of consciousness. In recent years we have seen how systematic introspection has led to the discovery of a class of experiences up till now totally disregarded, the so-called states of awareness , 1 which, ac- cording to the opinion of Ach, must be considered as an inde- pendent class along with the previously recognized classes. This explains, in a way, the difference of opinion which at present exists as to the number and nature of the psychical elements. Even though attempts at classification can be traced back to the oldest period of psychological thought, yet the problem of the psychical element implicit in them is the product of the last few years. 1 Cf. pp. 136/. CHAPTER VIII PSYCHOLOGICAL METHODS In the development of psychological methods, as in the development of the methods of any science, we can divide the methods into two kinds : those that procure a knowledge of the facts, i. e., the practical or working methods, and those that serve to work up special facts, i. e., the theoretical methods. Scarcely any other science has had those of the first kind ever questioned, but psychology has had to fight for their recognition. In the controversies as to the rela- tion between introspection and observation, theoretical view-points have mostly predominated. And the same is true of the attempts that arose from this; namely, to base psychology upon physiology. It was only the development of psychical methods of measurement that led to real working methods, which had as their aim exact and, as far as possible, quantitative results. i. Observation and Introspection That psychological facts are given only to our inner experience can never be seriously questioned. And there are many psychologists of the present day who are of the opinion that introspection alone is perfectly sufficient to obtain a knowledge of them. Scientific introspection is, of course, considered to be a special art, which is more full of content and more systematic than common intro- spection. The apparatus it makes use of is no other than 212 PSYCHOLOGICAL METHODS 213 / that which always stands and has always stood within the reach of every man. It becomes more and more refined in proportion as the conscious life itself becomes richer and more varied, but a real history of these methods can scarcely be said to exist. It is possible that the irregular course of the history of psychology, interrupted by so many leaps and bounds, may have something to do with this peculiarity of introspection. The continuity of psychological thought has often been broken. How often a pre-Raphaelite return to long-for- gotten forms of thought has followed a period of the keenest hopes and anticipations! Is not the fact that each single individual, by means of his introspections, has access to all psychical phenomena a temptation and an urgent motive to begin all over again from the very first? Certainly the theory of the inner sense, which arises in a certain historical relation with introspection, busied itself with the peculiar- ities of introspection. But this did not result in a develop- ment of the achievements of introspection, but only, on the one hand, in a kind of hinting in a fantastic way at such possibilities, and, on the other hand, in drawing a distinc- tion between the methods of introspection and those of the so-called outer observation. Even though we may acknowledge that introspection is the presupposition of every psychology, nevertheless introspection was by no means the beginning of scientific psychology. It is through nature that man has not only got to know himself but has also learned to observe himself . 1 It is no mere chance that the first psychological knowledge among the Greeks comes from mathematicians and physi- cists. Of course it is true that many universally valid facts of human psychical life appear also in mythological ideas and in the concrete expressions of such in art. But it 1 Cf. H. Ebbinghaus, Kultur der Gegenwart, I, 6, 1908, pp. 175 ff. 214 HISTORY OF PSYCHOLOGY was first of all the methods which had been used in the scientific research of outer phenomena that led to a theo- retical psychology, the first outlines of which Plato, the founder of logic and ethics, formulated, at least for thought and volition. This same connection can also be seen in the important influence that the example of the methods of natural science has had upon the formation of modern psychology. Even before practical psychological methods were formed in analogy to the latter, the idea of strict and universal reg- ularity in mental phenomena was recognized. The great metaphysicians of the seventeenth century, Spinoza and Leibniz, were convinced that mental phenomena agreed with the phenomena of outer nature in regard to the strict regularity of their course. The association psychology must be given credit for having turned this belief to ac- count by formulating certain psychological concepts which were of great help for empirical psychology. Hobbes ex- plained the strict regularity of our thought processes by means of the continuance of material movements in the brain and thereby created in the mental sphere an analogy to the physical principle of inertia. A century later Newton introduced into physics the idea of attracting forces, and then we find in the psychology of Hume also a kind of at- traction of ideas. Inertia and attraction were able to ex- plain the mechanical principles of the outer world. Founded on analogies with these, the concept of association in the mental sphere seemed to be designed to do the same for mental phenomena. Last of all we have Herbart, who went furthest with these mechanical analogies. Filled with the conviction that the regularity of mental life was similar to that of the heavens, he provided his ideas with all the characteristics of elastic bodies, which, enclosed within a narrow space, exerted pressure upon each other. PSYCHOLOGICAL METHODS 215 In spite of all this, such analogies left a great deal of room free for the building up of psychology itself. But, in more recent developments of the science, this was in danger of being limited by a direct transference of the methods of natural science to psychology, and this transference led so far as to give rise to the demand that psychology must be methodically based upon physiology. 2. Physiology the Basis of Psychology The influences of the natural sciences upon the methods of psychology are certainly not the only ones under which the latter have come, for the differences in method have certainly not been less than the differences in the general trend of psychology. And yet these influences have been of the greatest importance for our science at the pres- ent day. The opportunity for a direct attack by the natural sciences was given when the question as to the relation between observation and introspection had been decided in the sense that the latter could never become a scientific method. Out of this arose the demand to seek the methodical basis of the science of the soul in another department of science, and the most natural department was, of course, brain phys- iology. Comte’s protest against introspection 1 lost much in force because of his questionable suggestion that psy- chology should be based upon phrenology as Gall had de- fined the latter. In contradistinction to this, Maudsley demanded that psychology be theoretically based upon physiology. In a criticism of J. S. Mill’s work on Hamilton he proposed with great determination to substitute a purely physiological method in place of the method of introspec- tion to which Mill had assented . 2 In his chief work, The 1 Cf. p. 154. 2 This criticism appeared in The Journal of Mental Science, 1866. 216 HISTORY OF PSYCHOLOGY Physiology and Pathology of the Soul, he contended that it was impossible to attain any results by the old method; such an undertaking, he says, is just as hopeless as trying to illuminate the universe with one tallow candle. Mauds- ley supported his contentions partly by means of the cur- rent arguments of materialism. Material conditions are at the bottom of all psychical life, and, naturally, physiology is best able to give an account of these. The organic metab- olism of the brain is always influencing consciousness; nothing is, therefore, more certain than that psychical phenomena are dependent upon physiological conditions. More important, however, are the peculiar but purely psychological reasons that Maudsley brings forward. Since conscious life is not a continuous activity, consciousness cannot give sufficient information about the static states of the soul. Only physiology can teach us about the inactive state of the soul, which is not accompanied by consciousness. But even of the activities of the soul themselves, the most important take place without consciousness. This last ar- gument involves itself at best in a contradiction, since the hypothesis of unconscious psychical processes presupposes a certain amount of purely psychological knowledge. A similar attempt was made in Germany on the part of Horwicz, which tried to avoid such contradictions. After more or less lengthy discussions as to method, 1 he admitted in his Psychologische Analysen auf physiologischer Grund- lage (1872 to 1878) the necessity for a kind of introspection, but only for the sake of a preliminary orientation of the total mass of psychic activities. But it is the physiology of the bodily organism which is the real foundation, for the organ- ization of the soul corresponds to the organization of the body. It is by the physiological method that the scientist arrives at a division of psychical phenomena; and so in the same 1 Zeitschr. f. Philos, u. philos. Krit., Bd. LX, 1872, p. 170. PSYCHOLOGICAL METHODS 217 way should he determine the number and the characteris- tics of the mental elements and the laws of their combina- tion. This important support that the physiological method was promising psychology has an analogy in the relation- ship between some other sciences, all of which can be traced back to the influence of Comte’s classification of the sciences, where each one served as handmaid to a superior science, and where all were arranged in an ascending series from the least important to the most important. In this scale, psy- chology is related to physiology as physics to mathematics or as geography to astronomy. Against all this it has been objected that even if physical and psychical phenomena were still more closely connected, the absolute hetero- geneity of the two kinds of phenomena would make every conclusion carried over from the one department to the other merely an analogy. And, in fact, the psychology of Horwicz is built upon the insecure foundation of analogies. The chief part is played by the concept of assimilation in the physiological and in the psychological sense; a further analogy exists between the opposition of sensory and motor nervous activities on the one hand and the general division of our total psychical life into theoretical and practical activities on the other. Upon this Horwicz builds a divi- sion of psychical phenomena which in the main agrees with that “really perfectly correct skeleton of mental life which was set up by Wolff.” That such conclusions drawn from analogies could become a proof of or, worse still, a substi- tute for a psychologically determined division merely goes to show to how great a degree Horwicz had lost sight of the aims of psychology in his great admiration for the successes in the field of physiology. In quite a different sense did the physiological method become an aid to psychology in the physiological psychology of Wundt. That this is in the first instance psychology 218 HISTORY OF PSYCHOLOGY and that it attempts to investigate the processes of con- sciousness in the combinations they form among them- selves — all this follows from Wundt’s definition of psychology which was quoted above . 1 Physiological psychology at- tempts to deduce the psychical from the physical phe- nomena of life just as little as, for example, microscopical anatomy might attempt to give an explanation of the ca- pacities of the microscope from the facts of anatomy. Physi- ology is drawn upon partly for supplementary purposes, as, for example, in questions as to the physical basis of mental life, but this latter is not bounded by these facts but leads right on to the other problems of psychology that border upon philosophy. But partly and chiefly do we mean by physiological psychology the incorporation of the exper- imental methods developed by physiology. Of these ex- perimental methods in the broadest sense the most important part has been played by the methods of psychical measure- ment, which from the very beginning centred around the problem of a psychical scale. 3. The Development of the Methods of Psychical Measurement Nowhere do we see more clearly than in the development of the methods of psychical measurement what an influence upon the development of a method its subordination* to some theoretical point of view may exert even though the latter may in later years have to be sacrificed. It is certain that there is not one of the methods of psychical measurement that did not exist in its broad outlines before the time of Fechner. Yet it was only through him that these methods became a recognized part of experimental psychology. Even the concept of the psychical measure is much older than 1 See p. 162. PSYCHOLOGICAL METHODS 219 the psychophysics of Fechner . 1 And yet it was Fechner who was the first to bring the experimental methods into relationship with the problem of a psychical measure and in this way lead to a theoretical discussion of these methods. Not the discovery of a new method of procedure but merely a change in the point of view led to the rise of the methods of psychical measurement. The common starting-point of all these methods lies in those methods which are used to determine the size of physical quantities. Everywhere where the inaccuracy of sense-impressions led to unavoidable mistakes in observa- tion, there arose the necessity of approximating to the objective values as nearly as possible by means of increas- ing the number of observations. The systematic applica- tion of these methods of eliminating error to the problem of the determination of psychical measurement was left for Fechner to take up in his psychophysics. The classifica- tion and the names that Fechner gave to these methods of measurement have been repeatedly modified according to the peculiarities of the methods that have appeared most characteristic. For example, Ebbinghaus divides the meth- ods into those of stimulus determination and those of judg- ment determination; G. E. Muller into the methods of con- stant changes and of limits; and Wundt, who kept longest to Fechner’s division, recently divided them into gradation and enumeration methods. In the development of the methods there has been a gradual differentiation between those two chief groups, which became clear according to the problems allotted to them by Fechner. Now, according to Fechner, all methods exist for the purpose of bringing into relation definite parts of the scale of sensation with definite parts of the stimulus scale, so as to be able to measure sensation by some unit. 1 See below, Chapter IX. 220 HISTORY OF PSYCHOLOGY In calling these methods of measurement “psychophysical,” Fechner hints at the fundamental duty of psychophysics. The just-noticeable difference was taken to represent the unit of sensation. The methods could either find these units directly or arrive at them by calculation. The methods of the first kind, which because of their more natural procedure are in general the older, can be called the gradation methods ( Abstufungsmethoden ). In contra- distinction to these the methods of the second class were grouped together under the name of the “error” methods, a name which is not at all happy in describing the difference between the two classes. For every method has to reckon with unavoidable errors of observation and becomes in its exact manipulation an error method. And, in fact, the old experiments which attempted to find directly the just-no- ticeable difference have been mostly worked over again in new ways under the influence of the discussions arising out of the theory of error. (a) The Older Forms of the Methods Ernst Heinrich Weber came upon his most important discoveries in the sphere of psychical measurement with the help of the simplest and most natural of methods. He tried to find directly the least stimulus difference that could just be noticed. Since it was by experiments of this kind that Weber proved the law that bears his name, the method of least differences held for a long time the first place. As so often happens with investigators, who see for the first time in broad outline a new field of science, Weber an- ticipated or pointed the way to almost all the methods of psychical measurement that were later developed. When in determining the sensitivity of the sense of touch he placed weights simultaneously on the finger and the forearm, PSYCHOLOGICAL METHODS 221 whereupon the weight on the forearm appeared lighter, he was working according to what became later known as the method of equivalents. 1 He also let the same weights, which were in the ratio 39 : 40, be lifted many times, and main- tained, on the ground of the frequency of the right judg- ments, that the majority of people would be able to dis- tinguish by means of muscle-sensations two such weights without a previous long period of practice; in this he an- ticipated the method of right and wrong cases. 2 The method used with such success by Weber was called by Fechner the method of just-noticeable differences and ranked first among the methods for measuring difference sensitivity. 3 In its use, for example, in investigating the fineness with which differences of weight can be distin- guished, the method consists in determining the extent of the difference in the weight that is necessary in order to be just-noticeably perceived. Fechner saw the chief advan- tage of this method in the fact that the just-noticeable difference could be immediately perceived as the same for the sensation. The extent of the just-noticeable difference certainly leaves some free play to the subjective judgment, even though one may, so to say, come to some agreement with oneself as to the feeling of a small and just-sufficiently sensed difference and be able to reproduce this with sufficient accuracy in different tests. Now, although Fechner calls this method the most important tool of psychophysics, yet it is clear that he felt that its results are really of a prelim- inary nature, and that a real decision can be reached only by those methods that are founded upon the principles of the theory of error. Alongside of the method of just-noticeable differences has often been placed the method of mean gradations. The 1 Tastsinn und Gemeingefuhl, p. 548. 2 Cf. p. 128. 3 Elemente der Psychophysik, I, 1860, pp. 71 ff. 222 HISTORY OF PSYCHOLOGY chief idea of this method is to determine equally large differ- ences of sensation by immediate judgment. In this way this method forms a natural continuation of the problem as for- mulated by Fechner for the methods of measurement. In- stead of taking the roundabout way of just-noticeable differ- ences, it appeared much more profitable to investigate the relations between the systems of stimulus and sensation by means of judging more than noticeable differences. Plateau 1 had been the first to use for psychical measurements in this sense the possibility of determining a sensation midway between a stronger and a weaker one with a fair degree of certainty. He asked eight persons who had had practice in painting to determine a gray midway between a pure white and a deep black, and he found the result to be almost identical with all of them. We cannot here go further into the numerous modifications of these methods, as, for ex- ample, the method of double stimuli introduced by Merkel 2 whereby a stimulus is to be found that gives twice as strong a sensation as a given stimulus. The theoretical importance of such a mean sensation is determined by one’s general opinions of psychical measurement. (b) The Influence of the Theory of Error After the method of just-noticeable differences Fechner ranks the method of right and wrong cases and the method of average error. The two latter attempt to determine the relation between the immediate results of observation and the values sought by psychical measurement on the basis of the theory of error. In the determination of ab- solute sensitivity the method of mean gradations goes over into the method of equivalents, where the observer has to 1 Bulletins de Vacademie royale de Belgique, t. XXXIII, 1872, p. 376.' 2 Phil. Stud., Bd. IV, 1888, p. 545. PSYCHOLOGICAL METHODS 223 choose a stimulus that appears the same as a given one, other things being equal ( e . g., on a different part of the skin). In using the method of average error the observer has to arrange two stimuli so that they shall be equal; the average error made in doing this is brought into relation with the difference-threshold. The method of right and wrong cases calls for numerous judgments upon one and the same stimulus lying near to the difference-threshold. Rather hypothetical discussions in the theory of error are required in order to come to any definite conclusions as to the nature of the difference-threshold from the relation | ^ j between the number of right cases (r) and the total number of cases (■ n ), which results from employing this method. In these methods also Fechner was not without prede- cessors. Especially in photometrical determinations had the importance of the average error been previously shown. Steinheil 1 had considered the average error, which was made in arranging two similarly bright fields in the prism pho- tometer, as a measure for the possibility of differentiation of two brightnesses. And the method of right and wrong cases had been used in experiments as to the possibility of deter- mining the differences of tone intensity, which had been carried out by Renz and Wolf under Vierordt’s direction . 2 The theoretical discussion, however, first arose because Fechner treated these methods according to the principles of the theory of error. In order to be able to draw definite conclusions from the size of the average error as regards the certainty of the observation, a knowledge of the distribu- tion of the errors or of the law of error is necessary. The first attempts to arrive at the true value of a quantity from 1 Elemente der Helligkeitsmessungen am Stemenhimmel, 1837. Cf. below, Chapter IX, 1 (6). 2 Vierordt’s Archiv, 1856, Heft 2, p. 185. 224 HISTORY OF PSYCHOLOGY quantities that contain errors of observation are met with in the eighteenth century. 1 Roger Cotes (1722), in an investi- gation of the errors of values obtained in observation, com- pared the errors to weights of reciprocal value, which are to be added on to the separate points; the centre of gravity of such a system coincides then with the true value. The im- portance of the arithmetical mean of a series of observations of the same objective quantity was first recognized by Thomas Simpson in 1757. He showed also how the relia- bility of such a mean value increased with the increase of the observations. Lambert, in 1760, reached more accurate conclusions in his photometrical investigations. If negative and positive errors appear equally often, and if, further, the supposition is valid that large errors occur less often than small ones, then the arithmetical mean is the truest value. In Lambert’s Theorie der Zuverldssigkeit der Beobachtungen und Versuche there are fairly arbitrary presuppositions as to the calculation of the mean. A test of the method of finding the mean by the more accurate help of the theory of probability is first found in Lagrange. 2 Daniel Bernoulli, in a publication of the Saint Petersburg Academy on the compensation of errors of obser- vation (1778), tried to supply the want of a special form for the law of the distribution of error. For the probability (; y ) of an error (A) Bernoulli established the equation: If we imagine the separate values A arranged along an abscissa, then the probability curve is a semicircle with the radius r and the centre A = 0. If a, b, c . . . are the ob- served values and x the most probable value, then the er- 1 Cf. the sketch of the history of the theory of error in G. F. Lipps, Die psychischen Massmethoden, 1906, pp. 33 ff. 2 Miscellania Taurinensia, Bd. V, 1770-1773. PSYCHOLOGICAL METHODS 225 rors of observation (A) are represented by the differences a — x, b — x, c — x. . . . The value x itself is deter- mined by the condition that the product -\J r 1 — (x — a) 2 . -\J r 2 —(x — b) 2 . -yj r 2 — (x — c) 2 be a maximum. With this Bernoulli had given a formal so- lution of the problem, but his law of error took for granted the same finite field of error for all series of observations. It was impossible by means of it to do justice to the dif- ferences in the certainty of observations, which are seen in various distributions of the errors as when they crowd around the middle value or are scattered over a larger area. A strictly valid theory of error was first obtained by Gauss. 1 Assuming that by repeated immediate observations of a quantity the arithmetical mean of all the observations is the most probable value, he deduced for the probability ( y ) of an error (A) the famous formula h A y— — -e-ft 2 A 2 . y' 7 r where the parameter h gives a measure for the accuracy of the observations. If, again, the observed values are denoted by a, b, c, . . . and the most probable value by x, then in this case the product h h h g-hKa-x ) 2 . g-ft!(6-z) 2 . g-hKc-x)* # , . V 7T 1 / 7T V 7T must be a maximum. And this is the case if the sum of (o— x) 2 + (b— x) 2 + (c— x) 2 . . . be a minimum. And with this Gauss arrived again at the method of least squares, which he had used since 1795, and 1 Theoria motus corporum ccdestium, 1809. 226 HISTORY OF PSYCHOLOGY in regard to which he could prove that it retained the best combination of observations with any law of error. 1 An analogous method of treating observations without the sub- stitution of a law of error had already been developed by Laplace in his Theorie analytique des Probabilites (1812). But it was Gauss who showed definitely that the mean error of a series of observations ought not to be defined as the mean of the simple errors but as the mean of the squares of the errors. And thus the problem of finding a measure for the reliability of a series of observations, which was first attacked by Lambert, was solved finally by Laplace and Gauss, not only in a special sense by the help of Gauss’s Law of Error, but also in a general sense by the use of the mean of the squared errors. Fechner took advantage of the help afforded by the theory of error and he worked upon the supposition that the pure errors, which remain after being separated from the constant errors, follow the ordinary laws of error. In that case the pure mean error could be set in reciprocal relation to the absolute value of the difference sensitivity. In the method of right and wrong cases he arrived at the relation between the relative number of right cases | ~ j and the distri- bution curve of the errors by the consideration that a right judgment would always occur if the error process would allow the difference ( 'D ) between the two stimuli to appear in its true sense. Judgments of equality Fechner divided equally between the right and wrong cases, so that he had only to deal with two categories of judgment. If, then, the error process follows the laws of Gauss, then hD h je- hlDl dD. V TT 0 1 Theoria combinationis observationum errorthus minimis obnoxice, 1821. PSYCHOLOGICAL METHODS 227 It follows further that out of -L we can calculate h, and this lb is a measure for the difference sensitivity. Since Fechner valued the usefulness of his methods in the main with respect to testing Weber’s Law, the knowledge of this value h was sufficient. If it remained constant as long as the stimulus difference D kept the same relation to the normal stimulus, then the constancy of the relative difference sensitivity was guaranteed and with that the validity of Weber’s Law. Be- sides this there resulted a purely mathematical relationship between the method of right and wrong cases and the mean error from the hypothesis that the measure of precision (, h ) is identical with the measure of precision resulting from 1 the mean error . 7"=~ . AmV-rr The most important changes in these methods resulted from the different ways in which the judgments of equality could be regarded. G. E. Muller, in his Grundlegung der Psychophysik (1879), introduced a new point of view in re- gard to method, inasmuch as he made a distinction between the fact of there being a difference-threshold and the occur- rence of chance errors of observation. The judgments of equality (z) are not equivalent to plus or minus judgments of difference. They seem rather to point to the fact of the threshold ( i ) being present, whereas the other judgments come within the scope of the error process. In this way he arrived at the following equations: ¥ D -* ) L = 1 , h _ Ce-wdD; n 2 Vi T 0 fcD + i) h (D-i) -h^dD- Je-h^dD) . o 228 HISTORY OF PSYCHOLOGY The relation between the values h and i would thus become an empirical question to which an answer could be given by means of experiments. The most recent developments of the methods of measure- ment have been in part influenced by the attempt to find an analytic presentation of the frequency of judgments which shall be free from the special presuppositions of Gauss’s Law of Error. Indeed, Fechner had tried to give due atten- tion to the asymmetry of a series of observations. In an asymmetrical distribution the arithmetical mean no longer coincides with the most probable value. The deviations must, therefore, be calculated from the “density value” or median. We have, then, an error curve on both sides of the median, and its course is the same as the error curve that is common to both sides in a symmetrical distribution. With such a two-sided or divided Gauss’s Law Fechner tried to represent asymmetrical types of distribution in his posthumous KolleJdivmasslehre (1897). 1 On the other hand, along with the distrust of the use- fulness of such mathematical aids, the inclination grew up to determine psychical values without making use of com- plicated formulae by means of a so-called immediate method. In the “method of many cases” there are not only the above- mentioned categories of judgment but also the cases of decided difference, of more-than- just-noticeable difference. It had been found necessary to give a different treatment to these different classes of judgments, and this led to the attempt to substitute for the analytic representation of the frequencies of judgment a frequency curve formed from the empirical distribution of the judgments and then to make the area enclosed by such a curve, called by G. E. Muller the ideal area, the basis for further calculation. This emancipation from one-sided mathematical presuppo- 1 Cf. G. F. Lipps, op. cit., pp. 89 ff. PSYCHOLOGICAL METHODS 229 sitions naturally led to an expansion of the field in which the methods of psychical measurement were used. And this was not only true for experiments according to the im- pression method, for which the methods of measurement were at first particularly adapted, but also for many exper- iments according to the expression method. (c) Connection with the Expression Methods These, the most recent methods of experimental psy- chology, were originally physiological or registration methods, the use of which for psychological purposes had arisen out of chance observations. We have already remarked briefly on the reaction method ; 1 but the other expression methods also arose out of physiological investigations. After the observations of C. Bell 2 on the bodily expressions of the separate affections, the work of Darwin 3 is the best known. He found such an intimate connection between the emo- tions and their forms of expression that the latter could scarcely exist if the body remained passive. But the real psychological importance of the organic changes for the rise of the emotions was first pointed out by William James. The same idea was worked out in greater detail by C. Lange , 4 who brought seven of the most important affections, e. the corresponding stimulus /3 relation and, further, let the relative threshold v have the same relation to

(f) can be deduced from the actual behavior of the value of the difference-threshold, *(»■) then there follows at once, by putting e * = 9 (r), the corrected formula of measurement: s = tc log $ (r), and out of this, by differentiation, the corrected fundamen- tal formula: ds = K ‘ ^ • dr (r) The function 4> (r) is, in accordance with the upper and lower deviations, convex toward the axis of the curve for PSYCHICAL MEASUREMENT 259 small values of r; and as r increases it approximates to a straight line and then becomes concave toward the axis. The turning-point lies at the maximum of the relative dif- ference sensitivity. For the interpretation of the validity of such a formula of measurement Muller admitted two alternatives. Either the sensation intensity s is proportional to the psycho- physical activity E, and this latter increases within certain limits almost like the logarithm of the stimulus r, or, con- versely, there exists approximate proportionality between the two last processes, so that the sensation intensity increases in arithmetical progression, while the psychophysical ac- tivity increases in geometrical progression. According to the first view, s = k"E, and for the nervous excitation E (psychophysical activity) we have the equation E = k' log $ (r), which Muller called the formula for the measurement of nervous excitation. According to the second view, and s = k .log E E — (r) are the expressions for Fechner’s psychophysical law. The first view leads to a physiological interpretation of Weber’s Law, and Muller emphatically supported such an interpretation as against the psychophysical one. First of all, a logarithmic relation between two physical states is easily thinkable. The difference, for example, in height above sea-level of two towns, where the barometer is B and b B respectively, is equal to C . log — , where C is a constant o 260 HISTORY OF PSYCHOLOGY dependent upon various circumstances. And the stimulus- threshold can easily be explained because of physiological inhibition. Muller also directed his criticisms against the psycho- logical interpretation of Weber’s Law. According to this in- terpretation two sensations, in order to appear to us dif- ferent in a constantly noticeable manner, must not show a constant difference to each other but rather must form a constant ratio. This leads to the equation: V (r) (r) dr, where p is a constant. The same equation can be deduced from s = ic . ( (r) ) p . In this manner he opposed the psycho- logical point of view held by Plateau, Brentano, and others. Hering’s standpoint is, according to Muller, just as un- tenable. In his experiments with weights he ought not to have taken as his question whether two weights of 1,000 and 2,000 grammes appear to differ by the same amount of weight as two weights of 100 and 200 grammes respectively. He ought to have raised the real psychological question as to whether the two former produce an equally noticeable difference in sensation as do the two latter. We do not perceive the differences or relations of given sensations but only the noticeability of these differences and relations, and we judge these latter as to equality or difference. What difference in weight or what relation of weights we conceive as the outer cause of a difference of two weight sensations noticeable to any degree depends entirely upon our ex- perience. And this makes invalid Hering’s objection that the absence of any proportion between sensation and size of weight would make impossible the acquisition by practice of mechanical skill; this learning rests upon associations formed between weight sensations and the ideas of the PSYCHICAL MEASUREMENT 261 amount of strength to be exerted. This substitution of the noticeability of sensations in place of the conception of their size stands the test of any further arguments of Hering. The latter might contend that if the size of a sensation corre- sponding to the length of a given line were to increase slower than the line, then two triangles geometrically similar but of different sizes would have to appear to us as dissimilar, since the relation of the three sides in each of the triangles would be quite different. To all of which Muller would reply that in such a case the differences in the lengths of the sides would appear equal precisely in accordance with Weber’s Law. Muller’s criticism was directed against all other concep- tions of psychophysics, in so far as he sought to show the untenability of the psychophysical view, as well as of all non- physiological theories. It was in the main this keen and radical attack that led Fechner to subject the principal prob- lems of psychophysics to a revision . 1 If the criticism of Muller was valid, then psychophysics was nothing but an historical relic; and so he once more set himself to meet all attacks with the picturesque and proud statement that a post by being shaken becomes looser and looser, but a tree, if it is not torn down, will only thereby root itself more firmly in the ground . 2 Fechner outlined clearly and sharply the physi- ological and the psychophysical points of view between which it seemed to him a decision must be made. Out of the well-known formulae there follows for the latter a stim- ulus-threshold, whereas for the former there is none. Ac- cording to the psychophysical point of view Weber’s Law is fundamental, but according to the physiological point of view it has no validity for inner psychophysics. If this latter is true there can be no physical principle by means of which the relation of the intensities of two physical 1 Revision der Hauptprobleme der Psychophysik, 1882. 2 Op. cit., Vorrede, p. 5. 262 HISTORY OF PSYCHOLOGY T processes - can be translated into a difference of the suc- r ceeding dependent processes E' — E in such a manner that / T to n times - would correspond n times the difference of E'—E. The physiological examples of Muller and others only show the dependence of end result (e. g., the height of the pull of a muscle) upon the exciting stimulus but not the real dependence between two processes in motion, with which psychophysics is alone concerned. The fact of the inner threshold cannot be explained by means of resistance in the conductivity of the central substance, because the inhibition follows according to the principle of relative weakening and so can never die out. Again, the non- contradictory mathematical correlation of a whole system of formulae supports the psychophysical view-point. And, lastly, the conception of the whole physical process of the universe as a psychophysical one necessarily presupposes a psychophysical interpretation of the formulae of measure- ment. We see again in all this how Fechner’s whole thinking, rooted as it is in profound but fantastic conceptions, can never be reconciled with the demands of purely empirical thought. In the meantime, however, there sprang up a third interpretation of Weber’s Law — the psychological in- terpretation. ( b ) The Psychological Interpretation of Weber’s Law The psychological interpretation of Weber’s Law ap- pears with constantly increasing clearness in the thought of Wundt. Even in 1863, in his Lectures on Human and Animal Psychology, he was striving toward a psychological conception of Weber’s Law. He pointed to the meaning of the act of comparison and saw in our relative judgment PSYCHICAL MEASUREMENT 263 a proof of the purely psychological nature of this law. 1 Weber’s Law cannot be deduced either from the physiological peculiarities of the nervous substance or from a functional relationship between the physical and the psychical, for it is founded in the psychical processes which are at work in the comparison of sensations. It is in this sense not a law of sensation but a law of apperception. Even though in the first edition of his Principles of Physiological Psychology (1874) the logarithmic equation set up by Weber’s Law was taken to represent the dependence of the sensation upon the physiological process, yet later this mathematical rela- tionship was conceived as one between purely psychical factors. In this way Fechner’s formula of measurement could be brought into a form in which it contained only homogeneous terms. So that now sensation and stimulus do not enter into any functional relationship, but the law only tells us how the degree of noticeability of a sensation changes with the intensity of the sensation. If we denote a constant degree of noticeability by k, and the change in the sensation intensity corresponding to it by A E, then 7 A E k = c "E is the empirical expression for the observed facts. The growth of the sensation E must, then, be assumed to be proportional to the stimulus. Following this interpreta- tion, we have in Wundt’s survey of the position his attempt to explain the physiological processes by means of a hypo- thetical apperception centre. His analysis of the inhibition processes which occur in this centre during the conduction of nervous processes is an example of a psychophysical analysis of complex cerebral functions which is intended to show that the psychological interpretation need by no 1 Op. cit., I, pp. 133 /. Cf. also above, p. 134. • 264 HISTORY OF PSYCHOLOGY means come into contradiction with our knowledge of phys- iological nervous conductivity. In just as decided a manner did Theodor Lipps , 1 who at first started with a psychophysical interpretation, advance toward a psychological interpretation, in which the growth of sensations is proportional to the growth of stimuli, and the facts of Weber’s Law are deduced from the universal and fundamental psychological law of the relative quantitative identity of the elements of a whole . 2 The total quantity appears reduced in proportion to its undividedness. For the manner of this reduction we can get the following for- mula: If component parts already present (m) are increased by new homogeneous parts, then the psychical quantity of the increase undergoes such a reduction that we can put n for the increase in quantity the formula — . C, where m + n C is a constant. This formula expresses immediately the law of relativity, according to which a whole, in regard to its power of making an impression, appears to be increased in an equal manner if it undergoes an increase that is rela- tively equally large . 3 In this manner the size of the im- pression is determined by a purely psychomechanical process. If, however, equal and absolute differences in stimuli are found with the help of the gradation method, on the ground of a judgment of supraliminal differences, then there must occur an apperceptive division of the whole, according to which the absolute increases play their part without any reduction. 1 Grundtatsachen des Seelenlebens, 1883, pp. 75 /. “ Die Quantitat in psychischen Gesamtvorgangen,” Sitzungsber. d. philos. -philol. u. d. hist. Kl. d. Kgl. Bayr. Akad. d. Wissensch., 1899, III, pp. 400 ff. 2 “Das Relativitatsgesetz der psychischen Quantitat und das We- bersche Gesetz,” op. tit., 1902, I, pp. 1 ff. Cf. also W. Wirth, Arch, f. d. ges. Psych., Bd. XIV, 1909, pp. 217 ff. 3 Psychologische Studien, 2 Aufl., 1905, p. 253. PSYCHICAL MEASUREMENT 265 In this way Lipps approaches Wundt very closely in his assumption of a difference in the manner of judging just- noticeable and more-than-just-noticeable differences. In spite of this, the difference remains that Lipps asserts the ratio between the stimuli and the unconscious psychical processes and not between the stimuli and the sensation in- tensities, i. e., simple contents of consciousness. In accor- dance with this, in explaining absolute judgment he has re- course again to the unconscious processes. A division into parts of a content of consciousness is altogether meaning- less, but we can conceive of such a division in regard to unconscious real processes. Among the other opinions that approximate to the psy- chological interpretation we find the one of G. Heymans , 1 in which Weber’s Law is subordinated to the more gen- eral phenomenon of psychical inhibition. He observed that qualitatively similar but locally different sensations tended to crowd each other out, and this expressed itself as an in- hibition in an increase of the stimulus or difference-threshold. Weak sensations are crowded out of consciousness by the stronger ones just in proportion to the intensities of the latter. An extension of this law to apply to the weak sen- sations of difference is all that is required to explain the general content of Weber’s Law. The difference-threshold is a case of inhibition and Weber’s Law is a special case, i. e., a limiting case of the law of inhibition. All this as- suredly calls to mind the Herbartian principles governing the mechanism of ideas. And yet what a difference be- tween the old and imaginary statics and mechanics of ideas and this new theory of inhibition! The former in- cluded the whole of consciousness but this only a compara- tively small group of psychical phenomena. In the former, brilliant mathematical speculation into the unlimited field 1 Ztschr. f. Psych, u. Phys., Bd. XXVI, 1901, pp. 305 ff. 266 HISTORY OF PSYCHOLOGY of the possible challenges our admiration; in the latter, we meet the more modest results which have been laboriously gleaned from the field of experience. These forms of the psychological interpretation seemed also, however, to be subject to the general objections which von Ivries had previously directed against Fechner’s psy- chophysics . 1 Meinong 2 renewed this argument in the fol- lowing form: In general, equal differences may cause un- equal sensation differences and equal sensation differences may point to unequal differences in stimulus. The dis- parity of two psychical contents corresponds neither with their absolute nor with their relative stimulus difference and can only be brought into a close relationship with the latter. The facts of Weber’s Law allow, therefore, of no other conclusion than this, that to each definite value of sensation difference there corresponds one and only one value of the relative stimulus difference, and, conversely, one and only one value of sensation difference corresponds to each value of the relative stimulus difference. In the deduction of the formula of measurement the formation of the difference of two sensations en—e is the point most open to attack. Sensations cannot be added or subtracted. And if the separate e is conceived of as a number of degrees of noticeability we do not thereby gain any information as to the content of these degrees. The close connection which Fechner thought to exist between the principle of psychical measurement and the psychophysical interpretation of Weber’s Law has been destroyed. In spite of all the polemics against Fechner, it was once thought that psychology would achieve its object if it determined the validity of Weber’s Law in every de- partment; but at the present time we have progressed far 1 Cf. pp. 225 f., above. 2 Ztschr. f. Psych, u. Phys., Bd. XI, 1883, pp. 81 ff., 230 ff., 353 ff. PSYCHICAL MEASUREMENT 267 beyond this one-sided view. The inner psychophysics of Fechner, which led to a perfectly transcendental metaphysic of consciousness, has long ago been relinquished. There has been retained, however, in experimental psychology, the con- cept of psychical measurement and with it the task of ar- ranging a relation based upon number between a mani- foldness of correlated psychical elements and a field of outer processes . 1 1 Cf, G, F. Lipps, Grundriss der Psychophysik, 1903, p. 40. PART III A HISTORY OF THE MOST IMPORTANT PSYCHOLOGICAL THEORIES CHAPTER X THEORIES OF SENSATION If psychology feels itself called upon to take the same fundamental position among the mental sciences as physics has taken among the natural sciences, it would seem perti- nent to raise the question as to whether there has not oc- curred in the history of psychological theory a reaction similar to the one which occurred in the history of physical theories due to the so-called mechanical conception of the universe. What a gulf separates modern natural science from the Aristotelian physics dominant during the Middle Ages! Not only do changed conceptions lie at the bottom of present-day theories, but the fundamental thought, the reduction of all phenomena to the movement processes of the smallest parts, has become a new standard for all physical theories. In psychology, however, we do not no- tice any such radical change of position in regard to the content of consciousness; there is at most a suggestion of this , 1 and even then in a different sense, so that we see in the history of psychological theories no such thoroughgoing reaction as we do in the case of the natural sciences. Nevertheless, we do note an analogous transformation 1 See pp. 43 and 209. 268 THEORIES OF SENSATION 269 in some departments, as, for example, in sense-perception. The more modern theories of sense-perception, which trace the rise of percepts out of elementary processes, excel early attempts at an explanation of perception as much as the mechanical theory of heat excels the earlier theory of a heat material. That modern psychology offers a more exact basis for attempts to establish a psychical mechanics, for- merly undertaken in a very questionable manner, can be seen in part in the determination of psychophysical con- stants. Each of the more modern physical theories includes certain kinds of physical constants. The physics of Aris- totle explained the fall of a body by the desire of the body to reach its natural place, the centre of the earth. The theory of Galileo about a falling body led, on the other hand, to the determination of a physical constant, i. e., gravity. It is possible that the determination of psychophysical con- stants, such as difference-thresholds, reaction-times, scopes of consciousness, etc., has an analogous meaning for psycho- logical theories. Do these constants, as in physics, result in hypotheses? Without doubt there are hypotheses in psychology, as, for example, those about the physiological processes that underlie psychical phenomena; in this sense we speak of hypotheses of light sensation or of the hypothetical phys- iological processes underlying the feelings. The analogy between these and the real hypotheses of natural science is, however, a loose one. The ultimate physical theories, like that of the discontinuity of matter, of its kinetic-elastic or kinetic-electrical composition, contain within themselves presuppositions as to the substratum into which the phe- nomena are to be transformed. We do not in psychology, to continue the same examples, transform visual sensations into retinal stimulations or feelings into changes in inner- vation. There have been, it is true, attempts in modern 270 HISTORY OF PSYCHOLOGY psychology to transform the content of consciousness in the same empirical manner as physics has done with its phenomena . 1 But in the history of psychology any such transformation, which must necessarily have led to real psychological hypotheses, always fell within the scope of metaphysics. Such hypotheses are excluded from pure psy- chology because a hypothetical content of consciousness, the existence of which is only presupposed and not proved, is a concept that contradicts the phenomenological point of view. Contents of consciousness can be considered hy- pothetical only in the sense that we do not perceive them as separated and isolated, but that we deduce them from their effects; an example of such is the part certain difference tones of a high order play in the consonance theory of F. Krueger . 2 Such a psychological hypothesis does not, like the physical, reach over into another sphere of reality, for the hypothetical content of consciousness is lacking only in the conditions necessary for its acceptance such as the other contents of consciousness possess. And with this is closely connected the fact that the oppositions in principle, which in natural science are first met with among the hypotheses, are in psychology to be observed in the separate theories themselves. By far the greater number of psychological theories are concerned with conscious experiences with which a so-called outer experience is connected. The processes of sensation and perception have from the very beginning challenged theoretical explanation. In the field of subjective conscious states the theories of feeling and will have been the most important. Within the theories of sensation we can further distinguish general theories and theories dealing with spe- cial sensations, e. g., vision and hearing. 1 See p. 209. 2 Psych. Stud., Bd. V, 1910, pp. 319 ff. Cf. below, 3 (d). THEORIES OF SENSATION 271 i. General Theories of Sensation The distinction between sensation and perception be- longs only to the most modern concepts of psychology, and accordingly in historical development theories of sensation correspond entirely with those of perception. And yet in the historical development we can recognize the material distinction between the processes of sensation and those of perception. The theories of sensation have always been dependent upon physiological knowledge; apart from iso- lated anticipations, any advance of the former has been dependent upon the growth of the latter. As soon as the theories of sensation became freed from metaphysical hy- potheses they became closely affiliated to physiology. The theoretical utilization of the purely psychological arrange- ment of sensations, e. g., in the modern theories of color sensations, belongs to the most modern development. In the theories of perception, on the other hand, we notice from the earliest times that they are strongly influenced by definite philosophical theories. Although such oppositions have only stood out the more clearly because of the clearer definition of terms in modern times, yet we can trace them back in their broad outlines to the earliest times. The gradual separation between theories of sensation and theories of perception was in part prepared for by the analogous opposition in the theory of primary and secon- dary qualities, which is essentially connected with the name of Locke, even though it possesses a much longer prelim- inary history . 1 As primary differences Aristotle recognized the chief oppositions in the qualities of touch sensation, e. g., warm and cold, dry and wet. In the philosophy of the Arabians these were contrasted as primary qualities (qua- 1 Cf. Baeumker, Arch. /. Gesch. d. Phil., XXI, 1908, p. 492. 272 HISTORY OF PSYCHOLOGY litates primes or primaries ) with the remaining derivative qualities of sensation, and this was also the case with Al- bertus Magnus in his division into prima sensibilia and secunda sensibilia. In the fourteenth century, as shown in Heinrich von Hessen, the expression qualitates secundce gradually came to be adopted. It was, however, the me- chanical theories of the universe that revived the origi- nal Aristotelian concept of common contents of perception, such as size, number, and movement. Galileo called these the first accidents in contradistinction to the purely sub- jective qualities of sensation; and Robert Boyle used the expression “secondary qualities” for the purely sensory qualities. And in this way the contrast was formed for which Locke used the scholastic terminology of primary and secondary qualities. Although since that time the dis- tinction between sensation and perception has never been lost, yet even up to the present time several perceptions, e. g., the spatial, have been classified as special kinds of sensations, a thing which has been due to the influence of certain theoretical points of view, as, for example, of na- tivistic theories. However much the psychology of the senses has proved itself to be dependent upon physical and physiological knowledge, yet a psychological interpretation and utilization of the discovery of the physiological con- ditions underlying sensation and perception has very often been slow in appearing. The accommodation of the eye as a purely physiological fact was discovered by Kepler; its importance for the comprehension of depth has only been appreciated in modern theories. In the same way the facts of color-mixture were known for a long time before attempts were made to explain color sensations by means of an analogous stimulation of color substances in the eye. Among the general theories of sensation there predom- inated in earlier times fantastic conceptions of the origin THEORIES OF SENSATION 273 of sensations. Modern physiology was the first to bring forward a principle which led to a general theory of sensa- tion, namely, the principle of the specific energy of the nerves. (a) The Older Theories Ancient ideas as to the origin of sensation were confined within the circle of thought dealing with metaphysical theories of the soul. At the beginning of his treatise on sensations, Theophrastus classifies sensation theories into two groups: in those of the first group the sensation is ex- plained by the working of similar upon similar (™ 6 / j.ouo ha T-qv o/j-oioTrjTa) ; in the second a working of opposite upon opposite is presupposed (t