CORNELL 
 
 UNIVERSITY 
 
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 FROM 
 
 The Pjiilosophical Eevievr 
 
Cornell University 
 Library 
 
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 http://www.archive.org/details/cu31 92402901 271 9 
 
Series of /IDo&ern iPbilosopbers 
 
 EiliUii by E. Ilerskey Snenlh, Ph.D. 
 
 THE 
 
 Philosophy of Hume 
 
 AS CONTAINED IN EXTRACTS FROM THE FIRST BOOK 
 
 AND THE FIRST AND SECOND SECTIONS OF THE 
 
 THIRD PART OF THE SECOND BOOK 
 
 TREATISE OF HUMAN NATURE 
 
 SELECTED, WITH AN INTRODUCTION, V.\ra\ »»^^^^^ 
 
 HERBERT AUSTIN AIKINS, Pi^.T ^ ^g^ 
 
 Professor 0/ Philosophy in Trinity College^ N. C, ^^^l*^ -^ 
 
 Honorary Fellow 0/ Clark University J,wMi^^ 
 
 NEW YORK 
 
 HENRY HOLT AND COMPANY 
 
 1893 
 
^5. 
 
 \ 
 
 A- pGci^ 
 
 fA--*^ 
 
 Copyright, 1893 
 
 BY 
 
 HENRY HOLT & CO. 
 
 ROBERT DRUMMOND, ELECTROTYPER AND PRINTER, NEW YOKK. 
 
PREFACE. 
 
 It is unfortunate that most students of philosophy, 
 both in Germany and in Great Britain and America, 
 should gain their knowledge of Hume's philosophy 
 from the Enquiry Concerning Human Understand- 
 ing ; for in this work Hume sacrificed the thorough- 
 going philosophical scepticism of the Treatise of 
 Human Nature in order to carry out a system of 
 religious scepticism which finds its culmination and 
 best expression in the sections on " Miracles " and a 
 " Particular Providence and a Future State." When 
 these sections are quietly omitted the Enquiry rep- 
 resents neither Hume's philosophy nor his theology ; 
 and yet the length and difficulty of the Treatise have 
 made it necessary for college and university instruc- 
 tors to put editions of the Enquiry thus mutilated into 
 the hands of their students. To remedy this diffi- 
 culty I have taken the following selections from the 
 first book of the Treatise, in the hope that the main 
 doctrines of this great work will be no less intelligible 
 when much confusing detail is omitted. 
 
 Selections from the sections of Book II. on Liberty 
 and Necessity have been incorporated with the ex- 
 tracts from Book I. because Hume's doctrine of the 
 will is merely a special application of his doctrine of 
 causation and cannot be understood apart from it. 
 
 H. A. A. 
 
CONTENTS. 
 
 PAGE 
 
 Bibliography i 
 
 Biographical Sketch 13 
 
 Sources of Hume's Sceptical Philosophy .... 21 
 
 Brief Exposition of Hume's Philosophy 25 
 
 The System in Outline 25 
 
 Causation 36 
 
 The Conception of Reality .42 
 
 The Belief in Reality 45 
 
 Confidence in Reason 46 
 
 Inference 47 
 
 The Treatise and the Enquiry , 49 
 
 Hume's Influence upon Subsequent Thought ... 55 
 
 THE PHILOSOPHY OF HUME. 
 
 59 
 
 Introduction 
 
 Part I. — Of Ideas 61 
 
 Part II. — Of the Ideas of Space and Time and 
 
 Existence . 78 
 
 Part HI. — Of Knowledge and Probability .... 86 
 
 Part IV.— Of the Sceptical Philosophy 143 
 
 Index , 175 
 
BIBLIOGRAPHY. 
 
 HUME'S WRITINGS. 
 
 THE EARLIER EDITIONS. 
 
 Authorities : Edition of 1854 ; Mr. Grose in edition of 1886 ; 
 Leslie Stephen, History of English Thought, vol. I. , chap vi.; 
 Uebervveg, § 119; Lowndes' Bibliographer's Manual; Brunet's 
 Manuel du Libraire. 
 
 Treatise of Human Nature. Vols. I. and II., 
 London, 1739; Vol. III., 1740. Two vols., 8vo., Lon- 
 don, 1817. German translation by Jacob, Halle, 
 1790-1. French translation of Book I. by Renouvier 
 and Pillon, Paris, 1878. 
 
 Essays, Moral and Political. One Volume, Edinb., 
 1741 ; Second Edition, corrected, 1742 ; A Second 
 Volume, 1742; (Lowndes identifies this with the Phil. 
 Essays.) Third Edition, corrected, with additions, 
 London and Edinb., 1748. 
 
 Philosophical Essays concerning Human Under statid- 
 ing. London, 1748; Second Edition, with additions 
 and corrections, London, 1751. (Dr. Campbell speaks 
 of an edition "printed at London, in duodecimo, 
 1750.") German translation by Sulzer, Hamburg and 
 Leipzig, 1775; by Tennemann, Jena, 1793; by Kirch- 
 mann, Berlin, 1869. (Fourth edition in i888.) 
 French translation by Merian (published with Re- 
 nouvier and Pillon's translation of Book I. of the 
 Treatise under the title " Psychologic de Hume," 
 with an introduction by F. Pillon), Paris, 1878, 8vo, 
 581 pages. 
 
2 BIBLIOGRAPHY. 
 
 Alt Enquiry concerning the Principles of Morals. 
 London, 1751. German translation by Masaryk, 
 Vienna, 1883. 
 
 Political Discourses. Edinb., 1752. (To this edition 
 there is sometimes added "A List of Scotticisms.") 
 Reprinted in the same year. Italian translation, 
 Venezia, 1774; French translation, Amsterd., 1754, 
 1761, Paris, 1847. 
 
 Essays and Treatises on several Subjects. London and 
 Edinb., 1753-4. Four vols., fourth volume contain- 
 ing the Political Discourses, with additions and cor- 
 rections. New editions in 1756 (Lowndes), 1758, 
 1760, 1764, 1768, 1770, 1777, 1784, and frequently 
 afterwards. German translation of ' Tlie Four Phi- 
 losophers,' Glogau, 1768. 
 
 History of England. Vol. I., 1754 ; Vol. II., 1756 ; 
 Vol. III., 1760 ; Vol. IV., 1762. 
 
 Four Dissertations The Natural History of Re- 
 ligion, Of the Passions, Of Tragedy, Of the Standard 
 of Taste, London, 1757. 
 
 Les o;uvres fhilosophique de Hume. Traduites en 
 Iran?, (par J. -Bern, de Merian et Robinet), Amst., 
 1759-64, 5 vol. in-i2, ou Londres (Paris), 1788, 7 
 vol. in-i2. [This is from Brunet. Lowndes says 
 1783, instead of 17S8.] 
 
 Expose succinct de la Contestion .... entre M. Hume et 
 M. Rousseau. London, 1766. English translation 
 soon afterwards. German translation, Leipzig, 1797. 
 
 Two Essays (on Suicide and the Inunortality of the 
 Soul, originally prepared for the volume of Disserta- 
 tions but suppressed). London, 1767, anonymously. 
 Essays on Suicide and the Immortality of the Soul, 
 ascribed to the late David Hume. London, 1783, 1789; 
 Basel, 1799 (in English). German translation, Han- 
 nover, 1781. 
 
 The Life of David Hume, Esq., Written bv Himself. 
 AVritten in 1776, and published by Adam' Smith in 
 1777 together with his own letter to Wm. Strahan ; 
 also in edition of Essays, 1777. French translation, 
 Leipzig, 1777; Latin translation, 1787. The Auto- 
 biography is found in most editions of the History 
 
BIBLIOGRAPHY. 3 
 
 and of the Philosophical Works. It can also be had 
 separately. 
 
 Dialogues concerning Natural Religion. London, 
 1779. (Published by his nephew ; written in 1751.) 
 German translation by Schreiter, Leipzig, 1781. 
 
 Philosophical Essays on Morals, Literature, and Poli- 
 tics; by David Hume. To which is added, the Answer 
 to his Objections to Christianity, by Dr. Campbell. 
 Also, an Account of Mr. Hume's Life, an Original 
 Essay, and a few notes; by Thomas Ewell, M.D., of 
 Virginia. In two volumes. First American edition. 
 Philadelphia : published for the editor by Edward 
 Earle, 1817. 8vo. 561 -|- 616 pp. Dedication to 
 President Monroe. 
 
 The Philosophical Works of David Hume. Four 
 volumes, octavo. Edinburgh and London, 1826. 
 " The philosophical writings of Mr. Hume are here 
 for the first time collected in a uniform edition." 
 Other editions, Edinburgh, 1836 ; Edinburgh and 
 Boston, 1854 ; London, 1856. 
 
 The editions of 1826 and 1854, now out of print, 
 contain Hume's portrait, his autobiography, his will, 
 his account of his controversy with Rousseau, and a 
 list of the editions. 
 
 The best edition of Hume's Philosophical Vi'orks 
 now in print is that in four octavo volumes edited by 
 T. H. Green and T. H. Grose, Longmans, 1874 and 
 1886. Two volumes, which can be had separately, 
 contain the ' Treatise of Human Nature,' the ' Dia- 
 logues concerning Natural Religion,' and two critical 
 ' Introductions ' to the ' Treatise ' by Professor Green, 
 which cover in all 370 pp., and which are generally 
 admitted to be by far the best criticisms of Hume in 
 English. The two volumes of ' Essays, Moral, Politi- 
 cal, and Literary,' contain all the rest of Hume's philo- 
 sophical works. The first of these volumes also con- 
 tains Hume's Autobiography as well as an elaborate 
 ' History of the Editions ' and a ' List of Editions ' by 
 Mr. Grose. A cheaper edition of the ' Treatise ' is that 
 published in one volume at the Clarendon Press in 
 
BIBLIOGRAPHY. 
 
 1888, with a carefully-prepared index of nearly seventy 
 pages by Mr. L. A. Selby Bigge. The edition of Hume's 
 ' Essays ' published by Ward, Lock & Co. is not com- 
 plete, but is cheap and good enough for most pur- 
 poses. In this edition the sections of the ' Enquiry ' 
 on ' Miracles ' and a ' Particular Providence and a 
 Future State ' are placed at the back of the volume. 
 
 ON THE LIFE AND PHILOSOPHY OF HUME. 
 
 The literature is very abundant. For English 
 readers the following are perhaps the best and most 
 accessible. 
 
 On his Life : — Hume's Autobiography, with Adam 
 Smith's letters to Strahan; John H. Burton's 'Life 
 and Correspondence of David Hume,' Edinb., 1846, 2 
 vols., 8vo, containing portrait and fac-similes. New 
 edition, 1850. 
 
 On his Life and Philosophy : — Prof. Knight's 
 ' Hume,' Edinb. and Phila., 1886, sm. 8vo, x -f 239 pp., 
 portrait ; Prof. Huxley's ' Hume,' Lon., 1879, 1887 ; 
 N. Y., 1879, i2mo, vi + 206 pp.; French translation, 
 1880. 
 
 On his Philosophy : — Prof. Green's Introduction to 
 his edition of the ' Treatise ' ; Leslie Stephen's ' His- 
 tory of English Thought in the Eighteenth Century,' 
 Lon. and N. Y., 1876, vol. i., chaps, i. and vi. 
 Cardinal Newman's ' Grammar of Assent,' N. Y., 1870, 
 479 pp., is an excellent work to read in connection 
 with Hume's doctrine of belief, since from almost ex- 
 actly the same premises it arrives at diametrically op- 
 posite conclusions. 
 
 It is impossible to give a complete list of what has 
 been written about Hume ; for all the histories of 
 philosophy, the philosophical journals, and the great 
 writers, from Reid, Kant, and Jacobi to Lotze and 
 Spencer, have something to say about him. The fol- 
 lowing bibliography, however, may be useful. 
 
 'The History of the Works of the Learned' for 
 
BIBLIOGRAPHY. J 
 
 Nov. 1739 contains a review of the Treatise which 
 greatly annoyed Hume. 
 
 Adams, Wm. An Essay on Mr. Hume's Essay on 
 Miracles. London, 1752. 8vo, 134 pages. Second edi- 
 tion, London, 1754, 8vo. 
 
 Leland, John. A View of the Principal Deistical 
 Writers of the Last and Present Century. Lon., 1755. 
 8vo, 2 vols. Vol. IL, pp. 1-135: Mr. Hume. 
 
 Ca7npben, George. A Dissertation on Miracles. 
 With a Correspondence by Hume, Campbell, and 
 Blair. Edinb., 1797. 2 vols., Svo. Same, 1823, viii 
 + 560 pp. Campbell's Dissertation is also found in 
 the first Am. Ed. of Hume's Essays, 181 7. This crit- 
 icism of Hume was first published in 1761. Hume 
 considered its author the ablest as well as the most 
 courteous of all his critics. 
 
 Reid, Thos. 'Inquiry,' 1764 (Index in Sneath's 
 edition, 1892); Essays on the Intellectual Powers of 
 Man, 1785. 
 
 'The London Review' for 1776 contains an article 
 on Hume written immediately after his death and fre- 
 quently referred to. 
 
 [Home, Bishop George.] A Letter to A. Smith on 
 the Life, Death, and Philosophy of his friend D. Hume. 
 By one of the people called Christians. London, 1777, 
 1799. The same in his works, 1818, 8vo, Vol. IV., 
 pages 331-348. 
 
 [FraU, S. /.] An Apology for the Life and Writ- 
 ings of David Hume. With a Parallel between him 
 and the late Lord Chesterfield : to which is added an 
 Address to One of the People called Christians. By 
 way of Reply to his Letter to A. Smith. London, 
 1777. i6rao. XV + 167 pp. 
 
 jta/ii, Im. Kritik der reinen Vernunft, 1781, 1787; 
 Prolegomena, 1783, — especially pp. 3-10, 20-23, '23 of 
 the Mahaffy translation, Lon., i88g. 
 
 The Beauties of Hume and Bolingbroke. Second 
 edition. London, Kearsly, 1782. i2mo, xxxii -|- 
 262 pp. 
 
 Jacobi, F. H. David Hume ueber den Glauben, 
 Oder Idealismus und Realismus. Breslau, 1787. 
 
6 BIBLIOGRAPHY. 
 
 Boswell, James. Life of Johnson, 1791- N. Y. 
 ed., 1884, 4 vols. I. 355, 369, 375, 406, 439; II. 183; 
 III. 192, 335. 
 
 Merian, J. B. Sur le phenomenalisme de Hume. 
 21 pp. Berlin. Academic royale des sciences. Nou- 
 veaux Memoires. 1792-93. p. 417. 
 
 Walpole, Horace. Works. Lon.,1798. 4to. Vol. 
 IV., pp. 247-269: an account of the controversy be- 
 tween Hume and Rousseau, and correspondence be- 
 tween Hume and Walpole regarding it. See also 
 ' Walpoliana,' Lon., 1799. Two small volumes. 
 
 Smellie, Win. Literary and Characteristical Lives. 
 Edinb., 1800. Pages 149-209. Contains some ex- 
 tremely interesting personal reminiscences. 
 
 Kii-win, R. Remarks on some sceptical positions 
 in Hume's Enquiry concerning the Human Under- 
 standing. Royal Irish Acad. Trans. Vol. VIII., 
 1802, pp. 157-203. 
 
 Memoir of the Life and Writings of the Hon. Henry 
 Home of Kames. 1807. 2 vols., 4to. Contains "a 
 very long account of the publication and reception 
 of Hume's Treatise of Human Nature." 
 
 Ritchie, Thomas Ed^vard. Account of the Life and 
 Writings of David Hume, Esq. London, 1807. 8vo, 
 vii + 52opp. Contains also eight of Hume's 'Es- 
 says not inserted in his miscellaneous works,' and the 
 Expos^ sticcinct. 
 
 Easier, John. Critical Essays. Bohn's Library, 
 1856, pages 95-110. A review of Ritchie's biography 
 of Hume. Reprinted from 'The Eclectic Review,' Jan. 
 1808. 
 
 Vince, Samuel. The Credibility of the Scripture 
 Miracles vindicated in Answer to Mr. Hume. Cam- 
 bridge, 1809. 8vo, 78 pp. 
 
 Hardy, Erancis. Life of the Earl of Charlemont. 
 Lon., 1810, 4to. Most of the stories about Hume are 
 taken from this book. Several pages are quoted in the 
 preface to the first Am. edition of Hume's ' Essays.' 
 
 Blackwood's Magazine, Vol. III., 1818, pp. 653- 
 657: David Hume charged by Mr. Coleridge with 
 plagiarism from St. Thomas Aquinas, 
 
BIBLIOGRAPHY. 7 
 
 Private Correspondence of David Hume with sev- 
 eral Distinguished Persons between the years 1761 and 
 1776, now first published from the originals. London, 
 1820. 4to. xix + 285 pp. 
 
 Stewart, Dugald. Dissertation on the Progress of 
 Philosophy. Part 11. 1821. In Vol. VI. of his Works, 
 1829. Also in Encyc. Brit., 8th ed.. Vol. I., pp. 206- 
 2i8. See also pp. 268-274 for account of Hume's 
 Ethics by Mackintosh. 
 
 Mason, J. M. Writings. 1832. Vol. III. Contrast 
 between the death of Hume and Finley. 
 
 De Quincey, Thos. On Hume's Argument against 
 Miracles. 'Blackwood' for July, 1839, pp. 91-99. 
 Reprinted with other writings, Boston, 1854 and 
 1858 ; Edinb., 1890. 
 
 Erdmann, J. E. Versuch einer wiss. Gesch. der 
 neuern Philosophic. Leipzig, 1840. Vol. II., Part I., 
 pp. 162-192: Leben und Philosophie des Hume. 
 
 Lechler, G. V. Geschichte des englischen Deis- 
 mus. Stuttgart und Tiibingen, 1841. 8vo. Pages 
 425-436: Die Skepsis Hume's. 
 
 Murray, Thos. (Editor). Letters of David Hume 
 and extracts from letters referring to him. Edinb., 1841. 
 8vo, 80 pp. Also Lon., 1842. 
 
 New Englander, Vol. I., 1843, pp. 169-183: Hume, 
 Voltaire, and Rousseau. " A concise, impartial, and 
 authentic account of their lives and their assaults 
 upon Christianity." 
 
 Schlosser, F. C. Geschichte des i8ten und i9ten 
 Jahrhunderts. Heidelberg, 1843-49. 7 vols., 8vo. 
 English translation, Lon., 1843-44. Vols. I., II. 
 
 Quarterly Rev., Vol. LXXIIL, 1844, pp. 536-593: 
 Hume and his influence upon history. Contains 
 some interesting stories of Hume. 
 
 Brougham, Lord Heni-y. Lives of Men of Letters 
 and Science. 1845. 8vo. Chapter on Hume, pages 126- 
 166. The same in his ' Lives of Men of Letters of the 
 Time of George III.' London and Glasgow, 1885, 8vo, 
 pages 168-230. Largely biographical and sometimes 
 interesting. 
 
 North Brit. Rev., Vol. VII., 1847, pp. 539-560 : 
 
a BIBLIOGRAPHY. 
 
 Life and correspondence of Hume, A review of 
 Burton's book. 
 
 Burton, J. H. (Editor). Letters of Eminent Per- 
 sons addressed to David Hume. Edinb. and Lon., 
 1849. 8vo, xxxi + 334 pp. " These letters, though 
 interesting in themselves, are not illustrative of the 
 life and character of Hume." 
 
 Rogers, Henry. David Hume. Encyc. Brit., 8th 
 edition, 1852. Reprinted in 'New Biographies of Il- 
 lustrious Men,' Boston, 1857, pages 379-408. Very 
 largely biographical. 
 
 Walker, J. Hume's Philosophical Writings. Chris- 
 tian Examiner, Nov., 1854, pp. 421-439. An excel- 
 lent article. 
 
 Edgar, John G. Footprints of Famous Men. N. Y., 
 1854. Small 8vo. Pages 180-199: David Hume. 
 Gives some account of Hume's ancestry. 
 
 Villemain, A. F. Qiuvres. Nouv. ed., Paris, 
 1854-5. 10 vols., 8vo. Vol. VL 
 
 Cticheval-Clarigny, Narcisse. David Hume, sa vie 
 et ses ecrits, d'apres sa correspondance publie a Edim- 
 bourg. Revue des Deux Mondes, i nov. 1856, Vol. 
 VL, pp. 107-141. 
 
 Fischer, Kuno. Bacon und Nachfolger. Eng. 
 trans., Lon., 1857. Pages 468-496. 
 
 Feuerlein. Hume's Leben und Wirken. Der Ge- 
 danke. Vols. IV. and V. Berlin, 1863-64. 
 
 Masson, David. Recent British Philosophy. Lon. 
 and Camb., 1865. Small 8vo. viii + 414 pp. Gives 
 some account of Hume's influence, but does not say 
 much about it. 
 
 Papitlon, F. David Hume, precurseur d'Auguste 
 Comte. Versai.les, 1868. 
 
 Oliphant, Mrs. M. O. Historical Sketches of the 
 Reign of George II. Edinb., 1869. Chapter on 
 Hume reprinted from 'Blackwood,' Vol. CV., 1869. 
 Also in 'Littell's Living Age,' Boston, 1869, 8vo, pp. 
 202-221. Interesting. 
 
 Baumann, J. J. Die Lehren von Raum, Zeit und 
 Mathematik in der neueren Philosophic. Berlin, 1869. 
 2 vols., 8vo. Vol. II., pages 481-671. 
 
BIBLIOGRAPHY. 9 
 
 Hunt, John. David Hume. Contemp. Rev., Vol. 
 XL, 1869, pp. 79-100. Contains some stories of 
 Hume and historical matter concerning Hume's re- 
 ligious writings. 
 
 Schultze, W. F. Hume und Kant iiber den Causal- 
 begriff. Rostock, 1870. Svo, 39 pp. 
 
 Jodl, Friedrich. Leben und Philosophic David 
 Hume's. Halle, 1872. Svo, 202 pp. Only 17 pages 
 devoted to his life. 
 
 Southern Review, Vol. XL, 1872, pp. 92-120, 309- 
 336: Hume's Philosophy. "The analogy between 
 Hume and Kant is as marked in their deviation from 
 their own principles as in the resemblance of the 
 principles themselves.'' " The reign of Hume will at 
 length be ended, and we may hope that the sover- 
 eignty of Providence will be acknowledged in its 
 stead." 
 
 Compayre, Gabriel. La philosophic de David Hume. 
 Paris, 1873. 8vo, 514 pp. 
 
 Thornton, W. T. Old-fashioned Ethics and Com- 
 mon-sense Metaphysics. London, 1873. 8vo, vii -\- 
 298 pp. Pages 113-157 : David Hume as a metaphy- 
 sician. 
 
 Pfleiderer, Edmund. Empirismus und Skepsis in 
 David Hume's Philosophic als abschliesscndcr Zer- 
 setzung der cnglischen Erkenntnisslehre, Moral und 
 Religionswissenschaft. Berlin, 1874. 8vo, 540 pp. 
 "Containing good matter, but too much spun out." 
 
 Sinclair, John. Sketches of Old Times and Distant 
 Places. London, 1875. Svo, viii -|- 296 pp. Pages 
 165-196. 
 
 Spicker, Gideon. Kant, Hume, und Berkeley. Eine 
 Kritik der Erkenntnisstheorie. Berlin, 1875. ^^o- 
 
 Wirth, J. U. Pfleiderer: Empirismus und Skepsis 
 in D. Hume's Philosophic. 8 pp. Zeits. f. Philos., 
 Vol. LXVL, 1875, P- i°2- 
 
 Watson, J. Kant's reply to Hume. Jour. Spec. 
 Phil., Vol. X., 1876, pp. 1 13-134. 
 
 Riehl, A. Der philosophische Kriticismus. Vol. 
 I., Leipzig, 1876. Svo. Pages 63-161: Hume's skep- 
 tischer Kriticismus. 
 
10 BIBLIOGRAPHY. 
 
 Meiiioiiz, Alexius. Hume-Studien. I. Zur Ge- 
 schichte und Kritik des modernen Nominahsmus. 
 Wien, 1877. 8vo, 78 pp. From " Sitzungsber. d. k. 
 Akad. d. Wiss." " A very careful study of Hume's 
 nominalism." 
 
 Gizycki, G. v. Die Ethik David Hume's in ihrer 
 geschichtlichen Stellung. Breslau, 1878. Svo, xvii 
 + 357 PP- " ll^s most thorough exposition of Hume's 
 utilitarianism." 
 
 Ritter, Christian. Kant und Hume. Halle, 1878. 
 8vo, ss pp. 
 
 Thompson, J. P. Final Cause : a Critique of the 
 Failure of Paley and the Fallacy of Hume. With an 
 appendix on Huxley's Hume. London, 1879. ^^o, 
 ii + 22 pages. Also in his ' American Comments on 
 European Questions,' Boston, 1884, pp. 300-330. 
 
 Compayre, G. Du pretendu scepticisme de Hume. 
 Revue Philos., Tome VHI., 1879, pp. 449-468. 
 
 Morris, George S. British Thought and Thinkers. 
 Chicago, 1880. 8vo. Pages 234-264. 
 
 Pfleiderer, E. Meinong's Hume-Studien. Zeits. 
 f. Philos., Vol. LXXVII, 1880, pp. 248-263. 
 
 Quarterly Rev., Vol. CIL , 1880, pp. 287-330. 
 
 Runze, Max. Kant's Kritik an Hume's Skepti- 
 cismus: Greifswalder Inaugural-Dissertation, 1880. 
 
 The Hundred Greatest Men. London, 1880. Folio. 
 Contains portrait and brief biographical sketch. 
 
 Koenig, EJtnund. Ueber den Substanzbegriff bei 
 Locke und Hume. Leipzig, 1881. Svo, 75 pp. 
 
 Adamson, Robert. Hume. Encyc. Brit., 9th ed., 
 1881, pp. 346-355. 
 
 Espinas, A. La philosophic en Ecosse au XVHP 
 siecle et les origines de la philosophie anglaise con- 
 temporaine. Revue Phil., Tome XL, 1881, pp. 113- 
 132; XIL, 119-150. 
 
 Correspondance litteraire, philosophique et critique 
 par Grimm, Diderot, Raynal, Meister, etc. Paris, 1882. 
 16 vols., 8vo. Index in Vol. XA^I. 
 
 Sayous, Edouard. Les Deistes anglais et le Chris- 
 tianisme. Paris, 1882. 8vo., 211 pp. Chap. VIIL: 
 La decadence du deisme. ' The death-warrant of the 
 
BIBLIOGRAPHY. II 
 
 rationalistic school was signed by Hume as well as by 
 Wesley.' 
 
 Howison, Geo. H. Hume and Kant. Outline of 
 four lectures delivered at Concord School of Philoso- 
 phy, July, 1883. [Concord, 1883.] i6mo, 7 pp. 
 Same in German, San Francisco, 1884, 8vo, 7 pp. 
 
 McCosk, James. Agnosticism of Hume and Hux- 
 ley, with a notice of the Scottisli School. New York, 
 
 1884. 8vo, 10 + 70 pp. (Philosophical Series, VI.) 
 Stirling, J. H. Kant has not answered Hume. 
 
 Mind, Vol. IX., 1884, pp. 531-547; Vol. X., pp. 45- 
 72. See also The Secret of Hegel, Lon., 1865, In- 
 troduction: "Hume is our Politics, Hume is our 
 Trade, Hume is our Philosophy, Hume is our Re- 
 ligion." 
 
 Gordy, John P. Hume as Sceptic. Leipzig, 1885. 
 8vo, 69 pp. 
 
 Webb, T. E. Veil of Isis. Dublin and London, 
 
 1885. 8vo, xiii + 365 pp. Pages 67-124: Problem- 
 atical Idealism or Hume. 
 
 Seth, Andrew. Scottish Philosophy : a comparison 
 of the Scottish and German answers to Hume. 
 Edinb., 1885. 8vo, xii + 218 pp. 
 
 Stuckenberg, J. H. W. Grundprobleme in Hume. 
 Vortrag [gehalten in der philosophischen Gesellschaft 
 zu Berlin am 28 Februar, 1885] nebst der dabei statt- 
 gehabten Diskussion. Halle a S., 1887. 8vo., 35 pp. 
 
 Tarantino, G. (Docent in the University of Naples). 
 Saggio sul criticismo e suU' associazionismo di Davide 
 Hume. Napoli, 1887. 8vo, 75 pp. 
 
 Carrau, Ludovic. Philosophic religieuse en An- 
 gleterre depuis Locke jusqu'a nos jours. Paris, 1888. 
 8vo, 295 pp. Pages 92-157. 
 
 G. B. Hill (Editor). Letters of David Hume to 
 William Strahan, now first edited. Oxford, 1888. 
 8vo, xlvi -|- 386 pp. Fac-simile. 
 
 Case, Thomas. Physical Realism. London, 1888. 
 8vo, 387 pp. Pages 256-318. 
 
 Koenig, Edmund. Die Entwickelung des Causalpro- 
 blems von Cartesius bis Kant. Leipzig, 1888. Pages 
 205-246. 
 
12 BIBLIOGRAPHY. 
 
 Fraser, Alex. Visualization as a Chief Source of the 
 Psychology of Hobbes, Locke, Berkeley, and Hume. 
 Am. Jour. Psych., Vol. IV., 1891-92, pp. 230-247.^ 
 
 Stephen, Sir James Fitzjames. Horae Sabbaticse : 
 reprint of articles contributed to the Saturday Review. 
 Second Series. London and New York, 1892. Sm. 
 8vo. Pages 367-385. 
 
 Hyslop, James H. Hume's Treatise of Morals and 
 Selections from the Treatise of the Passions. Con- 
 tains an introduction of 66 pages and a bibliography. 
 Boston, 1893. i2mo, 275 pp. 
 
BIOGRAPHICAL SKETCH. 
 
 In his Autobiography, dated April i8, 1776, Hume 
 says : 
 
 "I was born the twenty-sixth of April 1711, old 
 style, at Edinburgh. I was of a good family, both by 
 father and mother. My family, however, was not 
 rich ; and being myself a younger brother, my patri- 
 mony, according to the mode of my country, was of 
 course very slender. My father, who passed for a man 
 of parts, died when I was an infant. I passed through 
 the ordinary course of education with success, and was 
 seized very early with a passion for literature, which 
 had been the ruling passion of my life, and the great 
 source of my enjoyments. My studious disposition, 
 my sobriety, and my industry, gave my family a notion 
 that the law was a proper profession for me ; but I 
 found an unsurmountable aversion to everything but 
 the pursuits of philosophy and general learning. 
 
 " In 1734 I went to Bristol, with some recommenda- 
 tions to eminent merchants ; but in a few months 
 found that scene totally unsuitable to me. I went 
 over to France with a view of prosecuting my studies 
 in a country retreat. During my retreat in France, 
 first at Rheims, but chiefly at La Fleche, in Anjou, I 
 composed my ' Treatise of Human Nature.' In the 
 end of 1738 I published my treatise. Never literfiry 
 
 13 
 
14 BIOGRAPHICAL SKETCH. 
 
 attempt was more unfortunate than my Treatise of 
 Human Nature. It fell dead-born from the press, 
 without reaching such distinction as even to excite a 
 murmur among the zealots. But, being naturally of a 
 cheerful and sanguine temper, I very soon recovered 
 the blow, and prosecuted with great ardor my studies 
 in the country. In 1742 I printed at Edinburgh the 
 first part of my Essays ; the work was favorably re- 
 ceived, and soon made me entirely forget my former 
 disappointment." 
 
 After an extremely unpleasant year spent as tutor 
 and guardian of the weak-minded young Marquis of 
 Annandale, Hume accepted in 1746 the invitation of 
 General St. Clair to act as secretary to the expedition 
 which afterwards attacked the French coast, and the 
 following year he attended him in the same station in 
 his military embassy to the courts of Vienna and 
 Turin. "These two years were almost the only in- 
 terruptions which my studies have received during 
 the course of my life." 
 
 " I had always entertained a notion that my want of 
 success in publishing the Treatise of Human Nature 
 had proceeded more from the manner than the matter, 
 and that I had been guilty of a very usual indiscretion, 
 in going to the press too early. I therefore cast the 
 first part of that work anew in the ' Enquiry concern- 
 ing Human Understanding,' which was published 
 while I was at Turin. But this piece was at first little 
 more successful than the Treatise of Human Nature. 
 
 " Such is the force of natural temper, that these dis- 
 appointments made little or no impression on me. I 
 went down in 1749, and lived two years with my 
 
BIOGRAPinCAL SKETCH. 15 
 
 brother at his country house, for my mother was now 
 dead. I there composed the second part of my essay, 
 which I called ' Political Discourses,' and also my 
 ' Enquiry concerning the Principles of Morals,' which 
 is another part of my treatise that I cast anew. 
 
 " In 1751 I removed from the country to the town. 
 In 1752 the Faculty of Advocates chose me their 
 librarian ; an ofifice from which I received little or no 
 emolument, but which gave me the command of a 
 large library. I then formed the plan of writing the 
 ' History of England.' I was, I own, sanguine in my 
 expectations of the success of this work. I thought 
 that I was the only historian that had at once neglected 
 present power, interest, and authority, and the cry of 
 popular prejudices ; and, as the subject was suited to 
 every capacity, I expected proportional applause. 
 But miserable was my disappointment : I was assailed 
 by one cry of reproach, disapprobation, and even de- 
 testation : English, Scotch, and Irish, whig and tory, 
 churchman and sectary, freethinker and religionist, 
 patriot and courtier, united in their rage against the man 
 who had presumed to shed a generous tear for the fate 
 of Charles I. and the Earl of Strafford ; and, after the 
 first ebullitions of their fury were over, what was still 
 more mortifying, the book seemed to sink into ob- 
 livion." 
 
 Yet some time later " the copy-money given me by 
 the booksellers much exceeded anything formerly 
 known in England," 
 
 In 1763 Hume accepted the Earl of Hertford's in- 
 vitation to join the British embassy at Paris, and was 
 shortly afterwards appointed secretary to the embassy. 
 
l6 BIOGRAPHICAL SKETCH. 
 
 He was much pleased with his reception in the French 
 capital ; but left in 1766 for Edinburgh, with the pur- 
 pose " of burying himself in a philosophical retreat." 
 After two years in London as under-secretary to 
 General Conway, Hume returned to Edinburgh in 1769 
 " very opulent (for I possessed a revenue of one thou- 
 sand pounds a year), healthy, and, though somewhat 
 stricken in years, with the prospect of enjoying long 
 my ease, and of seeing the increase of my reputation. 
 
 "In spring 1775 I was struck with a disorder in my 
 bowels, which at first gave me no alarm, but has since, 
 as I apprehend it, become mortal and incurable. I 
 now reckon upon a speedy dissolution. 
 
 " To conclude historically with my own character. 
 I am, or rather was (for that is the style I must now 
 use in speaking of myself, which emboldens me the 
 more to speak my sentiments) ; I was, I say, a man of 
 mild disposition, of command of temper, of an open, 
 social, and cheerful humor, capable of attachment, 
 but little susceptible of enmity, and of great modera- 
 tion in all my passions. Even my love of literary fame, 
 my ruling passion, never soured my temper, notwith- 
 standing my frequent disappointments. My company 
 was not unacceptable to the young and careless, as 
 well as to the studious and literary ; and, as I took a 
 particular pleasure in the company of modest women, 
 I had no reason to be displeased with the reception I 
 met with from them. In a word, though most men, 
 anywise eminent, have found reason to complain of 
 calumny, I never was touched, or even attacked, by her 
 baleful tooth ; and, though I wantonly exposed my- 
 self to the rage of both civil and religious factions, 
 
BIOGRAPHICAL SKETCH. 17 
 
 they seemed to be disarmed in my behalf of their 
 wonted fury. My friends never had occasion to vindi- 
 cate any one circumstance of my character and con- 
 duct ; not but that the zealots, we may well suppose, 
 would have been glad to invent and propagate any 
 story to my disadvantage, but they could never find 
 any which they thought would wear the face of proba- 
 bility. I cannot say there is no vanity in making this 
 funeral oration of myself ; but I hope it is not a mis- 
 placed one ; and this is a matter of fact v^fhich is easily 
 cleared and ascertained." 
 
 Hume's conviction that he had not long to live 
 turned out to be correct ; for on Sunday, Aug. 25, 
 1776, "he died in such a happy composure of mind 
 that nothing could exceed it." On Nov. 9 of the 
 same year Adam Smith wrote to Wm. Strahan " some 
 account of the behavior of our late excellent friend, 
 Mr. Hume, during his last illness," and in concluding 
 he said : " Upon the whole, I have always considered 
 him, both in his lifetime and since his death, as ap- 
 proaching as nearly to the idea of a perfectly wise and 
 virtuous man as perhaps the nature of human frailty 
 will permit." 
 
 That a professed sceptic should be described as 
 wise and virtuous, and that he could die peacefully 
 and cheerfully, seemed to most Christians of Hume's 
 time scandalous and incredible. No sooner, there- 
 fore, had Dr. Smith's account of Hume's happy end 
 been published in 1777 than it became the subject of 
 horrified comment and violent controversy. Boswell 
 ' mentioned to Dr. Johnson that David Hume's per- 
 sisting in his infidelity when he was dying shocked 
 
l8 BIOGRAPHICAL SKETCH. 
 
 him much,' and Dr. Johnson replied that "he had a 
 vanity in being thought easy;" Bishop Home wrote 
 his anonymous " Letter to A. Smith on the Life, 
 Death, and Philosophy of his friend D. Hume," and 
 Pratt replied to it; while John Wesley, in a sermon 
 preached some time after Hume's death, alluded to 
 his last days as described by Smith, and called upon 
 the dead man to say whether he had not learned 
 that 'it is a fearful thing to fall into the hands of the 
 living God.' Ne\ertheless, Adam Smith's estimate of 
 Hume's personal character is confirmed by the fact 
 that Campbell and Blair, both clergymen, and both 
 skilful opponents of his anti-theological arguments, 
 were among his personal friends, and by the testimony 
 of Francis Hardy, who says in his " Life of the Earl 
 of Charlemont": "Of all the philosophers of his sect, 
 none, I believe, ever joined more real benevolence 
 than my friend Hume. His love to mankind was 
 universal and vehement ; and there was no service he 
 would not cheerfully have done to his fellow-crea- 
 tures, excepting only that of suffering them to save 
 their souls in their own way." 
 
 Neither the Autobiography nor Adam Smith's letter 
 contains any reference to the celebrated ' quarrel ' 
 with Rousseau ; for Hume wished it forgotten, though 
 it did him no discredit. The story can be briefly told. 
 When the erratic and morbid author of the ' Emile ' 
 was in trouble on the Continent, Hume invited him to 
 England, found him a pleasant home, and got him the 
 offer of a pension. But one day Rousseau received a 
 letter inviting him to the court of King Frederick of 
 Prussia and promising that if he would go there he 
 
BIOGRAPHICAL SKETCH. IQ 
 
 would be given no opportunity to pose as a martyr. 
 Rousseau became much excited, remembered that 
 he had once heard Hume say in his sleep " I have 
 Jean Jacques Rousseau," and publicly accused him, 
 not only of writing the letter, but of bringing him to 
 England to betray him to his enemies. Hume was 
 persuaded to answer his accusations ; and thus the 
 controversy began. As a matter of fact the offending 
 letter was written by Horace Walpole, who despised 
 Rousseau. Of Hume himself Walpole wrote : "I am 
 no admirer of Hume. In conversation he was very 
 thick ; and I do believe hardly understood a subject 
 till he had written upon it." 
 
 Hume is buried on the outskirts of Edinburgh, and 
 his tombstone bears this inscription : 
 
 David Hume 
 Born 1711 Died 1776 
 
 Leaving it to Posterity to add liie Rest. 
 
SOURCES OF HUME'S SCEPTICAL 
 PHILOSOPHY. 
 
 The ' Treatise of Human Nature,' Hume's first 
 and greatest work, is connected in the closest pos- 
 sible way with the systems of Locke and Berkeley. 
 
 (i) Locke, in trying to show that all knowledge 
 depends upon experience, had thought it necessary 
 to prpve that all ideas, the elements of knowledge, 
 are derived from experience. He succeeded in doing 
 this to his own satisfaction, but only because he failed 
 to distinguish between pure sensations and their 
 revived images in memory and imagination on the one 
 hand, and these sense-images together with the closely 
 associated intellectual factors which enter into the 
 simplest act of knowledge on the other. For example, 
 he said that the idea of impenetrability is derived 
 from the sense of touch, and that if any one desires 
 to ascertain the content of this idea he may "'put a 
 flint or a football between his hands and then en- 
 deavor to join them, and he will know." Here 
 Locke did not distinguish from the mere muscular 
 and tactual sensations involved, the additional com- 
 plex thought that in spite of the effort made it is im- 
 possible to bring the hands together, because there 
 
 21 
 
22 SOURCES OF HUMES SCEPTICAL PHILOSOPHY. 
 
 is sometliing between them that resists extinction. 
 Yet it is clear that this thought is not a part of the 
 sensations involved, and that without it we could have 
 no idea of impenetrability. 
 
 (2) Berkeley accepted Locke's conclusion that all 
 the elements of knowledge are derived from sense- 
 experience, but he saw as Locke did not that sensa- 
 tions and their fainter reproductions consist simply of 
 images presented to some sense or other — of visual, 
 auditory, or tactual pictures, as it were. Berkeley 
 therefore supposed that all thought consists of nothing 
 but a series of simple or complex images. 
 
 (3) But every image is an image, not of a so-called 
 general idea, but of some particular thing, more or 
 less definitely conceived. We cannot, for example, 
 picture a triangle which is not either equilateral, isos- 
 celes, or scalene, nor imagine a taste which is neither 
 sweet, sour, saline, or the like. There are, therefore, 
 no abstract ideas, or ideas of things or qualities in 
 general. 
 
 (4) One idea especially, of which Locke spoke, 
 Berkeley could not picture : that, namely, of an inert, 
 senseless something called substance, which has all the 
 qualities perceived by the senses but is not any of 
 them. So he concluded that the only possible idea 
 of substance is the complex of ideas of the individual 
 qualities of a particular object as they present them- 
 selves to the human mind through the organs of sense; 
 and that, as the mind knows only these ideas, it is 
 illogical, unnecessary, and even absurd to assert the 
 existence of an absolutely unknown something called 
 substance, or matter, to account for these sensations. 
 
SOURCES OK HUMES SCEPTICAL PHILOSOPHY. 23 
 
 These four conclusions reached by Locke and 
 Berkeley — that all ideas are derived from experience, 
 that experience is only of individual mental images, 
 and that therefore there can be no abstract ideas, and ' 
 no idea of a substance which underlies the perceptible 
 qualities of things — these are the whole basis on which 
 Hume's system rests. 
 
BRIEF EXPOSITION OF HUME'S 
 PHILOSOPHY. 
 
 THE SYSTEM IN OUTLINE. 
 
 The First Part of the Treatise is concerned largely 
 with the four principles just enunciated. The omis- 
 sion of all reference to external reality from the defi- 
 nition of Impressions and Ideas is in accordance with 
 Berkeley's rejection of a material world ; and Sections 
 VI. and VII. are devoted to a reaffirmation of Berke- 
 ley's doctrines that there can be no idea of an under- 
 lying substance, and no abstract idea of anything. 
 
 In Part II. the principle that every idea is a definite 
 mental image is applied to the conceptions of space, 
 time, and existence. It is absurd to say that space is 
 infinitely divisible ; for we can picture neither an in- 
 finitesimal portion of space nor an infinite process of 
 division. The ideas of empty space and empty time are 
 equally impossible ; for experience always presents 
 space as a relation between the parts of visual or tac- 
 tual images, and time as a relation between successive 
 impressions and ideas; and it is impossible to form an 
 idea of the relation apart from that which is related. 
 In like manner, since there is no impression of exist- 
 ence or of external existence apart from that of the 
 
 25 
 
26 BRIEF EXPOSITION OF HUMe's PHILOSOPHY. 
 
 object or qualities existing, the idea of the one cannot 
 be abstracted from that of the other. Indeed, if by 
 external existence is meant something specifically dif- 
 ferent from impressions and ideas themselves, no 
 real conception of it can be formed at all ; for all 
 thought is confined to impressions and ideas, that is, 
 to more or less vivid mental images. 
 
 In Part III. two topics are treated together: infer- 
 ence and the idea of causation. By separating them 
 we can perhaps make Hume's conception of each a 
 little clearer than is otherwise possible. 
 
 First of all, inference. — Of Hume's seven Philosoph- 
 ical Relations or categories, of resemblaiice, proportions 
 in quantity and number, degrees of any quality, contra- 
 riety, identity, situation in time or place, and causation, 
 the first four — corresponding to Kant's mathematical 
 relations — are concerned with mental images as mere 
 images, and are always the same for the same images. 
 They are therefore the objects of intuitive and de- 
 monstrative knowledge. The three others, however, 
 correspond to Kant's dynamical relations and are con- 
 cerned with facts and events considered as really 
 existing or happening, not merely with the inner rela- 
 tions of any set of mental pictures. And as we can- 
 not predict the order of nature by merely analyzing 
 our conceptions, these relations are not the objects 
 of either intuitive or demonstrative knowledge, i.e., of 
 knowledge proper. Nevertheless, through one of 
 them, namely, through the relation of causation, 
 something can be inferred about events that are not 
 directly perceived through any sense. And the ques- 
 tion is : How is this possible ? 
 
BRIEF EXPOSITION OP HUMe's PHILOSOPHY. 27 
 
 To infer is to pass in thought from some object or 
 fact perceived or remembered to some other object 
 or fact not experienced, and on the basis of the former 
 to believe in the existence of the latter. 
 
 It has been shown already that there is no idea of 
 existence apart from the idea or image of the object 
 existing. A little introspection will show just as 
 clearly that the belief in an object's existence adds no 
 new image to that of the object already formed. 
 And certainly belief does not change the outline or 
 color of that image ; for then the image would repre- 
 sent, not the same, but some other object. The only 
 possible difference, therefore, between the mental 
 image of something believed and the image of the 
 same thing not believed must be a difference of vivac- 
 ity or intensity. And beyond the image with its out- 
 li.ne, color, and vivacity, thought there is none. Be- 
 lief therefore consists merely in the vivacity of a 
 mental image. 
 
 There are thiee Natural Relations, or principles of 
 association, between objects, which tend to convey 
 the thought from the impression or idea of the one 
 to the idea of the other. And, moreover, when the 
 thought is conveyed by any of these principles from 
 an impression of sense or a vivid image in the mem- 
 ory to an idea, the preceding vivid image of sense or 
 memory imparts some of its vivacity to the suggested 
 idea ; so that this idea is much more vividly pictured 
 than if it had been called up by some idea of the im- 
 agination only. 
 
 These natural relations are Resemblance, Contiguity, 
 and Causation. But Causation is much more effective 
 
28 BRIEF EXPOSITION OF HUME S PHILOSOPHY. 
 
 than either of the others, and imparts a much greater 
 degree of vivacity to the associated idea. 
 
 This is because objects which we recognize as 
 causes and effects are not only always successive and 
 contiguous to each other in space and time, but they 
 have been constantly conjoined in our experience, so 
 that the association between them is very fixed and 
 unerring. 
 
 Indeed the association is so strong that all the vi- 
 vacity of belief is conveyed to the suggested image. 
 And thus it is that through causation an inference is 
 drawn to something beyond present experience. 
 
 Conclusions regarded as vatxeX^ probable are reached 
 either when one's experience of the cause and its ef- 
 fect has been too limited to produce a well-established 
 association between them, or when the same cause has 
 been connected in one's experience with various ef- 
 fects. In the latter case the impression of the cause 
 tends to suggest the ideas of all the effects; but only 
 one of the images can be present at a time; there is 
 therefore a conflict between them; and when finally 
 the strongest has crowded out the others, it has lost 
 much of its vivacity, so the belief attached to it is but 
 faint, and the conclusion is said to be only probable. 
 
 Another kind of probability is attained by analogy. 
 In this case the present impression is not a perfect re- 
 production of the cause which has always been expe- 
 rienced in connection with a certain effect, though it 
 resembles it more or less; and the lack of a perfect 
 resemblance diminishes the vivacity of the suggested 
 image, as did the lack of a perfect experience in the 
 other kind of merely probable inferences. 
 
BRIEF EXPOSITION OF HUMe's PHILOSOPHY. 29 
 
 As the Strength of an association can vary indefi- 
 nitely, and as there can also be any degree of resem- 
 blance between the present impression and a cause 
 given in past experience, it is evident that an inference 
 from a present impression to its anticipated effect may 
 involve any degree of belief, from the merest proba- 
 bility to the fullest conviction. But in every case the 
 inference is a matter of imagination, and not of rea- 
 soning. For, did the inference from past to future | 
 depend upon reasoning, the uniformity of nature 
 would have to be the major premise. And what rea- 
 soning could ever prove this premise ? It cannot be 
 demonstrated, for there is no contradiction in suppos- 
 ing the course of nature to change; and in every at- 
 tempt to prove it by induction it is merely assumed. 
 
 Since the causal relation is so important for infer- 
 ence as to matters of fact, its nature should be deter- 
 mined a little more accurately. Causes and effects 
 are not only successive and contiguous and constantly 
 conjoined in our experience, but we suppose a certain 
 necessary connection to exist between them; and the 
 idea of this necessary connection is much more ob- 
 scure than that of succession, of contiguity, or of con- 
 stant conjunction. To clear it up it is necessary to 
 find the impression from which it is derived; for, 
 since there are no innate ideas, there must be such an 
 impression, and impressions are intenser than their 
 ideas, and their outlines are therefore clearer. 
 
 Though contiguity and succession between external 
 objects can be perceived, none of the senses present 
 any image of their connection. The impression is 
 therefore not gained from a contemplation of nature. 
 
30 BRIEF EXPOSITION OF HUMe's PHILOSOPHV. 
 
 as Locke said in his chapter on Power. Much less can 
 it be derived from the ' substantial forms ' or other 
 unintelligible properties of matter, or even from the 
 Divine activity; for none of these are objects of per- 
 ception, and none of them therefore can afford an im- 
 pression. 
 
 Nor can it be gained from the known influence of 
 volition upon the organs of the body; for we are no- 
 where directly conscious of this influence, as is proved 
 by the fact that it is generally supposed to be direct, 
 while in reality it is exerted only through the nerves 
 and muscles. Nor, again, is the idea of necessary 
 connection obtained by observing the control of the 
 will over tlie course of one's own ideas; for the greatest 
 voluntary effort is often accompanied with the least 
 control. 
 
 Finally, it is of no avail to say that the idea is ab- 
 stract; for abstract ideas are but particular aspects of 
 ordinary ideas, and must therefore have been pre- 
 ceded by impressions like the rest. 
 
 The impression is obtained, however, from the mu- 
 tual relations of associated ideas when one suggests 
 another; for, like the relations of resemblance, pro- 
 portion, degree, and contrariety, tlie connection be- 
 tween ideas becomes present to consciousness with 
 the ideas themselves, and can be obtained by a simple 
 inspection or 'comparison ' of them. 
 
 The impression of necessary connection or power is 
 therefore the impression of a certain relation between 
 ideas, namely, of connected ideas suggesting each 
 other. And the idea of necessary connection also 
 must be the idea of such a relation between ideas; for 
 
BRIEF EXPOSITION OF HUME's PHILOSOPHY. 3I 
 
 the idea is a copy of the impression, and it is impossi- 
 ble to abstract the idea of the relation from that of 
 the ideas related. In other words, the idea of neces-i 
 sary connection is a pair of associated mental images 
 considered in reference to their connection with each 
 other. 
 
 This being so, it is absurd to speak of a connection 
 between external objects; and causation therefore 
 consists of contiguity, succession, and constant con- 
 junction in nature, together with a pair of connected 
 ideas (and therefore the idea of connection) in the 
 mind of the observer. So the causal relation is a 
 mixed one, partly independent of mind and partly 
 dependent upon it. 
 
 The common belief that there is a necessity in 
 things themselves is the result of the mind's anthropo- 
 morphic tendency to ' spread itself ' over inanimate 
 objects and attribute to them its own ideas and 
 emotions. It is the same kind of confusion that leads 
 us to attribute to and at the same time deny of change- 
 less things the changes that really take place in our 
 own thought, and so to say that these things endure. 
 
 This doctrine of Causation can be applied as well 
 to our fellow-men as to nature. The sequence and 
 constant conjunction of motive and act is in them ; 
 the idea of their connection, in us. 
 
 It has thus been explained " why we conclude that 
 such particular causes must necessarily have such par- 
 ticular effects, and why we form an inference from 
 one to the other." As for the other question (Sec- 
 tions III. and IV.), " For what reason we pronounce 
 it necessary that everything whose existence has a be- 
 
3:; BRIEF EXPOSIIION OF HUMe'S PHILOSOPHY. 
 
 ginning should also have a cause ? "—no such neces- 
 sity exists, and every attempt to prove it has failed ; 
 for necessity is to be found only when objects have 
 been experienced in close conjunction and succes- 
 sion and their ideas have been associated. But we 
 pronounce it necessary because we draw a hasty in- 
 duction from those cases in which a necessity really 
 is involved. 
 
 In Part III. Hume tried to show that inference 
 concerning matters of fact not yet observed was a 
 matter of imagination, not of reasoning. In Part IV. 
 he attempts to do the same thing for demonstration 
 concerning the relations of ideas. 
 
 In all the demonstrative sciences occasional mis- 
 takes are made. In even a simple arithmetical addi- 
 tion oui faculties sometimes play us false. Knowing 
 this, we ought to add to any reasoning of this sort 
 a second judgment pronouncing upon the probable 
 correctness of the first. But this judgment itself may 
 be erroneous ; so it also should be corrected by a 
 third ; and so on ad infinitum, when none of the orig- 
 inal assurance will be left. This is the result that 
 Reason would reach were it to determine our belief. 
 It is avoided only because the Imagination is too 
 sluggish to call up the appropriate images when the 
 train of ideas gets more than a very few steps from 
 the impression that started it. So, by keeping the 
 thought closely confined to present impressions and 
 the ideas most immediately associated with them, 
 imagination gives an assurance which reason, if al- 
 lowed its way, would utterly destroy. 
 
BRIEF EXPOSITION OF HUME S PHILOSOPHY. 33 
 
 Thus all belief is a matter of sense and imagina- 
 I tion and not of reasoning. 
 
 The next topic is Real Being, and it can be consid- 
 ered under two heads : I. Tilings external or bodies, 
 and II. Things internal or souls. 
 
 I. Body. — To ask whether external things exist or 
 not is useless , for believe in them we must ; and the 
 only question is, why 1 
 
 As it is impossible to form a mental image of 
 anything specifically different from impressions and 
 ideas, the conception of external things can be noth- 
 ing more than that of certain perceptions possessed 
 of a continuous existence independent of any per- 
 ceiving mind. To account for the belief in such 
 things it is necessary to consider the continuity and 
 the independence separately. 
 
 A. The continued existence which the imagination 
 attributes to certain perceptions is due to their pe- 
 culiar (i) coherence and (2) constancy. 
 
 (1) The Coherence of Impressions. — When there is 
 an established relation of contiguity and succession 
 between dissimilar impressions, the presence of the 
 one leads to the idea and expectation of the other, and 
 we get into the way of looking for this uniform se- 
 quence even when we have no impression of it. But 
 in order to find it we have sometimes to suppose 
 that a perception exists when not present to con- 
 sciousness. Thus when we perceive wood in the fire- 
 place before leaving a room and return to find only 
 ashes, the force of habit compels us to imagine the 
 burning fire as intervening. This necessity never 
 
34 BRIEF EXPOSITION OF HUMe's PHILOSOPHV. 
 
 arises, however, in the case of the passions ; for their 
 effects never appear unless they themselves have been 
 present to consciousness. 
 
 (2) The Constancy of certain impressions leads to 
 the same result. For when similar impressions con- 
 stantly recur the shock of surprise finally disappears, 
 and the passage from one such impression to another 
 is felt scarcely more than the passage from one 
 moment of a continuous jierception to the next. 
 Both kinds of experience therefore give rise to the 
 same easy feeling ; and or. this account they become 
 confused, and we tend to regard the recurring impres- 
 sions as really continuous and identical. 
 
 B. This leads to the belief in an existence of per- 
 ceptions independent of the mind. For, in spite of 
 this tendency of the imagination to regard recurring 
 impressions as continuous and identical, Reason still 
 insists that they are interrupted and different. To 
 reconcile the contradiction we therefore suppose two 
 sets of perceptions, the one interrupted and depend- 
 ent upon the mind that perceives them, the other 
 continuous and independent. The latter we now 
 distinguish by the name Objects, reserving the term 
 Perceptions for the former. 
 
 Thus the idea of an external world of objects and 
 the belief in it rest upon unjustifiable yet unavoidable 
 confusions and contradictions of imagination. 
 
 II. Souls. — To speak of perceptions apart from a 
 preceiving mind is not self-contradictory. For as an 
 external object is nothing more than an aggregate of 
 qualities, so a mind is nothing more than an aggregate 
 of perceptions ; and a perception can be said to be 
 
BRIEF EXPOSITION OF HUME's PHILOSOPHV. 35 
 
 present in a mind only in the sense that it is at the 
 moment associated with the special group of per- 
 ceptions of which that particular mind is made up. 
 This is why all discussions about the materiality or 
 immateriality of the soul are so meaningless. They 
 are attempts to describe the nature of an assumed 
 substance underlying all perceptions. But of such a 
 substance we can have neither impression nor idea. 
 It is therefore nonsense to attempt to describe it or 
 even to affirm its existence. 
 
 Though some specially favored metaphysicians may 
 be continually conscious of a perfectly identical and 
 simple Self, the rest of mankind, when they enter 
 most intimately into what they call themselves, can 
 find only a collection of rapidly-varying perceptions, 
 which, however, are bound together so firmly by 
 association that they are often supposed to be a unity, 
 simple and identical. 
 
 As to the relation between matter and mind, it is 
 through experience alone that any knowledge or idea 
 of the causal relation is gained ; and so it cannot be 
 maintained a priori, as the followers of Descartes main- 
 tain, that motion cannot cause perceptions, nor per- 
 ceptions motion. 
 
 The investigation of Human Nature was under- 
 taken in the hope that through a knowledge of its 
 principles a foundation for all the sciences could be 
 laid. But these principles have been found to lead to 
 such absurdities and contradictions that no conclu- 
 sions reached by their aid can be relied upon ; and 
 yet without them there can be no knowledge at all. 
 
2,6 BRIEF EXPOSITION OF HUME's PHILOSOPHY. 
 
 Total scepticism is therefore the only resort — and 
 that is impossible. 
 
 CAUSATION. 
 
 Hume's doctrine of causation is the most im- 
 portant and at the same time the most difficult part of 
 his whole philosophy. It has been often said that 
 Hume denied that any idea of necessary connec- 
 tion is possible, and that he reduced causation to 
 mere uniform sequence. But Hume himself in the 
 chapter devoted to the subject expressly stated, and 
 emphasized the statement, that the idea of necessary 
 connection does enter into the conception of causa- 
 tion, and that it must be accounted for. All that he 
 denied was that the idea can be accounted for in the 
 way in which he believed various authors had attempted 
 to account for it, and that it can be applied as these 
 writers would apply it. " Necessity is nothing but an ; 
 internal impression of the mind or a determination to 
 pass from one object to its usual attendant,"* and a 
 necessary connection between anything but thoughts/ 
 cannot be conceived : this is the whole burden of the 
 most difficult section in the Treatise. 
 
 But here a difficulty presents itself : how can Hume 
 treat the mind's necessity to pass from one idea to 
 another as identical with the impression or obser- 
 vation of that necessity ? Certainly the two are not 
 identical ; but unless they be regarded as such the 
 one can no more explain the other than the connec- 
 
 * Pp. 126, 1. i; 125, 1. 23. See also 112, 1. 28. 
 
BRIEF EXPOSITION OF HUME's PHILOSOPHY. 37 
 
 tion between an act of will and its result can explain 
 the knowledge of the connection. 
 
 A similar difficulty is found in Hume's account of 
 the cause of the association from which this idea of 
 necessity is derived. Does the association of ideas' 
 result from the mere fact that similar combinations of 
 objects frequently recur, or from the observation of the 
 fact ? There are at least half a dozen passages in 
 which he says, " the observation of this resemblance " * 
 between several instances causes the association ; 
 while in others he speaks only of the resemblance 
 itself. It is true that in ordinary experience it is the\ 
 observation of a constant conjunction between phe- 
 nomena which leads to the supposition of a causal 
 connection between them. But for Hume's 'infer- 
 ence ' this observation is not necessary ; for a repeated 
 experience of conjoined phenomena is sufficient to es- 
 tablish an association between them whether the fact 
 of the repeated conjunction has been observed or not. 
 
 Another question which arises in this connection 
 is whether Hume regarded the internal necessity to 
 which repeated experience gives rise as a " determina- 
 tion of the mind " by an impression or idea, or simply 
 as a determination of one idea by another. 
 
 To explain these difficulties it is necessary to con- 
 sider Hume's doctrines in their historical connection. 
 The plain people regard not only things, but the rela- 
 tions between them, as perceived immediately, and 
 from this natural realism of common-sense thought 
 passes but slowly. It may be discovered, for example, 
 
 *Pp. 125-127. 
 
38 BRIEF EXPOSITION OF HUME's PHILOSOPHY. 
 
 that no causal connection can be observed between 
 things, while it is still taken for granted that the 
 things themselves and their other relations are im- 
 mediately known. Or it may be discovered that 
 thought is not a copy of things, while it is still as- 
 sumed that it is caused by them ; and then the con- 
 ception of a Ding an sick or an unknowable arises. 
 And even when such ways of thinking are declared to 
 be erroneous there is a continual tendency to revert to 
 them. In the age in which Hume lived this influence 
 of avowedly abandoned modes of thought was ex- 
 emplified in the conception of ideas. That things 
 cannot be immediately known was recognized, be- 
 cause it had been found that there is no direct causal 
 relation between extra-bodily objects and the mind. 
 The problem was to restore this immediate relation 
 between the mind and the object known ; and since 
 the mind did not go out to things, it was assumed 
 that things came in to the mind, — not themselves, how- 
 ever, but through their representatives, called ideas, 
 which were supposed to be conveyed in some way 
 or other by the senses to the mind. Thus, something 
 was got into the immediate presence of the mind ; 
 and perception was explained. 
 
 How these ideas could be perceived when brought 
 ' into ' or ' before ' the mind no one asked ; but it was 
 taken for granted that the mind could perceive ideas 
 and their relations just as easily and just as completely 
 as the most naive realist supposed he could perceive 
 things. Except that ideas had been substituted for 
 things, the standpoint of the philosophers was essen- 
 tially that of the plain people. The only problem was 
 
BRIEF EXPOSITION OF HUME S PHILOSOPHY. 39 
 
 to account for the presence of the ideas ; and this 
 came to be regarded as a very grave problem indeed, 
 for the philosophers were still influenced a good deal 
 by the common forms of speech, and were only too 
 apt to regard bothddeas and the physical motion that 
 causes them as shadowy entities which could 'inhere ' 
 in mind or in matter, and be ' imparted,' ' communi- 
 cated,' or ' conveyed ' from one thing capable of ' pos- 
 sessing ' them to another. Now when the Cartesians ' 
 discovered that the essence of the mind is thought 
 and the essence of matter extension, and that ideas 
 cannot exist in things, nor motion in minds ; how is it 
 possible, they asked, for any communication to take 
 place between matter and mind, unless in passing from ; 
 the one to the other motion becomes thought, and j 
 vice versa''. And this seemed to them equally impos- ■ 
 sible, for "matter and motion are still matter and mo- 
 tion, and 'tis absurd to imagine that the shocking of 
 two globular particles should become a sensation of 
 pain and that the meeting of two triangular ones 
 should afford a pleasure." * 
 
 When they had avoided this difficulty and accounted 
 for the presence of ideas in the mind by the Occasion- 
 alistic hypothesis, the Cartesians supposed they had 
 explained perception, just as Berkeley thought he had 
 explained it by his similar supposition that ideas are 
 given by God. Hume, with his conception of causa- ^ 
 tion, was able to avoid the Cartesian puzzle about 
 the interaction of mind and matter ; and yet, like his 
 predecessors, he failed to see the real difficulty con- 
 
 * Treatise, Part IV., Sec. V. 
 
40 BRIEF EXPOSITION OF HUAIE S PHILOSOPHY. 
 
 nected with the ordinary conception of perception, and 
 took it for granted that he had accounted for'id€«s*of 
 color and extension when he had supposed that there 
 were colored and extended ideas before the mind, and 
 that when he had shown how ideas are related he had 
 explained the idea of their relation. 
 
 With this point of view, it was as natural that Hume 
 should fail to distinguish between the connection of 
 ideas and the impression of their connection, and 
 between their repetition and the observation of the 
 repetition, as it was that Locke should overlook the 
 distinction between the fact that observed qualities 
 and substances receive their existence from the ap- 
 plication and operation of some other observed being, 
 and the knowledge of that fact.* And to make this 
 part of his doctrine consistent it must be supposed 
 that the 'determination ' Hume spoke of was a deter- 
 mination of ideas, and that he used the word 'mind' 
 only loosely and provisionally. 
 
 Thus it was that Hume reduced necessary connec- 
 tion, the most objective of all dynamical relations, to 
 a mere relation of ideas, perceived immediately with 
 the ideas themselves. But, notwithstanding the fact 
 that he had accepted the philosophical explanation of 
 perception through ideas, throughout his whole ac- 
 count of causation he took it for granted that things 
 with their contiguity, succession, and constant con- 
 junction can be perceived directly; and from this 
 strange combination of half-critical and wholly non- 
 critical thought there resulted the mixture of phenom- 
 
 * Essay, Book II., Chap. XXVI., Sec. I. 
 
BRIEF EXPOSITION OF HUMES PHILOSOPHY. 41 
 
 enalism and naive realism which is found in his 
 second defini«ition of a cause. 
 
 Though Hume professed to have no idea of cau- 
 sation but that of two objects frequently perceived 
 in close succession and the idea of one of them sug- 
 gesting that of the other, to account for this sug- 
 gestion of one idea by another it was necessary for 
 him to assume causal relations independent of it. 
 Such was the relation between things contiguous and 
 successive and the perceptions they produce; such 
 was that between repeated perceptions and the ' habit ' 
 of mind which accounts for individual suggestions; 
 such was the ' natural ' relation of causation, if Hume 
 meant to distinguish it from contiguity as a cause of 
 association; and such must be the relation between 
 any 'hidden cause' and its effect. It is this kind of 
 causation which he quietly assumed, rather than that 
 which he defined, that corresponds to the ordinary 
 conception of a cause. But Hume had said that the 
 ordinary conception is really impossible. What he 
 accomplished, therefore, was this: by repeatedly as- 
 suming a causation of which he said it was impossible 
 to conceive, he accounted for a conception of a cause 
 that no one ever really held. 
 
 The nature of the connection involved is not the 
 only respect in which the causes Hume assumed to 
 exist are different from those he defined. His whole 
 account of the idea of causation depended upon the 
 'observation ' that causes and effects are always 
 closely conjoined in time; and yet when he said that 
 every idea is caused by a previous perception resem- 
 bling it, he assumed that causes and effects are sim- 
 
42 BRIEF EXPOSITION OF HUME'S PHILOSOPHY. 
 
 ilar, rather than that they are always to be found 
 together. Certainly it is impossible that 'ideas of the 
 imagination ' can be constantly conjoined with their 
 corresponding impressions, when they occur, as Hume 
 says, in an entirely different order.* 
 
 How far Hume's rules by which to judge of causes 
 and effects are consistent with the doctrine that " any- 
 thing may produce anything" ; how many of them are 
 the logical consequences of his conception of a cause; 
 and how many of them would actually result from the 
 principles of the imagination th\t Hume supposed 
 to explain the idea of a cause, cannot be discussed 
 here. 
 
 Hume's theory of causation is no more satisfactory 
 when applied to the will than when applied to things; 
 for the real problem is, not whether the spectator 
 feels any inner necessity to pass from one idea to 
 another, but whether the agent is under any neces- 
 sity to pass from his idea to his act. 
 
 THE CONCEPTION OF REALITY. 
 
 Hume's account of the idea of causation would have 
 been less plausible if his conception of reality had 
 been less pliable. 
 
 At the beginning of the Treatise he assumed that 
 impressions ' arise in the soul originally from unknown 
 and perfectly inexplicable causes.' f As he advanced 
 towards his chapter on the idea of necessary connec- 
 tion he substituted for this unknowable thing in itself 
 
 * Part I., Sees. I., II., and III. 
 
 t Part I., Sec. II., and Part III., Sec. V. 
 
SrIef Exl>oSiTiON Op Hume's philosophv. 43 
 
 ' objects ' which could be observed to be frequently 
 conjoined in time and place, but which could not be 
 observed or even thought to be connected. And be- 
 fore the chapter was ended he found it necessary to 
 join the plain people and assume the knowledge of a 
 'nature ' full of connections. 
 
 Having accounted for the idea of necessary con- 
 nection by means of this assumption and arrived at 
 his semi-realistic and semi-idealistic conception of a 
 cause, as " an object precedent and contiguous to 
 another, and so united with it that the idea of the 
 one determines the mind to form the idea of the 
 other," etc., Hume remembered that causation was a 
 relation, and that according to his definition rela- 
 tions exist between ideas, not- things, and- so he iden- 
 tified his objects with ideas by adding that a cause 
 may be considered " either as a comparison of two 
 ideas or as an association betwixt them." This over- 
 turned his account of the idea of connection ; but 
 it enabled him to return to the idealism which he 
 formally recognized, and it prepared the way for his 
 forthcoming account of the idea of real external 
 things. 
 
 Real things can act and be acted upon ; while 
 mental images are mere transient states of a perceiv- 
 ing subject and can do or suffer nothing. Such images 
 are the perceptions with which the Treatise opened. 
 But when Hume remembered that his ' objects ' were 
 perceptions he still regarded them as possessed of all 
 the properties of real things ; though, of course, they 
 were immediately present to consciousness, since they 
 were perceptions. This made it seem easy to account 
 
44 BRIEF EXPOSITION OF HUME's PHILOSOPHY. 
 
 for the idea of a set of permanent perceptions, called 
 things. 
 
 But it is not, as Hume said, the perceptions them- 
 selves that the vulgar believe to have a continued 
 existence, but rather the efficient things of which 
 Hume's perceptions were after all but lifeless models. 
 And the philosophers believe, not in a second set of 
 perceptions, but in the same things as the vulgar. 
 But the philosophers realize that they know these 
 things only through their own mental images, and so 
 they suppose there are three facts ■ the thing, the 
 image of it, and the mind knowing the thing by per- 
 ceiving the image ; while the vulgar are so busily con- 
 cerned with the things themselves that it never occurs 
 to them that any image intervenes between the things 
 and their knowledge of them. For them, therefore, 
 there are but two facts : the thing and the mind 
 knowing it. For Hume also there were two facts ; and 
 this is why he identified his 'objects' with those of 
 the vulgar. But Hume's facts were the image and 
 the mind knowing it; and an image is not a thing. 
 
 Both Hume and Kant started with the assumption 
 that perceptions are caused by a thing in itself, pos- 
 sessed of all the extra-mental reality that the plain 
 people believe things to have ; and when they came 
 to account for the conception of reality, what they 
 both explained was not the idea of the transcenden- 
 tal things which they and the plain people had alike 
 assumed to exist ; but it was the idea of some phe- 
 nomenal 'permanent in perception,' the conception 
 of which had been developed in the course of their 
 philosophy. 
 
BRIEF EXPOSITION OF HUMES PHILOSOPHY. 45 
 
 Though at this stage of his philosophy Huine sup- 
 posed his conceptions to be those of the plain people, 
 there could be no doubt about the next ; for having 
 made all the use that was necessary of the popular 
 assumption of a mind capable of forming habits and 
 perceiving what is presented to it, Hume proceeded 
 to show that this assumption is just as impossible as 
 is the idea of an external substance, and that the per- 
 ceptions themselves are the only reality. These self- 
 existent perceptions he supposed, presumably, not only 
 to know themselves, but to have a share in the knowl- 
 edge of any other images with which they might be- 
 come associated. How the group of perceptions 
 which he made to constitute a mind is to be distin- 
 guished from the group which constitutes a thing, or 
 whether there is any distinction between them, Hume 
 did not say. 
 
 THE BELIEF IN REALITY. 
 
 When Hume tried to show how the belief in the in- 
 dependent existence of ' objects ' resulted from the 
 belief in the permanence of perceptions he reversed 
 the natural order. For people are realists before they 
 are idealists ; and the earliest perceptions that we know 
 anything about already carry with them a reference to 
 something which they claim to represent. AVhen we 
 make use of the conception of a coherent order of 
 nature, it is not to prove that most perceptions really 
 do represent reality, but to show tliat some of them 
 do not; for any particular perception can be shown to 
 be an illusion only if a great many others with which 
 
46 BRIEF EXPOSITIOX OF HUMe's PHILOSOPHV. 
 
 it does not cohere are already believed to represent 
 reality. 
 
 In his section on Scepticism with regard to the 
 Senses Hume proved that from mere subjective images 
 there can be no logical inference to any reality be- 
 yond them. This is true. But, since the given men- 
 tal facts, though subjective, are more than mere 
 images, belief in extra-mental things does not involve 
 all the absurdities that Hume supposed. That this 
 belief cannot be proved to be correct is no reason 
 that we should accept it unwillingly ; for all reasoning 
 must be based on premises which are accepted, not 
 proved. Whether these premises rest upon the 
 imagination, as Hume supposed, or whether they 
 have a much deeper root in the whole mind and life, is 
 a matter of indifference so Jong as they are necessary. 
 Hume especially had no right to profess uneasiness 
 at the thought that belief rested ultimately upon the 
 imagination ; for he had resolved all thinking into 
 imagining. And he had no right to ask whether 
 he should accept the suggestions of tlie more or of 
 the less general principles of the imagination, or 
 to hesitate because these suggestions were contra- 
 dictory ; for to him all conviction was a matter of 
 necessity, and choice he had none. 
 
 CONFIDENCE IN REASON. 
 
 Hume's proof that logically reason should not be 
 trusted rests upon an obvious fallacy. Granting that 
 every judgment should be tested by another, and that 
 each one would weaken the confidence reposed in that 
 
BRIEF EXPOSITION OF HUMES PHILOSOPHY. 47 
 
 preceding it, it does not follow that all the original 
 conviction would be finally destroyed; for, in weaken- 
 ing the conviction attached to the second judgment, 
 the third strengthens that belonging to the first : 1 — 
 (1^ — i) — I, not i, as Hume's argument supposes ; 
 and the sura of the series is two thirds, not zero. The 
 truth is that every judgment carries conviction with 
 it; and if to make an error proves reason's weakness, 
 to detect it proves its strength. 
 
 Though Hume failed to prove the untrustworthi- 
 ness of reasoning, and though he was wrong in mak- 
 ing belief nothing more than the vivacity of impres- 
 sions, he was right in maintaining, in an age where 
 mathematical demonstration was regarded as the 
 highest type of thought, that much demonstrative 
 reasoning carries with it less assurance than may 
 often be attained in other ways. It is intense sensa- 
 tions, strong feelings, and vigorous action that produce 
 the deepest convictions. 
 
 INFERENCE. 
 
 When Hume accepted the view that all thought 
 could be resolved into imagination, it naturally fol- 
 lowed that the only test of truth which he could 
 accept was conceivability ; and the only inference, 
 the passing of thought from one image to another. 
 But though it is necessary that a conclusion be 
 suggested in order that it be thought of at all, the 
 mere passing in thought from one image to another 
 is not sufficient to constitute inference. For, while 
 fundamental beliefs are merely caused, and not 
 
48 BRIEF EXPOSITION OF HUME's PHILOSOPHY. 
 
 proved, inferences are conclusions thought to be 
 warranted by the evidence. And causation is impor- 
 tant for inference, because conclusions based upon the 
 law of causation are thought to be warranted by what 
 is known of the objectively fixed order of events 
 which causation implies. 
 
 Even if the association of ideas could account, as 
 Hume supposed, for the inference from causes to 
 effects, it could not account for the inference from 
 effects to causes ; for when the order of ideas is to 
 be reversed mere contiguity and succession form but 
 a poor bond between them, and do not convey much 
 ' vivacity ' from one to another, as we learn when we 
 try to say the alphabet backwards. Moreover, when 
 inference and causation are both resolved into the 
 association of ideas, the one cannot be said to be 
 either warranted or caused by the other, for they have 
 become indistinguishable. And, finally, were there 
 no reality beyond themselves to which perceptions 
 refer, there could be no distinction between true and 
 false perceptions; and none between valid and invalid, 
 warranted and unwarranted, inferences. 
 . In his account of inference, therefore, as in his 
 ■account of the ideas of causation and reality, Hume 
 made no attempt to explain what is most important. 
 But he did one great thing : he proved that the belief 
 in the uniformity of nature, without which neither 
 science nor work would be possible, rests upon causes 
 and not upon proofs. And thus he emphasized the 
 great part played by faith in every sphere of life. 
 
BRIEF EXPOSITION OF HUME S PHILOSOPHY. 49 
 
 THE TREATISE AND THE ENQUIRY. 
 
 The foregoing introductory paragraphs have had 
 reference to the Treatise of Human Nature rather 
 than to the Enquiry concerning Human Understand- 
 ing, and the extracts to follow have been taken from 
 the same vifork. There is, however, considerable 
 difference between the two books. 
 
 The Treatise was written when Hume's enthusiasm 
 for philosophy had received no check, and it is 
 characterized by the keenest observation of psycho- 
 logical facts and by a relentless logic, however para- 
 doxical the conclusions to which that logic leads. 
 The very confusion which often makes it so difficult 
 to follow the argument is due to Hume's desire to 
 overlook no difficulty and to leave the origin of no 
 idea unexplained, however absurd that idea may be. 
 
 The Enquiry, on the other hand, was written after 
 the bitterly disappointing reception given the Treatise 
 had quenched much of Hume's zeal for philosophy 
 and driven him to work in other fields of literature. 
 Having learned there to gauge the popular taste, 
 Hume recast parts of the Treatise in essay form, and 
 published them in the various Enquiries. But now 
 not only was he addressing a popular audience, but he 
 had lost enthusiasm for his subject, and the Enquiry 
 concerning Human Understanding suggests more 
 than a suspicion that Hume's interest in it was more 
 anti-theological than psychological. The introduction 
 speaks, not of the foundation to be laid for all the 
 sciences by the study of human nature, but of popu- 
 
50 BRIEF EXPOSITION OF HUMe's PHILOSOPHY. 
 
 lar superstitions to be driven from their shelter 
 among the bramble-, of metaphysics, sections taken 
 from the Treatise are modified so as to state, not only 
 that certain philosophers are unable to explain the 
 origin of certain ideas, but that they ' diminish in- 
 stead of magnifying the grandeur of those attributes 
 of the Creator which they affect so much to cele- 
 brate,' and to speak of "dogmas invented on pur- 
 pose to tame and subdue the rebellious reason of 
 mankind"; and in the Enquiry entirely new sections 
 on Miracles and a Particular Providence and a Future 
 State are introduced. All the difficult parts of the 
 Treatise in which Hume had attempted to account 
 for the apparent existence of ideas which he regarded 
 as impossible are omitted from the Enquiry ; so that 
 its work is purely destructive. And instead of hon- 
 estly following even such reasoning as was allowed to 
 remain to its logical conclusion, and exposing himself, 
 as he had said in the Treatise, " to the enmity of all 
 metaphysicians, logicians, mathematicians, and even 
 theologians," by discrediting all knowledge and all 
 science, Hume distinguished in the Enquiry between 
 the excessive scepticism to which his principles logi- 
 cally lead and a more mitigated scepticism ; and by 
 adopting the latter, he rescued books of ' abstract rea- 
 soning concerning quantity and number and of ex- 
 perimental reasoning concerning matter of fact and 
 existence ' from the flames to which all the other vol- 
 umes in one's library were to be condemned as con- 
 taining nothing but sophistry and illusion. And this 
 in spite of the fact that in the very same section not 
 only had he made use of the ' paradoxical conclusions 
 
BRIEF EXPOSITION OF HUMES PHILOSOPHY. 51 
 
 of geometry or the science of quantity, big with con- 
 tradiction and absurdity,' as an argument against " all 
 abstract reasonings " ; but had made the sceptic to 
 insist justly " that all our evidence for any matter of 
 fact which lies beyond the testimony of sense or 
 memory " rests ultimately upon nothing more than 
 "custom or a certain instinct of our nature, which is 
 indeed difficult to resist, but which, like other in- 
 stincts, may be fallacious and deceitful." 
 
 In short, though in style the Enquiry "exhibits 
 a great improvement on the Treatise ", Professor 
 Huxley is right in saying that the substance "is cer- 
 tainly not improved." What is new is out of place in 
 a psychological study, and the changes made in what 
 is old indicate pretty plainly that the earnest critical 
 thinker of the Treatise had acquired many character- 
 istics of the mere sophist. 
 
 Parts of the ' Treatise ' ?iot Represented in the ''Enquiry.' 
 Part I. 
 
 Sec. 2. Distinction between Impressions of Sensa- 
 tion and of Reflection. 
 
 " 3. Distinction between Memory and Imagina- 
 tion. 
 
 " 5. Distinction between Natural and Philoso- 
 phical Relations. Enumeration of the 
 Philosophical Relations or Categories. 
 
 " 6. The Ideas of Mode and Substance. 
 
 " 7. ' Of Abstract Ideas.' (Represented by only 
 ten lines and a note in Sec, XII. of the 
 Enquiry.) 
 
52 BRIEF EXPOSITION OF HUMe's PHILOSOPHY. 
 
 Part II. 
 
 Sees. 1-5. Space and Time. (Represented by only 
 a page and a half in Sec. XII. of the 
 Enquiry, where mathematical para- 
 doxes are used to show the weakness 
 of reason.) 
 
 Sec. 6. ' Of the Ideas of Existence and of External 
 Existence.' 
 
 Part III. 
 
 Sec. I. 'Of Knowledge.' (Represented in the En- 
 quiry only by the distinction between 
 matters of fact and relations of ideas.) 
 " 3. ' Why a Cause is always Necessary.' 
 " 10. ' Of the Influence of Belief.' 
 Sees. II, 12, 13. Probability. (Represented by only 
 
 two pages of the Enquiry.) 
 Sec. 15. 'Rules by which to judge of Causes and 
 Effects.' 
 
 Part IV. 
 
 Sec. 2. Why we believe in external things. 
 
 " 3. ' Of the Ancient Philosophy.' The ideas of 
 Substances, Accidents, and Occult Quali- 
 ties. 
 
 " 5. ' Of the Immateriality of the Soul.' 
 
 " 6. ' Of Personal Identity.' 
 
BRIEF EXPOSITION OF HUMES PHILOSOPHY. 53 
 
 Parts of the ^Enquiry ' not Represented in the ' Treatise.' 
 
 Sec. I. The distinction between the Rhetorical and 
 the Critical Philosophy. 
 
 " 10. ' Of Miracles.' 
 
 "11. ' Of a Particular Providence and of a Future 
 State.' 
 
 " 12. The distinction between Pyrrhonism or ex- 
 cessive scepticism and the Academical 
 Philosophy or a more mitigated scepti- 
 cism. 
 
HUME'S INFLUENCE UPON SUB- 
 SEQUENT PHILOSOPHIC 
 THOUGHT. 
 
 Hume's reasoning, which finds its logical conclusion 
 in total and helpless scepticism, showed how hopeless 
 was the attempt to account for knowledge on Locke's 
 theory that all ideas are derived from sense, and how 
 impossible it was to justify knowledge on Descartes' 
 principle that ideas which cannot be proved to repre- 
 sent reality should be treated as false. It therefore 
 led on the one side to Kant's search for the innate 
 forms of knowledge overlooked by Locke, and on the 
 other to Reid's philosophy of Common Sense which 
 rejected the whole ' ideal system' and held to an im- 
 mediate knowledge of reality. 
 
 Again, by eliminating all necessity from nature and 
 by making all reasoning depend ultimately upon the 
 imagination, Hume threw doubts upon the funda- 
 mental assumptions of Spinoza and the other ration- 
 alistic Ontologists who had been carried away by the 
 mathematical sciences and had tried to make the 
 universe ' a system of abstract truths related to each 
 other as the propositions of Euclid are related to his 
 axioms and substantialized by their reference to 
 God or pure Being.' When he had done this, the 
 Materialists proposed to "escape to the world of tan- 
 gible, visible, sense-giving realities."* Thus Hume 
 
 * Stephen : English Thought in the Eighteenth Century, I., 65. 
 
 55 
 
56 INFLUENCE UPON PHILOSOPHIC THOUGHT. 
 
 gave a new impulse to the French Illumination with 
 its wide-spread influences. 
 
 Hume has also exerted an immense direct influence 
 over the course of English thought. His religious es- 
 says with their clear style, coming as they did at the 
 close of the Deistic Controversy, attracted more im- 
 mediate attention than his philosophical writings ; and 
 they are still the arsenal from which most anti-theo- 
 logical weapons are borrowed. The Treatise was too 
 obscure to be read by the general public, even after at- 
 tention had been called to it through the various En- 
 quiries ; so that as late as 1808 an unfriendly critic felt 
 at liberty to write : " His strictly philosophical works 
 seem likely to fall into utter neglect; but his History, 
 we need not say, is the basis of his permanent reputa- 
 tion. " * Yet in the English Associational School the 
 influence of Hume's psychology has been deeply felt. 
 
 At the present time his importance is fully recog- 
 nized ; and Professor Huxley on the one hand de- 
 scribes him " as the parent of Kant and as the pro- 
 tagonist of that more modern way of thinking which 
 has been called ' agnosticism ' ", and says that " that 
 to which succeeding generations have made, are mak- 
 ing, and will make continual additions is Hume's 
 fame as a philosopher " ; f while on the other hand 
 the late Professor Green called him the " last great 
 English philosopher ", but made use of him to show 
 how hollow this " more modern way of thinking " is J 
 
 * John Foster, in the Eclectic Review. 
 
 \ ' Hume ' — English Men of Letters Series — pp. 58, 43. 
 
 J Introduction to his edition of the Treatise. 
 
THE PHILOSOPHY OF HUME AS CON- 
 TAINED IN EXTRACTS FROM THE 
 FIRST BOOK AND THE FIRST AND 
 SECOND SECTIONS OF THE 
 THIRD PART OF THE 
 SECOND BOOK OF THE 
 TREATISE OF HU- 
 MAN NATURE. 
 
 57 
 
THE PHILOSOPHY OF HUME. 
 
 INTRODUCTION. 
 
 It is evident that all the sciences have a relation, 
 greater or less, to human nature ; and that however 
 wide any of them may seern to run from it, they still 
 return back by one passage or another. Even Mathe- 
 matics, Natural Philosophy, and Natural Religion are 
 in some measure dependent on the science of Man ; 
 since they lie under the cognizance of men, and are 
 judged of by their powers and faculties. It is impossi- 
 ble to tell what changes and improvements we might 
 make in these sciences were we thoroughly acquainted 
 with the extent and force of human understanding, 
 and could explain the nature of the ideas we employ, 
 and of the operations we perform in our reasonings. 
 
 There is no question of importance whose decision 
 is not comprised in the science of man ; and there is 
 none which can be decided with any certainty before 
 we become acquainted with that science. In pretend- 
 ing therefore to explain the principles of human 
 nature, we in effect propose a complete system of the 
 sciences, built on a foundation almost entirely new, 
 and the only one upon which they can stand with any 
 security. And, as the science of man is the only solid 
 
 59 
 
6o INTRODUCTION. 
 
 foundation for the other sciences, so the only solid 
 foundation we can give to this science itself must be 
 laid on experience and observation. 
 
 For to me it seems evident that, the essence of the 
 mind being equally unknown to us with that of exter- 
 nal bodies, it must be equally impossible to form any 
 notion of its powers and qualities otherwise than from 
 careful and exact experiments and the observation of 
 those particular effects which result from its different 
 circumstances and situations. 
 
 We must therefore glean up our experiments in this 
 science from a cautious observation of human life, 
 and take them as they appear in the common course 
 of the world, by men's behavior in company, in affairs, 
 and in their pleasures. Where experiments of this 
 kind are judiciously collected and compared, we may 
 hope to establish on them a science which will not 
 be inferior in certainty, and will be much superior in 
 utility, to any other of human comprehension. 
 
PART I. 
 
 OF IDEAS, THEIR ORIGIN; COMPOSITION, CON- 
 NECTION, ABSTRACTION, ETC. 
 
 SECTION I. 
 
 Of the origin of our ideas. 
 
 All the perceptions of the human mind resolve 
 themselves into two distinct kinds, which I shall call 
 Impressions and Ideas. The difference betwixt 
 these consists in the degrees of force and liveliness 
 with which they strike upon the mind and make their 
 way into our thought or consciousness. Those per- 
 ceptions which enter with most force and violence 
 we may name impressions ; and under this name I 
 comprehend all our sensations, passions, and emotions, 
 as they make their first appearance in the soul. By 
 ideas I mean the faint images of these in thinking and 
 reasoning ; such as, for instance, are all the percep- 
 tions excited by the present discourse, excepting only 
 those which arise from the sight and touch, and ex- 
 cepting the immediate pleasure or uneasiness it may 
 occasion. I believe it will not be very necessary to 
 employ many words in explaining this distinction. 
 
 6i 
 
62 THE PHILOSOPHY OF HOME. [Part I. 
 
 Every one of himself will readily perceive the differ- 
 ence betwixt feeling and thinking. The common de- 
 grees of these are easily distinguished; though it is 
 not impossible but in particular instances they may 
 very nearly approach to -each other. Thus in sleep, 
 in a fever, in madness, or in any very violent emotions 
 of soul, our ideas may approach to our impressions; as 
 on the other hand it sometimes happens that our im- 
 pressions are so faint and low that we cannot dis- 
 tinguish them from our ideas. But notwithstanding 
 this near resemblance in a few instances, they are in 
 general so very different that no one can make a 
 scruple to rank them under distinct heads, and assign 
 to each a peculiar name to mark the difference. 
 
 There is another division of our perceptions which 
 it will be convenient to observe, and which extends 
 itself both to our impressions and ideas. This divi- 
 sion is into Simple and Complex. Simple percep- 
 tions or impressions and ideas are such as admit of 
 no distinction nor separation. The complex are the 
 contrary to these, and may be distinguished into parts. 
 Though a particular color, taste, and smell are quali- 
 ties all united together in this apple, it is easy to per- 
 ceive they are not the same, but are at least distin- 
 guishable from each other. 
 
 Though there is in general a great resemblance 
 betwixt our complex impressions and ideas, yet the 
 rule is not universally true that they are exact copies 
 of each other; for I can imagine to myself such a 
 city as the Neiv Jerusalem, whose ])avement is gold 
 and walls are rubies, though I never saw any such. 
 AVe may next consider how the case stands with our 
 
Sec. I.] OF IDEAS. 63 
 
 simple perceptions. After the most accurate exam- 
 ination of which I am capable, I venture to affirm 
 that the rule here holds without any exception, and 
 that every simple idea has a simple impression, which 
 resembles it ; and every simple impression a corre- 
 spondent idea. That idea of red which we form in 
 the dark, and that impression which strikes our eyes 
 in sunshine, differ only in degree, not in nature. 
 
 We shall here content ourselves with establishing 
 one general proposition. Thai all our simple ideas in 
 their first appearance are derived from simple impres- 
 sions, which are correspondent to them, and which they 
 exactly represent. AVe find that any impression either 
 of the mind or body is constantly followed by an 
 idea which resembles it and is only different in the 
 degrees of force and liveliness. The constant con- 
 junction of our resembling perceptions is a convincing 
 proof that the one are the causes of the other ; and 
 this priority of the impressions is an equal proof that 
 our impressions are tlie_causes of our ideas, not our 
 ideas of our impressions. 
 
 As our ideas are images of our impressions, so we 
 can form secondary ideas, which are images of the 
 primary; but, as the first ideas are supposed to be de- 
 rived from impressions, it still remains true that all 
 our simple ideas proceed either mediately or imme- 
 diately from their correspondent impressions. 
 
 This then is the first principle I establish in the 
 science of human nature. 
 
64 THE PHILOSOPHY OF HUME. [PART I. 
 
 SECTIONS II., III. 
 
 Division of the subject, and of the ideas of memory 
 and imagination. 
 
 Impressions may be divided into two kinds, those 
 of Sensation and those of Reflection. The first 
 kind arises in the soul originally, from unknown 
 causes. The second is derived in a great measure 
 from our ideas, and that in the following order. An 
 impression first strikes upon the senses, and makes us 
 perceive heat or cold, thirst or hunger, pleasure or 
 pain of some kind or other. Of this impression there 
 is a copy taken by the mind, which remains after the 
 impression ceases ; and this we call an idea. This 
 idea of pleasure or pain, when it returns upon the soul 
 produces the new impressions of desire and aversion, 
 hope and fear, which may properly be called impres- 
 sions of reflection, because derived from it. These 
 again are copied by the memory and imagination, and 
 become ideas ; which perhaps in their turn give rise 
 to other impressions and ideas. So that the impres- 
 sions of reflection are only antecedent to their corre- 
 spondent ideas ; but posterior to those of sensation, 
 and derived from them. 
 
 We find by experience that when any impression 
 has been present with the mind it again makes its 
 appearance there as an idea ; and this it may do after 
 two different ways : either when in its new appearance 
 it retains a considerable degree of its first vivacity 
 and is somewhat intermediate betwixt an impression 
 
Sec. IV.] OF IDEAS. 65 
 
 and an idea ; or when it entirely loses that vivacity, 
 and is a perfect idea. The faculty by which we repeat 
 our impressions in the first manner is called the 
 Memory, and the other the Imagination. It is 
 evident at first sight that the ideas of the mem- 
 ory are much more lively and strong than those of the 
 imagination, and that the former faculty paints its 
 objects in more distinct colors than any vifhich are 
 employed by the latter. When we remember any past 
 event, the idea of it flows in upon the mind in a for- 
 cible manner ; whereas in the imagination the percep- 
 tion is faint and languid, and cannot without difficulty 
 be preserved by the mind steady and uniform for any 
 considerable time. Here then is a sensible difference 
 betwixt one species of ideas and another. But of this 
 more fully hereafter. 
 
 There is another difference betwixt these two kinds 
 of ideas which is no less evident, namely, that though 
 neither the ideas of the memory nor imagination, 
 neither the lively nor faint ideas, can make their ap- 
 pearance in the mind unless their correspondent im- 
 pressions have gone before to prepare the way for 
 them, yet the imagination is not restrained to the 
 same order and form with the original impressions; 
 while the memory is in a manner tied down in that 
 respect, without any power of variation. 
 
 SECTION IV. 
 
 Of the connection or association of ideas. 
 
 As all simple ideas may be separated by the imagi- 
 nation, and may be united again in what form it 
 
66 THE PHILOSOPHY OF HUME. [PART I. 
 
 pleases, nothing would be more unaccountable than 
 the operations of that faculty, were it not guided by 
 some universal principles, which render it in some 
 measure uniform with itself in all times and places. 
 Were ideas entirely loose and unconnected, chance 
 alone would join them; and it is impossible the same 
 simple ideas should fall regularly into complex ones 
 (as they commonly do) without some bond of union 
 among them, some associating quality, by which one 
 idea naturally introduces another. The qualities 
 from which this association arises, and by which the 
 mind is after this manner conveyed from one idea to 
 another, are three, viz., Resemblance, Contiguity in 
 time or place, and Cause and Effect. 
 
 It is plain that in the course of our thinking, and 
 in the constant revoluiion of our ideas, our imagina- 
 tion runs easily from one idea to any other that resent- 
 bles it, and that this quality alone is to the fancy a 
 sufficient bond and association. It is likewise evi- 
 dent that as the senses, in changing their objects, are 
 necessitated to change them regularly, and take them 
 as they lie contiguous to each other, the imagination 
 must by long custom acquire the same method of 
 thinking, and run along the parts of space and time in 
 conceiving its objects. As to the connection that 
 is made by the relation of cause and effect, we shall 
 have occasion afterwards to examine it to the bottom, 
 and therefore shall not at present insist upon it. It is 
 sufficient to observe that there is no relation which 
 produces a stronger connection in the fancy, and 
 makes one idea more readily recall another, than the 
 relation of cause and effect betwixt their objects. 
 
Sec. V.l OF IDEAS. 67 
 
 That we may understand the full extent of these re- 
 lations we must consider that two objects are con- 
 nected together in the imagination, not only when the 
 one is immediately resembling, contiguous to, or the 
 cause of the other, but also when there is interposed 
 betwixt them a third object which bears to both of 
 them any of these relations. This may be carried on 
 to a great length; though at the same time we may 
 observe that each remove considerably weakens the 
 relation. 
 
 Amongst the effects of this union or association of 
 ideas, there are none more remarkable than those 
 complex ideas which are the common subjects of our 
 thoughts and reasoning and generally arise from some 
 principle of union among our simple ideas. These 
 complex ideas may be divided into Relations, Modes, 
 and Substances. We shall briefly examine each of 
 these in order, and shall subjoin some considerations 
 concerning our general and particular ideas, before we 
 leave the present subject, which may be considered 
 as the elements of this philosophy. 
 
 SECTION V. 
 
 Of relations. 
 
 The word Relation is commonly used in two senses 
 considerably different from each other. Either for 
 that quality by which two ideas are connected to- 
 gether in the imagination and the one naturally intro- 
 duces the other, after the manner above explained ; or 
 for that particular circumstance in which, even upon 
 the .^rbitrarjr union of two ideas in the fancy, we may 
 
68 THE PHILOSOPHY OF HUME. [PART I. 
 
 think proper to compare them. In common language 
 the former is always the sense in which we use the 
 word relation; and it is only in philosophy that we 
 extend it to mean any particular subject of compari- 
 son, without a connecting principle. Thus distance 
 will be allowed by philosophers to be a true relation, 
 because we acquire an idea of it by the comparing of 
 objects ; but in a common way we say that nothing 
 can be more distant than such or such things from each 
 other, nothing can have less relation, as if distance and 
 relation were incompatible. 
 
 It may perhaps be esteemed an endless task to enu- 
 merate all those qualities which make objects admit 
 of comparison, and by which the ideas oi philosophical 
 relation are produced. But if we diligently consider 
 them we shall find that without difficulty they may be 
 comprised under seven general heads, which may be 
 considered as the sources of d\\ philosophical relation. 
 
 1. The first is resemblance : and this is a relation 
 without which no philosophical relation can exist ; 
 since no objects will admit of comparison but what 
 have some degree of resemblance. But, though resem- 
 blance be necessary to all philosophical relation, it 
 does not follow that it always produces a connection 
 or association of ideas. When a quality becomes very 
 general and is common to a great many individuals, 
 it leads not the mind directly to any one of them ; 
 but, by presenting at once too great a choice, does 
 thereby prevent the imagination from fixing on any 
 single object. 
 
 2. Identity may be esteemed a second species of 
 relation. This relation I here consider as applied in 
 
Sec. v.] of ideas. 69 
 
 its strictest sense to constant and unchangeable ob- 
 jects ; without examining the nature and foundation 
 of personal identity, which shall find its place after- 
 wards. Of all relations the most universal is that of 
 identity, being common to every being whose exist- 
 ence has any duration. 
 
 3. After identity the most universal and compre- 
 hensive relations are those of Space and Time, which 
 are the sources of an infinite number of comparisons, 
 such as distant, contiguous, above, below, before, after, &c. 
 
 4. All those objects which admit of quantity or 
 ninnber may be compared in that particular ; which 
 is another very fertile source of relation. 
 
 5. When any two objects possess the same quality 
 in common, the degrees in which they possess it 
 form a fifth species of relation. Thus, of two objects 
 which are both heavy, the one may be either of 
 greater or less weight than the other. Two colors 
 that are of the same kind may yet be of different 
 shades, and in that respect admit of comparison. 
 
 6. The relation of contrariety may at first sight be 
 regarded as an exception to the rule that no relation 
 of any kind cati subsist without some degree of resem- 
 blance. But let us consider that no two ideas are in 
 themselves contrary except those of existence and 
 non-existence, which are plainly resembling, as imply- 
 ing both of them an idea of the object ; though the 
 latter excludes the object from all times and places 
 in which it is supposed not to exist. 
 
 7. All other objects, such as fire and water, heat 
 and cold, are only found to be contrary from experi- 
 ence, and from the contrariety of their causes or effects ; 
 
70 THE PHILOSOPHY OF HUME. [PARI I. 
 
 which relation of cause and effect is a seventh philo- 
 sophical relation, as well as a natural one. The re- 
 semblance implied in this relation shall be explained 
 afterwards. 
 
 It might naturally be expected that I should join 
 difference to the other relations. But that I consider 
 rather as a negation of relation than as anything real 
 or positive. Difference is of two kinds as opposed 
 either to identity or resemblance. The first is called 
 a difference of nu7nber ; the other of kind. 
 
 SECTION VI. 
 Of modes and substances. 
 
 I WOULD fain ask those philosophers who found so 
 much of their reasonings on the distinction of sub- 
 stance and accident, and imagine we have clear ideas 
 of each, whether the idea of substance be derived from 
 the impressions of sensation or of reflection ? If it be 
 conveyed to us by our senses, I ask, which of them ; 
 and after what manner ? If it be perceived by the 
 eyes, it must be a color ; if by the ears, a sound ; if 
 by the palate, a taste ; and so of the other senses. 
 But I believe none will assert that substance is either 
 a color, or sound, or a taste. The idea of substance 
 must therefore be derived from an impression of re- 
 flection, if it really exist. But the impressions of re- 
 flection resolve themselves into our passions and emo- 
 tions ; none of which can possibly represent a sub- 
 stance. We have therefore no idea of substance, dis- 
 tinct from that of a collection of particular qualities, 
 
Sec. VI.] OE IDEAS. 'ji 
 
 nor have we any other meaning when we either talk 
 or reason concerning it. 
 
 The idea of a substance, as well as that of a mode, 
 is nothing but a collection of simple ideas that are 
 united by the imagination and have a particular 
 name assigned them, by which we are able to recall, 
 either to ourselves or others, that collection. But 
 the difference betwixt tliese ideas consists in this, 
 that the particular qualities which form a substance 
 are commonly referred to an unknown something in 
 which they are supposed to inhere ; or, granting this 
 fiction should not take place, are at least supposed to 
 be closely and inseparably connected by the relations 
 of contiguity and causation. The effect of this is 
 that whatever new simple quality we discover to have 
 the same connection with the rest, we immediately 
 comprehend it among them, even though it did not 
 enter into the first conception of the substance. 
 Thus our idea of gold may at first be a yellow color, 
 weight, malleableness, fusibility ; but upon the dis- 
 covery of its dissolubility in aqua regia, we join that to 
 the qualities, and suppose it to belong to the substance 
 as much as if its idea had from the beginning made a 
 part of the compound one. The principle of union 
 being regarded as the chief part of the complex idea 
 gives entrance to whatever quality afterwards occurs, 
 and is equally comprehended by it as are the others, 
 which first presented themselves. 
 
 That this cannot take place in modes is evident 
 from considering their nature. The simple ideas of 
 which modes are formed either represent qualities 
 which are not united by contiguity and causation, 
 
72 THE PHILOSOPHY OF HUME. [PART I. 
 
 but are dispersed in different subjects ; or if they be 
 all united together, the uniting principle is not re- 
 garded as the foundation of the complex idea. The 
 idea of a dance is an instance of the first kind of 
 modes ; that of beauty of the second. The reason is 
 obvious why such complex ideas cannot receive any 
 new idea without changing the name which distin- 
 tinguishes the mode. 
 
 SECTION VII. 
 
 Of abstract ideas. 
 
 A VERY material question has been started concern- 
 ing abstract or general ideas, whether they be general or 
 particular in the tnind's conception of them. A * great 
 philosopher has disputed the received opinion in this 
 particular, and has asserted that all general ideas are 
 nothing but particular ones annexed to a certain 
 term which gives them a more extensive signification 
 and makes them recall upon occasion other individu- 
 als which are similar to them. As I look upon this 
 to be one of the greatest and most valuable discover- 
 ies that has been made of late years in the republic of 
 letters, I shall here endeavor to confirm it by some 
 arguments which I hope will put it beyond all doubt 
 and controversy. 
 
 It is evident that in forming most of our general 
 ideas, if not all of them, we abstract from every par- 
 ticular degree of quantity and quality, and that an 
 object ceases not to be of any particular species on 
 account of every small alteration in its extension, 
 * Dr. Berkeley. 
 
Sec. VII.] OF IDEAS. 73 
 
 duration, and other properties. It may therefore be 
 thought that here is a plain dilemma that decides 
 concerning the nature of those abstract ideas which 
 have afforded so much speculation to philosophers. 
 The abstract idea of a man represents men of all 
 sizes and all qualities ; which it is concluded it can- 
 not do, but either by representing at once all possible 
 sizes and all possible qualities, or by representing no 
 particular one at all. Now, it having been esteemed 
 absurd to defend the former proposition, as implying 
 an infinite capacity in the mind, it has been com- 
 monly inferred in favor of the latter ; and our abstract 
 ideas have been supposed to represent no particular 
 degree either of quantity or quality. But that this 
 inference is erroneous I shall endeavor to make ap- 
 pear, yfrx/, by proving that it is utterly impossible to 
 conceive any quantity or quality without forming a 
 precise notion of its degrees ; and, secondly, by show- 
 ing that, though the capacity of the mind be not in- 
 finite, yet we can at once form a notion of all possible 
 degrees of quantity and quality, in such a manner, at 
 least, as, however imperfect, may serve all the purposes 
 of reflection and conversation. 
 
 To begin with the first proposition, that the mind 
 cannot form any notion of quantity or quality ivithout 
 forming a precise notion of degrees of each j we may 
 prove this by the three following arguments. First, 
 we have observed that whatever objects are different 
 are distinguishable, and that whatever objects are dis- 
 tinguishable are separable by the thought and imagi- 
 nation. And we may here add that these proposi- 
 tions are equally true in the inverse, and that whatever 
 
74 THE PHILOSOPHY OF HUME. [Part I. 
 
 objects are separable are also distinguishable, and 
 that whatever objects are distinguishable are also dif- 
 ferent. For how is it possible we can separate what 
 is not distinguishable, or distinguish what is not dif- 
 ferent ? In order therefore to know whether abstrac- 
 tion implies a separation, we need only consider it in 
 this view, and examine whether all the circumstances 
 which we abstract from in our general ideas be such 
 as are distinguishable and different from those which 
 we retain as essential parts of them. But it is evident 
 at first sight that the precise length of a line is not 
 different nor distinguishable from the line itself ; nor 
 the precise degree of any quality from the quality. 
 These ideas, therefore, admit no more of separation 
 than they do of distinction and difference. They are 
 consequently conjoined with each other in the con- 
 ception ; and the general idea of a line, notwithstand- 
 ing all our abstractions and refinements, has in its 
 appearance in the mind a precise degree of quantity 
 and quality ; however it may be made to represent 
 others which have different degrees of both. 
 
 Secondly, it is confessed that no object can appear to 
 the senses, or, in other words, that no impression can 
 become present to the mind, without being determined 
 in its degrees of both quantity and quality. 
 
 Now, since all ideas are derived from impressions, 
 and are nothing but copies and representations of 
 them, whatever is true of the one must be acknowl- 
 edged concerning the other. Impressions and ideas 
 differ only in their strength and vivacity. 
 
 Thirdly, it is a principle generally received in phi- 
 losophy, that everything in nature is individual, and 
 
Sec. VII.] OF IDEAS. 75 
 
 that it is utterly absurd to suppose a triangle really 
 existent which has no precise proportion of sides 
 and angles. If this therefore be absurd in fact and 
 reality, it must also be absurd in idea ; since nothing 
 of which we can form a clear and distinct idea is 
 absurd and impossible. Abstract ideas are therefore 
 in themselves individual, however they may become 
 general in their representation. The image in the 
 mind is only that of a particular object, though the 
 application of it in our reasoning be the same as if it 
 were universal. 
 
 This application of ideas beyond their nature pro- 
 ceeds from our collecting all their possible degrees of 
 quantity and quality in such an imperfect manner as 
 may serve the purposes of life, which is the second 
 proposition I proposed to explain. When we have 
 found a resemblance among several objects that often 
 occur to us, we apply the same name to all of them, 
 whatever differences we may observe in the degrees 
 of their quantity and quality, and whatever other dif- 
 ferences may appear among them. After we have ac- 
 quired a custom of this kind, the hearing of that name 
 revives the idea of one of these objects, and makes the 
 imagination conceive it with all its particular circum- 
 stances and proportions. 
 
 After the mind has produced an individual idea, 
 upon which we reason, the attendant custom revived 
 by the general or abstract term readily suggests any 
 other individual, if by chance we form any reasoning 
 that agrees not with it. Thus should we mention the 
 word, triangle, and form the idea of a particular equi- 
 lateral one to correspond to it, and should we after- 
 
76 THE PHILOSOPHY OF HUME. [PART I. 
 
 wards assert that the three angles of a triangle are equal 
 to each other, the other individuals of a scalenum and 
 isosceles, which we overlooked at first, immediately 
 crowd in upon us, and make us perceive the false- 
 hood of this proposition, though it be true with relation 
 to that idea which we had formed. If the mind sug- 
 gests not always these ideas upon occasion, it pro- 
 ceeds from some imperfection in its faculties ; and 
 such a one as is often the source of false reasoning 
 and sophistry. But this is principally the case with 
 those ideas which are abstruse and compounded. On 
 other occasions the custom is more entire, and it is 
 seldom we run into such errors. 
 
 Before I leave this subject I shall employ the same 
 principles to explain that distinction of reason which 
 is so much talked of, and is so little understood, in 
 the schools. Of this kind is the distinction betwixt 
 figure and the body figured, motion and the body 
 moved. The difficulty of explaining this distinction 
 arises from the principle above explained, that all 
 ideas which are different are separable. For it follows 
 from thence that, if the figure be different from the 
 body, their ideas must be separable as well as dis- 
 tinguishable ; if they be not different, their ideas can 
 neither be separable nor distinguishable. What then 
 is meant by a distinction of reason, since it implies 
 neither a difference nor separation ? 
 
 To remove this difficulty we must have recourse to 
 the foregoing explication of abstract ideas. It is 
 certain that the mind would never have dreamed of 
 distinguishing a figure from the body figured, as being 
 in reality neither distinguishable, nor different, nor 
 
Sec. VII.] OF IDEAS. 77 
 
 separable, did it not observe that even in this 
 simplicity there might be contained many different 
 resemblances and relations. Thus, when a globe of 
 white marble is presented, we receive only the im- 
 pression of a white color disposed in a certain form, 
 nor are we able to separate and distinguish the color 
 from the form. But, observing afterwards a globe of 
 black marble and a cube of white, and comparing 
 them with our former object, we find two separate 
 resemblances in what formerly seemed, and really is, 
 perfectly inseparable. After a little more practice of 
 this kind we begin to distinguish the figure from the 
 color by a distinction of reason; that is, we consider 
 the figure and color together, since they are in effect 
 the same and undistinguishable ; but still view them 
 in different aspects, according to the resemblances of 
 which they are susceptible. When we would consider 
 only the figure of the globe of white marble, we form 
 in reality an idea both of the figure and color, but 
 tacitly carry our eye to its resemblance with the globe 
 of black marble : and in the same manner, when we 
 would consider its color only, we turn our view to its 
 resemblance with the cube of white marble. By this 
 means we accompany our ideas with a kind of reflec- 
 tion, of which custom renders us in a great measure 
 insensible. A person who desires us to consider the 
 figure of a globe of white marble without thinking on 
 its color desires an impossibility ; but his meaning is 
 that we should consider the color and figure together, 
 but still keep in our eye the resemblance to the globe 
 of black marble, or that to any other globe of what- 
 ever color or substance. 
 
PART IL 
 
 OF THE IDEAS OF SPACE AND TIME. 
 
 SECTIONS I., II. 
 
 Of the infinite divisibility of space and time. 
 
 It is universally allowed that the capacity of 
 the mind is limited and can never attain a full and 
 adequate conception of infinity. It is also obvious 
 that whatever is capable of being divided iti in- 
 finitum must consist of an infinite number of parts, 
 and that it is impossible to set any bounds to 
 the number of parts without setting bounds at the 
 same time to the division. It requires scarce any 
 induction to conclude from lience that the idea 
 which we form of any finite quality is not infinitely 
 divisible, but that by proper distinctions and separa- 
 tions we may run up this idea to inferior ones which 
 will be perfectly simple and indivisible. In rejecting 
 the infinite capacity of the mind we suppose it may 
 arrive at an end in the division of its ideas ; nor are 
 there any possible means of e\ading the evidence of 
 this conclusion. 
 
 It is therefore certain that the imagination reaches 
 
 78 
 
SecS. I, II.] OF SPACE AND TIME. 79 
 
 a i/niiiiiium, and may raise up to itself an idea of 
 which it cannot conceive any sulj-divibion, and whicli 
 cannot be diminisl^ed without a total anniliilation. 
 When you tell me of the thousandth and ten thou- 
 sandth part of a grain of sand, I have a distinct idea 
 of these numbers and of their different proportions ; 
 l)Ut the images which I form in my mind to represent 
 the things themselves are nothing different from each 
 other, nor inferior to that image by which I represent 
 the grain of sand itself which is supposed so vastly to 
 exceed them. 
 
 It is an established maxim in metaphysics That 
 whatever the mind clearly conceives includes the idea of 
 possible existence, or, in other words, that nothing we 
 imagine is absolutely impossible. AVe can form tlie idea 
 of a golden mountain, and from thence conclude that 
 such a mountain may actually exist. We can form no 
 idea of a mountain without a valley, and therefore 
 regard it as impossible. 
 
 Now it is certain we have an idea of extension ; 
 for otherwise why do we talk and reason concerning 
 it ? It is likewise certain that this idea as conceived 
 by the imagination, though divisible into parts or 
 inferior ideas, is not infinitely divisible, nor consists 
 of an infinite number of parts : for that exceeds the 
 comprehension of our limited capacities. Here then 
 is an idea of extension which consists of parts or 
 inferior ideas that are perfectly indivisible : conse- 
 quently this idea implies no contradiction : conse- 
 quently it is possible for extension really to exist con- 
 formable to it : and consequently all the arguments 
 employed against the possibility of mathematical 
 
So THE PHILOSOPHY OF HUME. [PART II. 
 
 points are mere scholastic quibbles and unworthy 
 of our attention. 
 
 These consequences we may carry one step farther 
 and conclude that all the pretended demonstrations 
 for the infinite divisibility of extension are equally 
 sophistical ; since it is certain these demonstrations 
 cannot be just without proving the impossibility of 
 mathematical points ; which it is an evident absurdity 
 to pretend to. 
 
 All this reasoning takes place with regard to time. 
 
 SECTIONS III., IV. 
 Of the other qualities of our ideas of space and time. 
 
 No discovery could have been made more happily 
 for deciding all controversies concerning ideas than 
 that above mentioned, that impressions always take 
 the precedency of them and that every idea with 
 which the imagination is furnished first makes its ap- 
 pearance in a correspondent impression. These 
 latter perceptions are all so clear and evident that 
 they admit of no controversy ; though many of our 
 ideas are so obscure that it is almost impossible even 
 for the mind which forms them to tell exactly their 
 nature and composition. Let us apply this principle 
 in order to discover farther the nature of our ideas of 
 space and time. 
 
 The idea of space is conveyed to the mind by two 
 senses, the sight and touch ; nor does anything ever 
 appear extended tliat is not either visible or tangible. 
 That compound impression which represents exten- 
 
Secs. Ill, IV.] OF SPACE AND TIME. 8l 
 
 sion consists of several lesser impressions, that are 
 indivisible to the eye or feeling and may be called 
 impressions of atoms or corpuscles, endowed with 
 color and solidity. But this is not all. It is not 
 only requisite that these atoms should be colored 
 or tangible in order to discover themselves to our 
 senses ; it is also necessary we should preserve the 
 idea of their color or tangibility in order to compre- 
 hend them by our imagination. There is nothing but 
 the idea of their color or tangibility which can render 
 them conceivable by the mind. Upon the removal 
 of the ideas of these sensible qualities they are ut- 
 terly annihilated to the thought or imagination. 
 
 As it is from the disposition of visible and tangible 
 objects we receive the idea of space, so from the suc- 
 cession of ideas and impressions we form the idea of 
 time ; nor is it possible for time alone ever to make 
 its appearance or be taken notice of by the mind. A 
 man in a sound sleep, or strongly occupied with one 
 thought, is insensible of time ; and according as his 
 perceptions succeed each other with greater or less 
 rapidity the same duration appears longer or shorter 
 to his imagination. Wherever we have no successive 
 perceptions we have no notion of time, even though 
 there be a real succession in the objects. From 
 these phenomena, as well as from many others, we 
 may conclude that time cannot make its appearance 
 to the mind either alone or attended with a steady, 
 unchangeable object, but is always discovered by 
 some perceivable succession of changeable objects. 
 
 In order to know whetlier any objects which are 
 joined in impression be separable in idea, we need 
 
82 THE PHILOSOPHY OF HUME. [PART II 
 
 only consider if they be different from each other ; in 
 which case it is plain they may be conceived apart. 
 The idea of time is not derived from a particular im- 
 pression mixed up with others and plainly distinguish- 
 able from them, but arises altogether from the manner 
 in which impressions appear to the mind, without mak- 
 ing one of the number. Five notes played on a flute 
 give us the impression and idea of time, though time 
 be not a sixth impression which presents itself to the 
 hearing or any other of the senses. Nor is it a sixth 
 impression which the mind by reflection finds in 
 itself. 
 
 The ideas of space and time are therefore no sep- 
 arate or distinct ideas, but merely those of the man- 
 ner or order in which objects exist. Or, in other 
 words, it is impossible to conceive either a vacuum, 
 and extension without matter, or a time when there 
 was no succession or change in any real existence. 
 
 I know there are some who pretend that the idea 
 of duration is applicable in a proper sense to objects 
 which are perfectly unchangeable ; and this I take to 
 be the common opinion of philosophers as well as of 
 the vulgar. But, though it be impossible to show the 
 impression from which the idea of time without a 
 changeable existence is derived, yet we can easily 
 point out those appearances which make us fancy we 
 have that idea. For we may observe that there is a 
 continual succession of perceptions in our mind ; so 
 that, the idea of time being forever present with us, 
 when we consider a steadfast object at five o'clock 
 and regard the same at six, we are apt to apply to it 
 that idea in the same manner as if every moment 
 
Sec. VI.] OF SPACE AND TIME. 83 
 
 were distinguished by a different position or an altera- 
 tion of the object. The first and second appearances 
 of the object, being compared with the succession of 
 our perceptions, seem equally removed as if the ob- 
 ject had really changed. To which we may add, 
 what experience shows us, that the object was sus- 
 ceptible of such a number of changes betwixt these 
 appearances ; as also that the unchangeable or rather 
 fictitious duration has the same effect upon every 
 quality, by increasing or diminishing it, as that suc- 
 cession which is obvious to the senses. From these 
 three relations we are apt to confound our ideas, and 
 imagine we can form the idea of a time and duration 
 without any change or succession. 
 
 SECTION VI. 
 
 Of the idea of existence, and of external existence. 
 
 Since we never remember any idea or impression 
 without attributing existence to it, the idea of exist- 
 ence must either be derived from a distinct impres- 
 sion, conjoined with every perception or object of our 
 thought, or must be the very same with the idea 
 of the perception or object. 
 . As this dilemma is an evident consequence of the 
 principle that every idea arises from a similar impres- 
 sion, so our decision betwixt the propositions of the 
 dilemma is no more doubtful. So far from there 
 being any distinct impression attending every impres- 
 sion and every idea, that I do not think there are any 
 two distinct impressions which are inseparably con- 
 
84 THE PHILOSOPHY OF HUME. [PART II. 
 
 joined. Though certain sensations may at one time be 
 united, we quickly find they admit of a separation, 
 and may be presented apart. And thus, though every 
 impression and idea we remember be considered as 
 existent, the idea of existence is not derived from any 
 particular impression. 
 
 The idea of existence, then, is the very same with 
 the idea of what we conceive to be existent. To 
 reflect on anything simply, and to reflect on it as ex- 
 istent, are nothing different from each other. That 
 idea when conjoined with the idea of any object 
 makes no addition to it. Whatever we conceive, we 
 conceive to be existent. Any idea we please to form 
 is the idea of a being ; and the idea of a being is any 
 idea we please to form. 
 
 Whoever opposes this must necessarily point out 
 that distinct impression from which the idea of entity 
 is derived, and must prove that this impression is in- 
 separable from every perception we believe to be 
 existent. This we may without hesitation conclude to 
 be impossible. A like reasoning will account for the 
 idea of external existence. 
 
 Since nothing is ever present to the mind but per- 
 ceptions, and since all ideas are derived from something 
 antecedently present to the mind, it follows that it is 
 impossible for us so much as to conceive or form an 
 idea of anything specifically different from ideas and 
 impressions. Let us fix our attention out of our- 
 selves as much as possible ; let us chase our imagina- 
 tion to the heavens, or to the utmost limits of the 
 universe : we never really .advance a step beyond our- 
 selves, nor can conceive any kind of existence but 
 
Sec. VI.] OF SPACE AND TIME. 85 
 
 those perceptions which have appeared in that nar- 
 row compass. This is the universe of the imagina- 
 tion, nor have we any idea but what is there pro- 
 duced. 
 
 The farthest we can go towards a conception of ex- 
 ternal objects, when supposed specifically different 
 from our perceptions, is to form a relative idea of 
 them, without pretending to comprehend the related 
 objects. Generally speaking, we do not suppose 
 them specifically different, but only attribute to them 
 different relations, connections, and durations. But 
 of this more fully hereafter.* 
 
 * Part IV., sec. 11. 
 
PART III. 
 
 OF KNOWLEDGE AND PROBABILITY. 
 
 SECTIONS I., II. 
 
 Of knowledge and probability and the idea of cause and 
 effect. 
 
 There are *seven different kinds of philosophical 
 relation, viz., resemblance, identity, relations of time and 
 place, proportion in quantity or number, degrees in any 
 quality, contrariety, and causation. These relations 
 may be divided into two classes : into such as depend 
 entirely on the ideas which we compare together, 
 and such as may be changed without any change 
 in the ideas. It is from the idea of a triangle that 
 we discover the relation of equality which its three 
 angles bear to two right ones ; and this relation is in- 
 variable, as long as our idea remains the same. On 
 the contrary, the relations of contiguity and distance be- 
 twixt two objects may be changed merely by an altera- 
 tion of their place, without any change on the objects 
 themselves or on their ideas ; and the place depends 
 
 * Part I., sec. \ . 
 
 86 
 
SliCS. I, II.] OF KNOWLEDGE AND PROBABILITY. 87 
 
 on a hundred different accidents which cannot be 
 foreseen by the mind. It is the same case with 
 identity and causation. Two objects, though perfectly 
 resembling each other, and even appearing in the same 
 place at different times, may be numerically different : 
 and as the power by which one object produces 
 another is never discoverable merely from their idea, 
 it is evident cause and effect are relations of which we 
 receive information from experience and not from any 
 abstract reasoning or reflection. There is no single 
 phaenomenon, even the most simple, which can be ac- 
 counted for from the qualities of the objects as they 
 appear to us, or which we could foresee without the 
 help of our memory and experience. 
 
 It appears, therefore, that of these seven philo- 
 sophical relations there remain only four which, de- 
 pending solely upon ideas, can be the objects of 
 knowledge and certainty. These four 3xq resemblance, 
 contrariety, degrees in quality, and proportions in quantity 
 or number. But as to the other three, which depend 
 not upon the idea and may be absent or present even 
 while that remains the same, it will be proper to explain 
 them more particularly. These three relations are 
 identity, the situations in time and place, and causation. 
 
 Of those three relations which depend not upon the 
 mere ideas the only one that can be traced beyond 
 our senses, and informs us of existences and objects 
 which we do not see or feel, is causation. This rela- 
 tion, therefore, we shall endeavor to explain fully be- 
 fore we leave the subject of the understanding. 
 
 To begin regularly, we must consider the idea of 
 causation, and see from what origin it is derived. It is 
 
88 THE PHILOSOPHY OF HUME. [Part III. 
 
 impossible to reason justly without understanding per- 
 fectly the idea concerning which we reason ; and it is 
 impossible perfectly to understand any idea without 
 tracing it up to its origin and examining that primary 
 impression from which it arises. The examination of 
 the impression bestows a clearness on the idea ; and 
 the examination of the idea bestows a like clearness 
 on all our reasoning. 
 
 Let us therefore cast our eye on any two objects 
 which we call cause and effect, and turn them on 
 all sides, in order to find that impression which pro- 
 duces an idea of such prodigious consequence. At 
 first sight I perceive that 1 must not search for it in 
 any of the particular qualities of the objects ; since, 
 whichever of these qualities I pitch on, I find some 
 object that is not possessed of it and yet falls under 
 the denomination of cause or effect. 
 
 The idea, then, of causation must be derived from 
 some relation among objects ; and that relation we 
 must now endeavor to discover. I find, in the first 
 place, that whatever objects are considered as causes 
 or effects are contiguous ; and that nothing can operate 
 in a time or place which is ever so little removed from 
 those of its existence. 
 
 The second relation I shall observe as essential to 
 causes and effects is not so universally acknowledged, 
 but is liable to some controversy. It is that of 
 prioi-ity of time in the cause before the effect. 
 
 Having thus discovered or supposed the two rela- 
 tions of CONTIGUITY and succession to be essential to 
 causes and effects, I find I am stopped short, and can 
 proceed no farther in considering any single instance 
 
SecS. 1, II.] OF KNOWLEDGE AND PROBABILITY. 89 
 
 of cause and effect. Motion in one body is regarded 
 upon impulse as the cause of motion in another. 
 When we consider these objects with the utmost at- 
 tention we find only that the one body approaches 
 the other ; and that the motion of it precedes that of 
 the other, but without any sensible interval. It is in 
 vain to rack ourselves with farther thought and reflec- 
 tion upon this subject. We can go no farther in con- 
 sidering this particular instance. 
 
 Should any one leave this instance and pretend to 
 define a cause by saying it is something productive of 
 another, it is evident he would say nothing. For what 
 does he mean by production 1 Can he give any defi- 
 nition of it that will not be the same with tliat of 
 causation ? If he can ; I desire it may be produced. 
 If he cannot ; he here runs in a circle and gives a 
 synonymous term instead of a definition. 
 
 Shall we then rest contented with these two relations 
 of contiguity and succession, as affording a complete 
 idea of causation ? By no means. An object may be 
 contiguous and prior to another without being con- 
 sidered as its cause. There is a necessary connection 
 to be taken into consideration ; and that relation is of 
 much greater importance than any of the other two 
 above mentioned. 
 
 Here again I turn the object on all sides, in order 
 to discover the nature of this necessary connection, 
 and find the impression, or impressions, from which its 
 idea may be derived. When I cast my eye on the 
 known qualities of objects, I immediately discover that 
 the relation of cause and effect depends not in the 
 least on them. When I consider their relations, I can 
 
go THE PHILOSOPHY OF HUME. [Part 111. 
 
 find none but those of contiguity and succession, 
 which I have already regarded as imperfect and un- 
 satisfactory. Shall the despair of success make me 
 assert that I am here possessed of an idea which is 
 not preceded by any similar impression ? This 
 would be too strong a proof of levity and inconstancy, 
 since the contrary principle has been already so firmly 
 established as to admit of no farther doubt, at least 
 till we have more fully examined the present difficulty. 
 
 We must, therefore, proceed like those who, being 
 in search of anything that lies concealed from them, 
 and not finding it in the place they expected, beat 
 about all the neighboring fields, without any certain 
 view or design, in hopes their good fortune will at 
 last guide them to what they search for. It is neces- 
 sary for us to leave the direct survey of this question 
 concerning the nature of that necessary connection 
 which enters into our idea of cause and effect, and 
 endeavor to find some other questions the examina- 
 tion of which will perhaps afford a hint that may serve 
 to clear up the present difficulty. Of these questions 
 there occur two, which I shall proceed to examine, 
 viz. : 
 
 First, For what reason we pronounce it necessary 
 that everything whose existence has a beginning 
 should also have a cause ? 
 
 Secondly, Why we conclude that such particular 
 causes must necessariiy have such particular effects ; 
 and what is the nature of that inference we draw from 
 the one to the other, and of the belief we repose in it ? 
 
Sec. III.] OF KNOWLEDGE AND PROBABILITV. 9I 
 
 SECTION III. 
 IV/iy a cause is a/ways necessary. 
 
 To begin with the first question concerning the 
 necessity of a cause : It is a general maxim in 
 philosophy that whatever begins to exist must have a 
 cause of existence. This is commonly taken for granted 
 in all reasonings, without any proof given or de- 
 manded. It is supposed to be founded on intuition, 
 and to be one of those maxims which, though they 
 may be denied with the lips, it is impossible for men in 
 their hearts really to doubt of. But all certainty arises 
 from the comparison of ideas, and from the discovery 
 of such relations as are unalterable so long as the ideas 
 continue the same. These relations are resemblance, 
 proportions in quantity and number, degrees of any qttal- 
 ity, and contrariety ; none of which are implied in this 
 proposition : Whatever has a beginning has also a cause 
 of existence. That proposition therefore is not in- 
 tuitively certain. 
 
 But here is an argument which proves at once that 
 the foregoing proposition is neither intuitively nor 
 demonstrably certain. As all distinct ideas are sepa- 
 rable from each other, and as the ideas of cause and 
 effect are evidently distinct, it will be easy for us to 
 conceive any object to be non-existent this moment 
 and existent the next, without conjoining to it the 
 distinct idea of a cause or productive principle. The 
 separation, therefore, of the idea of a cause from that 
 sf a beginning of existence is plainly possible for the 
 
92 THE PHILOSOPHY OF HUME. [Part III. 
 
 imagination ; and consequently the actual separation 
 of these objects is so far possible that it implies no con- 
 tradiction nor absurdity, and is therefore incapable of 
 being refuted by any reasoning from mere ideas ; with- 
 out which it is impossible to demonstrate the necessity 
 of a cause. 
 
 Accordingly we shall find upon examination that 
 every demonstration which has been produced for the 
 necessity of a cause is fallacious and sophistical. All 
 the points of time and place, * say some philosophers, 
 in which we can suppose any object to begin to exist, 
 are in themselves equal ; and unless there be some 
 cause which is peculiar to one time and to one place, 
 and which by that means determines and fixes the ex- 
 istence, it must remain in eternal suspense ; and the 
 object can never begin to be, for want of something to 
 fix its beginning. But I ask, Is there any more diffi- 
 culty in supposing the time and place to be fixed 
 without a cause than to suppose the existence to be 
 determined in that manner ? The first question that 
 occurs on this subject is always whether the object 
 shall exist or not. The next, 7iL<hen and where it shall 
 begin to exist. If the removal of a cause be intuitively 
 absurd in the one case, it must be so in the other : 
 and if that absurdity be not clear without a proof in 
 the one case, it will equally require one in the other. 
 The absurdity, then, of the one supposition can never 
 be a proof of that of the other; since they are both 
 upon the same footing and must stand or fall by the 
 same reasoning. 
 
 The second argument f which I find used on this 
 *Mr. Hoblh-s. f Dr. C7,;;,(-c and others. 
 
Sec. III.] OF KNOWLEDGE AND PROBABILITY. 93 
 
 head labors under an equal difficulty. Everything, it 
 is said, must have a cause ; for if anything wanted a 
 cause // would produce itself ; that is, exist before it 
 existed ; which is impossible. But this reasoning is 
 plainly unconclusive ; because it supposes that in our 
 denial of a cause we still grant what we expressly 
 deny, viz. : that there must be a cause ; which therefore 
 is taken to be the object itself ; and /Mi, no doubt, 
 is an evident contradiction. But to say that any- 
 thing is produced, or, to express myself more properly, 
 comes into existence, without a cause, is not to affirm 
 that it is itself its own cause ; but on the contrary, in 
 excluding all external causes, excludes a foi-iiori the 
 thing itself which is created. An object that exists 
 absolutely without any cause certainly is not its own 
 cause ; and when you assert that the one follows from 
 the other you suppose the very point in question, and 
 take it for granted that it is utterly impossible any- 
 thing can ever begin to exist without a cause, but that 
 upon the exclusion of one productive principle we 
 must still have recourse to another. 
 
 It is exactly the same case with the * third argu- 
 ment which has been employed to demonstrate the 
 necessity of a cause. Whatever is produced without 
 any cause is produced by nothing ; or, in other words, 
 has nothing for its cause. But nothing can never be 
 a cause, no more than it can be something, or equal 
 to two right angles. By the same intuition that we 
 perceive nothing not to be equal to two right angles, 
 or not to be something, we perceive that it can never 
 
 * Mr. Locke. 
 
94 THE PHILOSOPHY OF HUME. [Part III. 
 
 be a cause ; and consequently must perceive that 
 every object has a real cause of its existence. 
 
 I believe it will not be necessary to employ many 
 words in showing the weakness of this argument, after 
 what I have said of the foregoing. They are all of 
 them founded on the same fallacy, and are derived 
 from the same turn of thought. It is sufficient only 
 to observe that when we exclude all causes we really 
 do exclude them, and neither suppose nothing nor the 
 object itself to be the causes of the existence ; and 
 consequently can draw no argument from the absurd- 
 ity of these suppositions to prove the absurdity of that 
 exclusion. If everything must have a cause, it fol- 
 lows that upon the exclusion of other causes we must 
 accept of the object itself or of nothing as causes. 
 But it is the very point in question, whether every- 
 thing must have a cause or not ; and therefore, ac- 
 cording to all just reasoning, it ought never to be 
 taken for granted. 
 
 They are still more frivolous who say that every 
 effect must have a cause, because it is implied in the 
 very idea of effect. Every effect necessarily presup- 
 poses a cause ; effect being a relative term, of which 
 cause is the correlative. But this does not prove 
 that every being must be preceded by a cause ; no 
 more than it follows because every husband must 
 have a wife that therefore every man must be married. 
 The true state of the question is, whether every object 
 which begins to exist must owe its existence to a 
 cause ; and this I assert to be neither intuitively nor 
 demonstratively certain, and hope to have proved it 
 sufficiently by the foregoing arguments. 
 
SecS. IV, v.] OF KNOWLEDGE AND PROBABILITY. 95 
 
 Since it is not from knowledge or any scientific 
 reasoning that we derive the opinion of the necessity 
 of a cause to every new production, that opinion must 
 necessarily arise from observation and experience. 
 The next question, then, should naturally be, how ex- 
 perience gives rise to such a principle ? But as I find it 
 will be more convenient to sink this question in the 
 following : Why we conclude that such particular 
 causes must necessarily have such particular effects, and 
 why we form an inference from one to another 1 we 
 shall make that the subject of our future enquiry. It 
 will, perhaps, be found in the end that the same 
 answer will serve for both questions. 
 
 SECTIONS IV., V. 
 
 Of the component parts of our reasonings concerning 
 cause and effect, and of the impressions of the senses 
 and memory. 
 
 Though the mind in its reasonings from causes or 
 effects carries its view beyond those objects which it 
 sees or remembers, it must never lose sight of them 
 entirely, nor reason merely upon its own ideas with- 
 out some mixture of impressions, or at least of ideas 
 of the memory which are equivalent to impressions. 
 When we infer effects from causes, we must establish 
 the existence of these causes ; which we have only two 
 ways of doing : either by an immediate perception of 
 our memory or senses, or by an inference from other 
 causes ; which causes again we must ascertain in the 
 same manner, either by a present impression, or by an 
 
96 THE PHILOSOPHY OF HUJIE. [Pakt 111. 
 
 inference from ^//^/r causes, and so on, till we arrive at 
 some object which we see or remember. It is impossi- 
 ble for us to carry on our inferences in i?tfiiiitum ; and 
 the only thing that can stop them is an impression of 
 the memory or senses, beyond which there is no room 
 for doubt or enquiry. 
 "^ Here therefore we have three things to explain, viz.: 
 First, the original impression. Secondly, the transi- 
 tion to the idea of the connected cause or effect. 
 Thirdly, the nature and qualities of that idea. 
 ,__,^ [i] As to those impressions which arise from the 
 — senses, their ultimate cause is, in my opinion, perfectly 
 inexplicable by human reason, and it will always be 
 impossible to decide with certainty whether they 
 arise immediately from the object, or are produced by 
 the creative power of the mind, or are derived from 
 the author of our being. Nor is such a question any 
 way material to our present purpose. We may draw 
 inferences from the coherence of our perceptions, 
 whether they be true or false ; whether they represent 
 nature justly, or be mere illusions of the senses. 
 
 When we search for the characteristic which dis- 
 tinguishes the memory from the imagination, we must 
 immediately perceive that it cannot lie in the simple 
 ideas it presents to us ; since both these faculties bor- 
 row their simple ideas from the impressions, and can 
 never go beyond these original perceptions. These 
 faculties are as little distinguished from each other by 
 the arrangement of their complex ideas ; it being im- 
 possible to recall the past impressions in order to 
 compare them with our present ideas and see whether 
 their arrangement be exactly similar. Since therefore 
 
Sec. VI.] OF KNOWLEDGE AND PROBABILITY. 97 
 
 the memory is known neither by the order of its 
 complex ideas nor the nature of its simple ones, it 
 follows that the difference betwixt it and the imagi- 
 nation lies in its superior force and vivacity. A man 
 may indulge his fancy in feigning any past scene of 
 adventures ; nor would there be any possibility of dis- 
 tinguishing this from a remembrance of a like kind, 
 were not the ideas of the imagination fainter and more 
 obscure. 
 
 Thus it appears that the belief or assent, which always 
 attends the memory and senses, is nothing but the 
 vivacity of those perceptions they present ; and that 
 this alone distinguishes them from the imagination. 
 To believe is in this case to feel an immediate impres- 
 sion of the senses, or a repetition of that impression 
 in the memory. It is merely the force and liveliness 
 of the perception which constitutes the first act of 
 the judgment, and lays the foundation of that reason- 
 ing which we build upon it when we trace the rela- 
 tion of cause and effect. 
 
 SECTION VI. 
 [2] Of the inference from the impression to the idea. 
 
 It is easy to observe that, in tracing this relation, 
 the inference we draw from cause to effect is not de- 
 rived merely from a survey of these particular objects 
 and from such a penetration into their essences as 
 may discover the dependence of the one upon the 
 other. There is no object which implies the exist- 
 ence of any other if we consider these objects in 
 
gS THE PHILOSOPHY OF HU^IE. [PART III. 
 
 themselves and never look beyond the ideas which 
 we form of them. Such an inference would amount 
 to knowledge, and would imply the absolute contradic- 
 tion and impossibility of conceiving anything differ- 
 ent. But, as all distinct ideas are separable, it is evi- 
 dent there can be no impossibility of that kind. 
 When we pass from a present impression to the idea 
 of any object, we might possibly have separated the 
 idea from the impression, and have substituted any 
 other idea in its room. 
 
 It is therefore by experience only that we can infer 
 the existence of one object from that of another. 
 Thus we remember to have seen that species of object 
 we call flame, and to have felt that species of sensa- 
 tion we call heat. We likewise call to mind their con- 
 ... 
 ( stant conjunction in all past instances. Without any 
 
 farther ceremony, we call the one cause and the other 
 effect, and infer the existence of the one from that of 
 the other. In all those instances from which we learn 
 the conjunction of particular causes and effects, both 
 the causes and effects have been perceived by the 
 senses and are remenibered : but in all cases wherein 
 we reason concerning them there is only one per- 
 ceived or remembered, and the other is supplied in 
 conformity to our past experience. 
 
 Thus in advancing we have insensibly discovered a 
 new relation betwixt cause and effect when we least 
 expected it and were entirely employed upon another 
 subject. This relation is their constant conjunc- 
 TiON. Contiguity and succession are not sufificient to 
 make us pronounce any two objects to be cause and 
 effect, unless we perceive that these two relations are 
 
Sec. VI, ] OF KNOWLEDGE AND PROBABILITY. 99 
 
 preserved in several instances. We may now see the 
 advantage of quitting the direct survey of this rela- 
 tion in order to discover the nature of that necessary 
 connection which makes so essential a part of it. Hav- 
 ing found that after the discovery of the constant 
 conjunction of any objects we always draw an infer- 
 ence from one object to another, we shall now examine 
 the nature of that inference and of the transition 
 from the impression to the idea. Perhaps it will ap- 
 pear in the end that the necessary connection depends , 
 on the inference, instead of the inference's depending ,' 
 on the necessary connection. 
 
 Since it appears that the transition from an impres- 
 sion present to the memory or senses to the idea of an 
 object which we call cause or effect is founded on 
 past experience, and on our remembrance of their con- 
 stant conjunction, the next question is, AVhether experi- 
 ence produces the idea by means of the understanding 
 or of the imagination ; whether we are determined by 
 reason to make the transition, or by a certain associa- 
 tion and relation of perceptions ? If reason deter- ^ 
 mined us, it would proceed upon that principle that 
 instances of which we have had no experience must 
 resemble those of which we have had experience, and that 
 the course of nature continues always uniformly the same. 
 
 The arguments upon which such a proposition may 
 be supposed to be founded must be derived either 
 from knowledge ox probability. Our foregoing method 
 of reasoning will easily convince us that there can be 
 no demonstrative arguments to prove that those instances 
 of which we have had no experience resemble those of 
 which W^ hav? had experience. We can at least con- 
 
lOO THE PHILOSOPHY OF HUME. [PART III. 
 
 ceive a change in the course of nature ; which suffi- 
 ciently proves that such a change is not absolutely 
 impossible. To form a clear idea of anything is an 
 undeniable argument for its possibility, and is alone a 
 refutation of any pretended demonstration against it. 
 Probability is founded on the presumption of a re- 
 semblance betwixt those objects of which we have had 
 experience and those of which we have had none ; 
 and therefore it is impossible this presumption can 
 arise from probability. The same principle cannot be 
 both the cause and effect of another ; and this is, 
 perhaps, the only proposition concerning that relation 
 which is either intuitively or demonstratively certain. 
 Thus not only our reason fails us in the discovery 
 of the ttltimate connection of causes and effects, but 
 even after experience has informed us of their constant 
 conjunction it is impossible for us to satisfy ourselves 
 by our reason why we should extend that experience 
 beyond those particular instances which have fallen 
 under our observation. AVe suppose, but are never 
 able to prove, that there must be a resemblance betwixt 
 those objects of which we have had experience and 
 those which lie beyond the reach of our discovery. 
 
 When the mind, therefore, passes from the idea or 
 impression of one object to the idea or belief of an- 
 other, it is not determined by reason, but by certain 
 principles which associate together the ideas of these 
 objects and unite them in the imagination. Had 
 ndeas no more union in the fancy than objects seem 
 to have to the understanding, we could never draw 
 any inference from causes to effects, nor repose belief 
 in any matter of fact. The inference, therefore, 
 
Sec. VII.] OF KNOWLEDGE AND PROBABILITY. lOI 
 
 depends solely on the union of ideas. When the 
 impression of one object becomes present to us, we 
 immediately form an idea of its usual attendant ; and 
 consequently we may establish this as one part of the 
 definition of an opinion or belief, that it is an idea 
 related to or associated with a present impression. 
 
 Thus, though causation be a. philosophical relation, as 
 implying contiguity, succession, and constant conjunc- 
 tion, yet it is only so far as it is a natural relation, and 
 produces an union among our ideas, that we are unable 
 to reason upon it, or draw any inference from it. 
 
 SECTION VII. 
 
 [3] Of the nature of the idea or belief. 
 
 It is evident that all reasonings from causes or 
 effects terminate in conclusions concerning matter of 
 fact ; that is, concerning the existence of objects or 
 of their qualities. It is also evident that the idea of 
 existence is nothing different from the idea of any 
 object, and that when after the simple conception of 
 anything we would conceive it as existent, we in 
 reality make no addition to or alteration on our first 
 idea. Thus, when we affirm that God is existent, we 
 simply form the idea of such a being as he is repre- 
 sented to us ; nor is the existence which we attribute 
 to him conceived by a particular idea which we join 
 to the idea of his other qualities and can again sepa- 
 rate and distinguish from them. But I go farther ; 
 and, not content with asserting that the conception of 
 
102 THE PHILOSOPHY OF HUME. [PART III. 
 
 the existence of any object is no addition to the simple 
 conception of it, I likewise maintain that the belief 
 of the existence joins no new ideas to those which 
 compose the idea of the object. When I think of 
 God, when I think of him as existent, and when I 
 believe him to be existent, my idea of him neither 
 increases nor diminishes. But, as it is certain there is 
 a great difference betwixt the simple conception of 
 the existence of an object and the belief of it, and as 
 this difference lies not in the parts or composition of 
 the idea which we conceive, it follows that it must lie 
 in the ma)uier in which we conceive it. 
 
 I therefore ask, Wherein consists the difference 
 betwixt believing and disbelieving any proposition ? 
 The answer is easy with regard to propositions that 
 are proved by intuition or demonstration. In that 
 case, the person who assents not only conceives the 
 ideas according to the proposition, but is necessarily 
 determined to conceive them in that particular 
 manner, either immediately or by the interposition of 
 ,other ideas. Whatever is absurd is unintelligible ; 
 nor is it possible for the imagination to conceive any- 
 thing contrary to a demonstration. But, as in reason- 
 ings from causation and concerning matters of fact 
 this absolute necessity cannot take place, and the 
 imagination is free to conceive both sides of the ques- 
 tion, I still ask. Wherein consists the differerice betwixt 
 incredulity and beliefs since in both cases the con- 
 ception of the idea is equally possible and requisite. 
 
 It is confessed that in all cases wherein we dissent 
 from any person we conceive both sides of the ques- 
 tion ; but, as we can believe only one, it evidently 
 
Sec. VII.] OF KNOWLEDGE AND PROBABlLltV. IO3 
 
 foliovvs that the belief must make some difference 
 betwixt that conception to which we assent and that 
 from which we dissent. We may mingle, and unite, 
 and separate, and confound, and vary our ideas in a 
 hundred different ways ; but, until there appears some 
 principle which fixes one of these different situations, 
 we have in reality no opinion : and this principle, as 
 it plainly makes no addition to our precedent ideas, 
 can only change the manner of our conceiving them. 
 
 When you would any way vary the idea of a par- 
 ticular object, you can only increase or diminish its 
 force and vivacity. If you make any other change 
 on it, it represents a different object or impression. 
 The case is the same as in colors. A particular shade 
 of any color may acquire a new degree of liveliness 
 or brightness without any other variation. But when 
 you produce any other variation, it is no longer the 
 same shade or color. So that, as belief does nothing 
 but vary the manner in which we conceive any object, 
 it can only bestow on our ideas an additional force 
 and vivacity. An opinion, therefore, or belief may 
 be most accurately defined, A lively idea related 
 I TO OR associated with a present impression. 
 
 Here are the heads of those arguments which lead 
 us to this conclusion. When we infer the existence 
 of an object from that of others, some object must 
 always be present either to the memory or senses in 
 order to be the foundation of our reasoning ; since 
 the mind cannot run up with its inferences in in- 
 finitum. Reason can never satisfy us that the exist- 
 ence of any one object does ever imply that of an- 
 other ; so that when we pass from the impression of 
 
104 THE PHILOSOPHY OF HUME. [Part III. 
 
 one to the idea or belief of another, we are not 
 determined by reason, but by custom or a principle of 
 association. But belief is somewhat more than a 
 simple idea. It is a particular manner of forming an 
 idea : and as the same idea can only be varied by a 
 variation of its degrees of force and vivacity, it 
 follows, upon the whole, that belief is a lively idea 
 produced by a relation to a present impression, 
 according to the foregoing definition. 
 
 SECTION VIII. 
 Of the causes of belief. 
 
 I vi^ouLD willingly establish it as a general maxim 
 in the science of human nature that 7vhen any im- 
 pression becomes present to us, it ?iot only transports the 
 mifid to such ideas as are related to it, but likewise com- 
 municates to them a share of its force and vivacity. 
 
 Upon the appearance of the picture of an absent 
 friend, our idea of him is evidently enlivened by the 
 resemblance, and every passion which that idea occa- 
 sions, whether of joy or sorrow, acquires new force 
 and vigor. 
 
 The thinking on any object readily transports the 
 mind to what is contiguous; but it is only the actual 
 presence of an object that transports it with a superior 
 vivacity. When I am a few miles from home, what- 
 ever relates to it touches me more nearly than when 
 I am two hundred leagues distant ; though even at 
 that distance the reflecting on anything in the neigh- 
 
Sec. VIII.jOF KNOWLEDGE AND PROBABILITY. I05 
 
 borhood of my friends and family naturally produces 
 an idea of them. 
 
 No one can doubt but causation has the same in- 
 fluence as the other two relations of resemblance and 
 contiguity. The objects it presents are fixed and un- 
 alterable. The impressions of the memory never 
 change in any considerable degree ; and each impres- 
 sion draws along with it a precise idea, which takes 
 its place in the imagination as something solid and 
 real, certain and invariable. The thought is always 
 determined to pass from the impression to the idea, 
 and from that particular impression to that particular 
 idea, without any choice or hesitation. 
 
 Contiguity and resemblance have an effect much 
 inferior to causation ; but still have some effect, and 
 augment the conviction of any opinion and the vivac- 
 ity of any conception. 
 
 Thus all probable reasoning is nothing but a species 
 of sensation. It is not solely in poetry and music we 
 must follow our taste and sentiment, but likewise in 
 philosophy. When I am convinced of any principle, 
 it is only an idea which strikes more strongly upon 
 me. When I give the preference to one set of argu- 
 ments above another, I do nothing but decide from 
 my feeling concerning the superiority of their influ- 
 ence. Objects have no discoverable connection to- 
 gether ; nor is it from any other principle but custom 
 operating upon the imagination that we can draw any 
 inference from the appearance of one to the existence 
 of another. 
 
Io6 THE PHILOSOPHY OF HUME. [Part HI, 
 
 SECTIONS XL, XII., XIII. 
 Of probability. 
 
 But, in order to bestow on this system its full force 
 and evidence, we must carry our eye from it a moment 
 to consider its consequences, and explain from the 
 same principles some other species of reasoning which 
 are derived from the same origin. 
 
 Those philosophers who have divided human reason 
 into ktiowledge and probability, and have defined the 
 first to be that evidence which arises from the compari- 
 son of ideas, are obliged to comprehend all our argu- 
 ments from causes or effects under the general term 
 of probability. But though every one be free to use 
 his terms in what sense he pleases, and accordingly 
 in the precedent part of this discourse I have fol- 
 lowed this method of expression; it is however cer- 
 tain that in common discourse we readily affirm that 
 many arguments from causation exceed probability 
 and may be received as a superior kind of evidence. 
 One would appear ridiculous who would say that it 
 is only probable the sun will rise to-morrow or that 
 all men must die ; though it is plain we have no fur- 
 ther assurance of these facts than what experience 
 affords us. For this reason, it would perhaps be more 
 convenient, in order at once to preserve the common 
 signification of words and mark the several degrees 
 of evidence, to distinguish human reason into three 
 kinds, viz., that from knowledge, from proofs, and from 
 
Secs.xI, XII.XIII.] Knowledge and probability. 107 
 
 probabilities. By knowledge I mean the assurance 
 arising from the comparison of ideas. By proofs, 
 those arguments which are derived from the relation 
 of cause and effect, and which are entirely free from 
 doubt and uncertainty. By probability, that evidence 
 which is still attended with uncertainty. It is this 
 last species of reasoning I proceed to examine. 
 
 It is commonly allowed by philosophers that what 
 the vulgar call chance is nothing but a secret and 
 concealed cause. That species of probability, there- 
 fore, is what we must chiefly examine. 
 
 The probabilities of causes are of several kinds, but 
 are all derived from the same origin, viz., the associa- 
 tion of ideas to a present impression. As the habit 
 which produces the association arises from the fre- 
 quent conjunction of objects, it must arrive at its per- 
 fection by degrees, and must acquire new force from 
 each instance that falls under our observation. The 
 first instance has little or no force ; the second makes 
 some addition to it ; the third becomes still more 
 sensible : and it is by these slow steps that our judg- 
 ment arrives at a full assurance. But before it attains 
 this pitch of perfection it passes through several infe- 
 rior degrees, and in all of them is only to be esteemed 
 a presumption or probability. The gradation, there- 
 fore, from probabilities to proofs is in many cases 
 insensible ; and the difference betwixt these kinds of 
 evidence is more easily perceived in the remote de- 
 grees than in the near and contiguous. 
 
 But, secondly, when in considering past experiments 
 we find them of a contrary nature, the habit or deter- 
 mination of the mind to transfer the past to the future 
 
lo8 THE PHILOSOPHY OF HUME. [Part 111. 
 
 and expect for the future the same train of objects to 
 which we have been accustomed, though full and per- 
 fect in itself, presents us with no steady object, but 
 offers us a number of disagreeing images in a certain 
 order and proportion. The first impulse, therefore, is 
 here broke into pieces, and diffuses itself over all 
 those images, of which each partakes an equal share 
 of that force and vivacity that is derived from the im- 
 pulse. Any of these past events may happen again ; 
 and we judge that when they do happen they will be 
 mixed in the same proportion as in the past. 
 
 Suppose, for instance, I have found by long obser- 
 vation that, of twenty ships which go to sea, only 
 nineteen return. Suppose I see at present twenty 
 ships that leave the port : I transfer my past experi- 
 ence to the future, and represent to myself nineteen 
 of these ships as returning in safety, and one as per- 
 ishing. Concerning this there can be no difficulty. 
 But, as we frequently run over those several ideas of 
 past events in order to form a judgment concerning 
 one single event which appears uncertain, this con- 
 sideration must change the first form of our ideas, 
 and draw together the divided images presented by 
 experience ; since it is to // we refer the determina- 
 tion of that particular event upon which we reason. 
 Many of these images are supposed to concur, and a 
 superior number to concur on one side. These agree- 
 ing images unite together and render the idea more 
 strong and lively, not only than a mere fiction of the 
 imagination, but also than any idea which is sup- 
 ported by a lesser number of experiments. Each new 
 experiment is as a new stroke of the pencil, which be- 
 
Secs. XI, XII, XIII.] KNOWLEDGE AND PROBAEILITY. 109 
 
 Stows an additional vivacity on the colors without 
 either multiplying or enlarging the figure. 
 
 This is the manner in which past experiments con- 
 cur when they are transferred to any future event. 
 As to the manner of their opposition, it is evident that, 
 as the contrary views are incompatible with each other 
 and it is impossible the object can at once exist con- 
 formable to both of them, their influence becomes mu- 
 tually destructive, and the mind is determined to the 
 superior only with that force which remains after sub- 
 tracting the inferior. 
 
 But, beside these two species of probability which 
 are derived from an imperfect experience and from 
 contrary causes, there is a third, arising from Analogy 
 which differs from them in some material circum- 
 stances. According to the hypothesis above explained 
 all kinds of reasoning from causes or effects are 
 founded on two particulars, viz., the constant con- 
 junction of any two objects in all past experience, 
 and the resemblance of a present object to any one 
 of them. The effect of these two particulars is that 
 the present object invigorates and enlivens the imagi- 
 nation ; and the resemblance along with the constant 
 union conveys this force and vivacity to the related 
 idea ; which we are therefore said to believe, or assent 
 to. If you weaken either the union or resemblance, 
 you weaken the principle of transition, and, of conse- 
 quence, that belief which arises from it. The vivacity 
 of the first impression cannot be fully conveyed to 
 the related idea, either where the conjunction of their 
 objects is not constant, or where the present impres- 
 sion does not perfectly resemble any of those whose 
 
116 tHE PHILOSOPHV Of HUME. [Part III. 
 
 union we are accustomed to observe. In those prob- 
 abilities of chance and causes above explained it is 
 the constancy of the union which is diminished ; and 
 in the probability derived from analogy, it is the re- 
 semblance only which is affected. Without some 
 degree of resemblance, as well as union, it is impos- 
 sible there can be any reasoning : but, as this re- 
 semblance admits of many different degrees, the 
 reasoning becomes proportionably more or less firm 
 and certain. An experiment loses of its force when 
 transferred to instances which are not exactly re- 
 sembling ; though it is evident it may still retain as 
 much as may be the foundation of probability, as long 
 as there is any resemblance remaining. 
 
 Thus it appears, upon the whole, that every kind of 
 opinion or judgment which amounts not to knowl- 
 edge is derived entirely from the force and vivacity 
 of the perception, and that these qualities constitute 
 in the mind what we call the belief of the existence 
 of any object. This force and this vivacity are most 
 conspicuous in the memory ; and therefore our con- 
 fidence in the veracity of that faculty is the greatest 
 imaginable, and equals in many respects the assurance 
 of a demonstration. The next degree of these quali- 
 ties is that derived from the relation of cause and 
 effect ; and this too is \ery great, especially when, the 
 conjunction is found by experience to be perfectly 
 constant, and when the object which is present to 
 us exactly resembles those of which we have had 
 experience. But below this degree of evidence there 
 are many others, which have an influence on the 
 passions and imagination proportioned to that degree 
 
Sec. XIV.] OF knowledgf, and prouabilitv. hi 
 
 of force and vivacity which they communicate to the 
 ideas. It is by habit we make the transition from 
 cause to effect ; and ii is from some present impres- 
 sion we borrow tliat vivacity which we diffuse over 
 the correlative idea. But when we have not observed 
 a sufficient number of instances to produce a strong 
 habit ; or when these instances are contrary to each 
 other ; or when the resemblance is not exact ; or 
 the present impression is faint and obscure ; or the 
 experience in some measure obliterated from tlie 
 memory ; or the connection dependent on a long 
 chain of objects ; or the inference derived from gen- 
 eral rules, and yet not conformable to them : In all 
 these cases the evidence diminishes by the diminution 
 of the force and intenseness of the idea. This there- 
 fore is the nature of the judgment and probability. 
 
 SECTION XIV. 
 
 Of the idea of necessary connection* 
 
 Having thus explained the manner in which we 
 reason beyond cur immediate impressions, and conclude 
 that such particular causes must have such particular 
 effects, we must now return upon our footsteps to 
 examine that question which f first occurred to us, 
 and which we dropped in our way, viz.. What is our 
 idea of necessity when we say that tivo objects are neces- 
 sarily connected together 7 Upon this head I repeat 
 
 * [Tliis section and Sections v. and vi. of Part I. are inserted 
 in full.— El).] 
 I Section IJ. 
 
112 THE PHILOSOPHY OF HUME. [Part III. 
 
 what I have often had occasion to observe, that, as we 
 have no idea that is not derived from an impression, 
 we must find some impression that gives rise to this 
 idea of necessity, if we assert we have really such an 
 idea. In order to this, I consider in what objects 
 necessity is commonly supposed to lie ; and, finding 
 that it is always ascribed to causes and effects, I 
 turn my eye to two objects supposed to be placed in 
 that relation, and examine them in all the situations 
 of which they are susceptible. I immediately per- 
 ceive that they are contiguous in time and place and 
 that the object we call cause pi-ecedes the other we 
 call effect. In no one instance can I go any farther, 
 nor is it possible for me to discover any third relation 
 betwixt these objects. I therefore enlarge my view 
 to comprehend several instances where I find like 
 objects always existing in like relations of contiguity 
 and succession. At first sight this seems to serve but 
 little to my purpose. The reflection on several in- 
 stances only repeats the same objects, and therefore 
 can never give rise to a new idea. But upon farther 
 inquiry I find that the repetition is not in every par- 
 ticular the same, but produces a new impression, and 
 by that means the idea which I at present examine. 
 For, after a frequent repetition, I find that upon the 
 appearance of one of the objects the mind is de- 
 termined by custom to consider its usual attendant, 
 and to consider it in a stronger light upon account of 
 its relation to the first object. It is this impression, 
 then, or determination, which affords me the idea of 
 necessity. 
 
 I doubt not but these consequences will at first 
 
Sec. XIV.] OF kxowlelge and probability. 113 
 
 sight be received without difficulty, as being evident 
 deductions from principles which we have already 
 established and which we have often employed in 
 our reasonings. This evidence, both in the first prin- 
 ciples and in the deductions, may seduce us unwarily 
 into the conclusion, and make us imagine it contains 
 nothing extraordinary nor worthy of our curiosity. 
 But, though such an inadvertence may facilitate the 
 reception of this reasoning, it will make it be the 
 more easily forgot ; for which reason I think it proper 
 to give warning that I have just now examined one 
 of the most sublime questions in philosophy, viz., that 
 concernitig the power and efficacy of causes ; where all 
 the sciences seem so much interested. Such a warn- 
 ing will naturally rouse up the attention of the reader 
 and make him desire a more full account of my doc- 
 trine, as well as of the arguments on which it is 
 founded. This request is so reasonable that I can- 
 not refuse complying with it ; especially as I am 
 hopeful that these principles, the more they are ex- 
 amined, will acquire the more force and evidence. 
 
 There is no question which, on account of its 
 importance as well as difficulty, has caused more dis- 
 putes both among ancient and modern philosophers 
 than this concerning the efficacy of causes, or that 
 quality which makes them be followed by their effects. 
 But, before they entered upon these disputes, methinks 
 it would not have been improper to have examined 
 what idea we have of that efficacy which is the sub- 
 ject of the controversy. This is what I find princi- 
 pally wanting in their reasonings, and what I shall 
 here endeavor to supply. 
 
114 THE PHILOSOPHY OF HUME. [Paj^tIH. 
 
 I begin with observing that the terms of efficacy, 
 agency, power, force, energy, necessity, connection, and 
 productive quality are all nearly synonymous ; and 
 therefore it is an absurdity to employ any of them in de- 
 fining the rest. By this observation we reject at once 
 all the vulgar definitions which philosophers have 
 given of power and efficacy ; and, instead of searching 
 for the idea in these definitions, must look for it in 
 the impressions from which it is originally derived. If 
 it be a compound idea, it must arise from compound 
 impressions; if simple, from simple impressions. 
 
 I believe the most general and most popular ex- 
 plication of this matter is to say *that, finding from 
 experience that there are several new productions in 
 matter, such as the motions and variations of body, 
 and concluding that there must somewhere be a power 
 capable of producing them, we arrive at last by this 
 reasoning at the idea of power and efficacy. But, to 
 be convinced that this explication is more popular 
 than philosophical, we need but reflect on two very 
 obvious principles. First, that reason alone can 
 never give rise to any original idea; and secondly, that 
 reason, as distinguished from experience, can never 
 make us conclude that a cause or productive quality 
 is absolutely requisite to every beginning of existence. 
 Both these considerations have been sufficiently ex- 
 plained ; and therefore shall not at present be any 
 farther insisted on. 
 
 I shall only infer from them that, since reason can 
 never give rise to the idea of efficacy, that idea must be 
 
 * See Mr, Locke : chapter of power, 
 
Sec. XIV.] OF knowledge and probability. 115 
 
 derived from experience, and from some particular in- 
 stances of this efficacy which make their passage into 
 the mind by the common channels of sensation or re- 
 flection. Ideas always represent their objects or im- 
 pressions ; and, vice versa, there are some objects 
 necessary to give rise to every idea. If we pretend, 
 therefore, to have any just idea of this efficacy, we 
 must produce some instance wherein the efficacy is 
 plainly discoverable to the mind, and its operations 
 obvious to our consciousness or sensation. By the 
 refusal of this we acknowledge that the idea is im- 
 possible and imaginary, since the principle of innate 
 ideas, which alone can save us from this dilemma, has 
 been already refuted and is now almost universally 
 rejected in the learned world. Our present business, 
 then, must be to find some natural production where 
 the operation and efficacy of a cause can be clearly 
 conceived and comprehended by the mind without 
 any danger of obscurity or mistake. 
 
 In this research we meet with very little encourage- 
 ment from that prodigious diversity which is found in 
 the opinions of those philosophers who have pre- 
 tended to explain the secret force and energy of 
 causes.* There are some who maintain that bodies 
 operate by their substantial form ; others, by their ac- 
 cidents or qualities ; several, by their matter and 
 form ; some, by their form and accidents ; others, by 
 certain virtues and faculties distinct from all this. 
 All these sentiments again are mixed and varied in 
 a thousand different ways ; and form a strong pre- 
 
 * Sf-e fariher Malbranche, Book VI., part II., chap, iii., ar)(3 
 J^e illustratitnis upon it, 
 
Il6 THE PHILOSOPHY OF HUME. [Part III. 
 
 sumption that none of them have any solidity or evi- 
 dence, and that the supposition of an efficacy in any 
 of the known quaUties of matter is entirely without 
 foundation. This presumption must increase upon 
 us when we consider that these principles of sub- 
 stantial forms, and accidents, and faculties are not in 
 reality any of the known properties of bodies, but are 
 perfectly unintelligible and inexplicable. For it is 
 evident philosophers would never have had recourse 
 to such obscure and uncertain principles had they 
 met with any satisfaction in such as are clear and in- 
 telligible ; especially in such an affair as this, which 
 must be an object of the simplest understanding, if 
 not of the senses. Upon the whole, we may conclude 
 that it is impossible in any one instance to show the 
 principle in which the force and agency of a cause is 
 placed, and that the most refined and most vulgar 
 understandings are equally at a loss in this particular. 
 If any one think proper to refute this assertion, he 
 need not put himself to the trouble of inventing any 
 long reasonings ; but may at once show us an instance 
 of a cause where we discover the power or operating 
 principle. This defiance we are obliged frequently to 
 make use of, as being almost the only means of prov- 
 ing a negative in philosophy. 
 
 The small success which has been met with in all 
 the attempts to fix this power has at last obliged phi- 
 losophers to conclude that the ultimate force and 
 efficacy of nature is perfectly unknown to us, and that 
 it is in vain we search for it in all the known qualities 
 of matter. In this opinion they .ire almost unanimous ; 
 and it is only in the inference they draw from it that 
 
Sec. XIV.] OF knowledge and prob.vbility. 117 
 
 they discover any difference in their sentiments. For 
 some of them, as the Cartesians in particular, having 
 established it as a \.nnciple that we are perfectly ac- 
 quainted with the essence of matter, have very nat- 
 urally inferred that it is endowed with no efficacy, 
 and that it is impossible for it of itself to communi- 
 cate motion, or produce any of those effects which we 
 ascribe to it. As the essence of matter consists in 
 extension, and as extension implies, not actual motion, 
 but only mobility, they conclude that the energy 
 which produces the motion cannot lie in the ex- 
 tension. 
 
 This conclusion leads them into another, which 
 they regard as perfectly unavoidable. Matter, say 
 they, is in itself entirely unactive, and deprived of any 
 power by which it may produce, or continue, or com- 
 municate motion : but, since these effects are evident 
 to our senses, and since the power that produces them 
 must be placed somewhere, it must lie in the Deitv, 
 or that divine being who contains in his nature all 
 excellency and perfection. It is the deity, therefore, 
 who is the prime mover of the universe, and who not 
 only first created matter and gave it its original im- 
 pulse, but likewise by a continued exertion of omnipo- 
 tence supports its existence, and successively bestows 
 on it all those motions, and configurations, and qualities 
 with which it is endowed. 
 
 This opinion is certainly very curious and well 
 worth our attention ; but it will appear superfluous to 
 examine it in this place, if we reflect a moment on our 
 present purpose in taking notice of it. We have es- 
 tablished it as a principle that, as all ideas are derived 
 
Il8 THE PHILOSOPHY OF HUME. [PART III. 
 
 from impressions, or some precedent perceptions^ it is 
 impossible we can have any idea of power and efficacy, 
 unless some instances can be produced wherein this 
 power is perceived to exert itself. Now, as these in- 
 stances can never be discovered in body, the Cartesians, 
 proceeding upon their principle of innate ideas, have 
 had recourse to a supreme spirit or deity, whom they 
 consider as the only active being in the universe and 
 as the immediate cause of every alteration in matter. 
 But, the principle of innate ideas being allowed to be 
 false, it follows that the supposition of a deity can 
 serve us in no stead in accounting for that idea of 
 agency which we search for in vain in all the objects 
 which are presented to our senses or which we are 
 internally conscious of in our own minds. For, if 
 every idea be derived from an impression, the idea of 
 a deity proceeds from the same origin ; and, if no im- 
 pression, either of sensation or reflection, implies any 
 force or efficacy, it is equally impossible to discover 
 or even imagine any such active principle in the deity. 
 Since these philosophers, therefore, have concluded, 
 that matter cannot be endowed with any efficacious 
 principle, because it is impossible to discover in it 
 such a principle, the same course of reasoning should 
 determine them to exclude it from the supreme being. 
 Or, if they esteem that opinion absurd and impious, 
 as it really is, I shall tell them how they may avoid it ; 
 and that is by concluding from the very first that 
 they have no adequate idea of power or efficacy in any 
 object ; since neither in body nor spirit, neither in 
 superior nor inferior natures, are they able to discover 
 one single instance of it, 
 
Sec. XIV.' OF Knowledge aK'd probability. 119 
 
 The same conclusion is unavoidable upon the hy- 
 pothesis of those who maintain the efficacy of second 
 causes, and attribute a derivative, but a real, power 
 and energy to matter. For, as they confess that this 
 energy lies not in any of the known qualities of 
 matter, the difficulty still remains concerning the ori- 
 gin of its idea. If we have really an idea of power, we 
 may attribute power to an unknown quality : but, as it 
 is impossible that that idea can be derived from such 
 a quality, and as there is nothing in known qualities 
 which can produce it, it follows that we deceive our- 
 selves when we imagine we are possessed of any idea 
 of this kind, after the manner we commonly under- 
 stand it. All ideas are derived from, and represent, 
 impressions. We never have any impression that con- 
 tains any power or efficacy. We never therefore have 
 any idea of power. 
 
 Some have asserted that we feel an energy or 
 power in our mind ; and that, having in this manner 
 acquired the idea of power, we transfer that quality 
 to matter, where we are not able immediately to dis- 
 cover it. The motions of our body and the thoughts 
 and sentiments of our mind (say they) obey the will ; 
 nor do we seek any farther to acquire a just notion of 
 force or power. But, to convince us how fallacious 
 this reasoning is, we need only consider that the will, 
 being here considered as a cause, has no more a 
 discoverable connection with its effects than any 
 material cause has with its proper effect. So far 
 from perceiving the connection betwixt an act of voli- 
 tion and a motion of the body, it is allowed that no 
 effect is more inexplicable from the powers and 
 
120 tHE PHILOSOPHY OF HOME. [PART III. 
 
 essence of thought and matter. Nor is the empire 
 of the will over our mind more intelligible. The 
 effect is there distinguishable and separable from the 
 cause, and could not be foreseen without the experi- 
 ence of their constant conjunction. We have com- 
 mand over our mind to a certain degree, but beyond 
 that lose all empire over it : and it is evidently im- 
 possible to fix any precise bounds to our authority, 
 where we consult not experience. In short, the 
 actions of the mind are, in this respect, the same with 
 those of matter. We perceive only their constant 
 conjunction ; nor can we ever reason beyond it. No 
 internal impression has an apparent energy, more 
 than external objects have. Since, therefore, matter 
 is confessed by philosophers to operate by an un- 
 known force, we should in vain hope to attain an idea 
 of force by consulting our own minds.* 
 
 It has been established as a certain principle, that 
 general or abstract ideas are nothing but individual 
 ones taken in a certain light, and that, in reflecting 
 on any object, it is as impossible to exclude from our 
 thought all particular degrees of quantity and quality 
 as from the real nature of things. If we be possessed, 
 
 * The same imperfection attends our ideas of the Deity ; but 
 this can have no effect either on religion or morals. The order 
 of the universe proves an omnipotent mind ; that is, a mind 
 whose will is constantly attended \-i\\\\ the obedience of every 
 creature and being. Nothing more is requisite to give a foun- 
 dation to all the articles of religion, nor is it necessary we 
 should form a distinct idea of the force and energy of the su- 
 preme Being. [This note and the paragraph to which it is 
 added appeared originally in an appendi.K. — Ed.] 
 
Sec. XIV.] OF KNOWLEDGE AND PROBABILITY. 121 
 
 therefore, of any idea of power in general, we must 
 also be able to conceive some particular species of it ; 
 and, as power cannot subsist alone, but is always re- 
 garded as an attribute of some being or existence, we 
 must be able to place this power in some particular 
 being, and conceive that being as endowed with a 
 real force and energy, by which such a particular 
 effect necessarily results from its operation. We 
 must distinctly and particularly conceive the connec- 
 tion betwixt the cause and effect, and be able to 
 pronounce from a simple view of the one that it 
 must be followed or preceded by the other. This is 
 the true manner of conceiving a particular power in 
 a particular body ; and, a general idea being impos- 
 sible without an individual, where the latter is im- 
 possible it is certain the former can never exist. 
 Now nothing is more evident than that the human 
 mind cannot form such an idea of two objects as to 
 conceive any connection betwixt them, or compre- 
 hend distinctly that power or efficacy by which they 
 are united. Such a connection would amount to a 
 demonstration, and would imply the absolute impos- 
 sibility for the one object not to follow, or to be con- 
 ceived not to follow, upon the other : which kind of 
 connection has already been rejected in all cases. If 
 any one is of a contrary opinion and thinks he has 
 attained a notion of power in any particular object, I 
 desire he may point out to me that object. But till 
 I meet with such a one, which I despair of, I cannot 
 forbear concluding that, since we can never distinctly 
 conceive how any particular power can possibly reside 
 
122 THE PHltOSOPHY OP HUME. [Part HI. 
 
 in any particular object, we deceive ourselves in 
 imagining we can form any such general idea. 
 
 Thus, upon the whole, we may infer that when we 
 talk of any being, whether of a superior or inferior 
 nature, as endowed with a power or force propor- 
 tioned to any effect ; when we speak of a necessary 
 connection betwixt objects, and suppose that this 
 connection depends upon an efficacy or energy with 
 which any of these objects are endowed ; in all these 
 expressions, so applied, we have really no distinct 
 meaning, and make use only of common words, with- 
 out any clear and determinate ideas. But, as it is 
 more probable that these expressions do here lose 
 their true meaning by being im-oitg applied, than that 
 they never have any meaning, it will be proper to 
 bestow another consideration on this. subject, to see if 
 possibly we can discover the nature and origin of 
 those ideas we annex to them. 
 
 Suppose two objects to be presented to us, of which 
 the one is the cause and the other the effect; it is plain 
 that from the simple consideration of one or both 
 these objects we never shall perceive the tie by which 
 they are united, or be able certainly to pronounce 
 that there is a connection betwixt them. It is not, 
 therefore, from any one instance that we arrive at 
 the idea of cause and effect, of a necessary connec- 
 tion of power, of force, of energy, and of efficacy. 
 Did we never see any but particular conjunctions of 
 objects, entirely different from each other, we should 
 never be able to form any such ideas. 
 
 But again : suppose we observe several instances 
 in which the same objects are always conjoined to- 
 
Sec. XIV.] OF knowledgp. and probability. 123 
 
 gether, we immediately conceive a connection betwixt 
 them, and begin to draw an inference from one to an- 
 other. This multiplicity of resembling instances, 
 therefore, constitutes the very essence of power or 
 connection, and is the source from which the idea of 
 it arises. In order, then, to understand the idea of 
 power, we must consider that multiplicity ; nor do I 
 ask more to give a solution of that difficulty which 
 has so long perplexed us. For thus I reason. The 
 repetition of perfectly similar instances can never alone 
 give rise to an original idea, different from what is to 
 be found in any particular instance, as has been ob- 
 served, and as evidently follows from our fundamental 
 principle that all ideas are copied from impressions. 
 Since therefore the idea of power is a new original 
 idea, not to be found in any one instance, and which 
 yet arises from the repetition of several instances, it 
 follows that the repetition alone has not that effect, 
 but must either discover or produce something new 
 which is the source of that idea. Did the repetition 
 neither discover nor produce anything new, our ideas 
 might be multiplied by it, but would not be enlarged 
 above what they are upon the observation of one 
 single instance. Every enlargement, therefore, (such 
 as the idea of power or connection), which arises from 
 the multiplicity of similar instances, is copied from 
 some effects of the multiplicity, and will be perfectly 
 understood by understanding these effects. Wherever 
 we find anything new to be discovered or produced by 
 the repetition, there we must place the power, and 
 must never look for it in any other object. 
 
 But it is evident, in the first place, that the repeti- 
 
124 'I'Hr. PHILOSOPHV OF HUME. [Part III. 
 
 tion of like objects in like relations of succession and 
 contiguity discovers nothing new in any one of them ; 
 since we can draw no inference from it, nor make it a 
 subject either of our demonstrative or probable reason- 
 ings ; * as has been already proved. Nay, suppose we 
 could draw an inference, it would be of no conse- 
 quence in the present case; since no kind of reasoning 
 can give rise to a new idea, such as this of power is ; 
 but wherever we reason, we must antecedently be 
 possessed of clear ideas, which may be the objects of 
 our reasoning. The conception always precedes the 
 understanding ; and where the one is obscure the 
 other is uncertain ; where the one fails the other must 
 fail also. 
 
 Secondly, It is certain that this repetition of similar 
 objects in similar situations produces nothing new 
 either in these objects, or in any external body. For it 
 will readily be allowed that the several instances we 
 have of the conjunction of resembling causes and 
 effects are in themselves entirely independent, and 
 that the communication of motion which I see result 
 at present from the shock of two billiard-balls is 
 totally distinct from that which I saw result from 
 such an impulse a twelvemonth ago. These impulses 
 have no influence on each other. They are entirely 
 divided by time and place ; and the one might have 
 existed and communicated motion though the other 
 never had been in being. 
 
 There is, then, nothing new either discovered or 
 produced in any objects by their constant conjunc- 
 
 *Sec. 
 
Sec. XIV.] OF knowledge and probability. 125 
 
 tion and by the uninterrupted resemblance of their re- 
 lations of succession and contiguity. But it is from 
 this resemblance that the ideas of necessity, of power, 
 and of efificacy are derived. These ideas, therefore, 
 represent not anything that does or can belong to the 
 objects which are constantly conjoined. This is an 
 argument which, in every view we can examine it, 
 will be found perfectly unanswerable. Similar in- 
 stances are still the first source of our idea of power 
 or necessity ; at the same time that they have no influ- 
 ence by their similarity either on each other or on 
 any external object. We must, therefore, turn our- 
 selves to some other quarter to seek the origin of that 
 idea. 
 
 Though the several resembling instances which 
 give rise to the idea of power have no influence on 
 each other, and can never produce any new quality in 
 the object which can be the model of that idea, yet the 
 observation of this resemblance produces a new impres- 
 sion in the mind, which is its real model. For, after 
 we have observed the resemblance in a sufficient 
 number of instances, we immediately feel a determina- 
 tion of the mind to pass from one object to its usual 
 attendant, and to conceive it in a stronger light upon 
 account of that relation. This determination is the 
 only effect of the resemblance ; and therefore must be 
 the same with power or efficacy, whose idea is derived 
 from the resemblance. The several instances of re- 
 sembling conjunctions leads us into the notion of 
 power and necessity. These instances are in them- 
 selves totally distinct from each other, and have no 
 union but in the mind which observes them and col- 
 
126 THE PHILOSOPHY OF HUME. [Part III. 
 
 lects their ideas. Necessity, then, is the effect of this 
 observation, and is nothing but an internal impression 
 of the mind, or a determination to carry our thoughts 
 from one object to another. Without considering it in 
 this view, we can never arrive at the most distant no- 
 tion of it, or be able to attribute it either to external or 
 internal objects, to spirit or body, to causes or effects. 
 
 The necessary connection betwixt causes and effects 
 is the foundation of our inference from one to the 
 other. The foundation of our inference is the transi- 
 tion arising from the accustomed union. These are, 
 therefore, the same. 
 
 The idea of necessity arises from some impression. 
 There is no impression conveyed by our senses which 
 can give rise to that idea. It must, therefore, be de- 
 rived from some internal impression, or impression of 
 reflection. There is no internal impression which has 
 any relation to the present business but that propen- 
 sity which custom produces to pass from an object to 
 the idea of its usual attendant. This, therefore, is the 
 essence of necessity. Upon the whole, necessity is 
 something that exists in the mind, not in objects ; nor 
 is it possible for us ever to form the most distant idea 
 of it, considered as a quality in bodies. Either we 
 have no idea of necessity, or necessity is nothing but 
 that determination of the thought to pass from causes 
 to effects and from effects to causes, according to 
 their experienced union. 
 
 Thus, as the necessity which makes two times two 
 equal to four, or three angles of a triangle equal to two 
 right ones, lies only in the act of the understanding by 
 which we consider and compare these ideas, in like 
 
Sec. XIV.] of knowledge and probability. 127 
 
 manner the necessity or power which unites causes 
 and effects lies in the determination of the mind to 
 pass from the one to the other. The efficacy or 
 energy of causes is neither placed in the causes them- 
 selves, nor in the deity, nor in the concurrence of 
 these two principles ; but belongs entirely to the soul 
 which considers the union of two or more objects in 
 all past instances. It is here that the real power of 
 causes is placed, along with their connection and 
 necessity. 
 
 I am sensible that of all the paradoxes which I 
 have had, or shall hereafter have, occasion to advance 
 in the course of this treatise, the present one is the 
 most violent, and that it is merely by dint of solid 
 proof and reasoning I can ever hope it will have ad- 
 mission, and overcome the inveterate prejudices of 
 mankind. Before we are reconciled to this doctrine, 
 how often must we repeat to ourselves, that the simple 
 view of any two objects or actions, however related, 
 can never give us any idea of power, or of a connec- 
 tion betwixt them ; that this idea arises from the repe- 
 tition of their union ; that the repetition neither dis- 
 covers nor causes anything in the objects, but has an 
 influence only on the mind, by that customary transi- 
 tion it produces ; that this customary transition is, 
 therefore, the same with the power and necessity ; 
 which are consequently qualities of perceptions, not of 
 objects, and are internally felt by the soul, and not 
 perceived externally in bodies ? There is commonly 
 an astonishment attending everything extraordinary ; 
 and this astonishment changes immediately into the 
 highest degree of esteem or contempt, according as we 
 
I2S THE PHILOSOPHY OF HUME. [PART III. 
 
 approve or disapprove of the subject. I am much 
 afraid that though the foregoing reasoning appears 
 to me the shortest and most decisive imaginable, yet 
 with the generality of readers the bias of the mind 
 will prevail, and give them a prejudice against the 
 present doctrine. 
 
 This contrary bias is easily accounted for. It is a 
 common observation that the mind has a great propen- 
 sity to spread itself on external objects, and to conjoin 
 with them any internal impressions which they occa- 
 sion and which always make their appearance at the 
 same time that these objects discover themselves to 
 the senses. Thus, as certain sounds and smells are 
 always found to attend certain visible objects, we nat- 
 urally imagine a conjunction, even in place, betwixt 
 the objects and qualities, though the qualities be of 
 such a nature as to admit of no such conjunction, and 
 really exist nowhere. But of this more fully * hereafter. 
 Meanwhile it is sufficient to observe that the same 
 propensity is the reason why we suppose necessity and 
 power to lie in the objects we consider, not in our 
 mind that considers them, notwithstanding it is not 
 possible for us to form the most distant idea of that 
 quality when it is not taken for the determination of 
 the mind to pass from the idea of an object to that of 
 its usual attendant. 
 
 But, though this be the only reasonable account we 
 can give of necessity, the contrary notion is so riveted 
 in the mind, from the principles above mentioned, that 
 I doubt not but my sentiments will be treated by many 
 as extravagant and ridiculous. What ! the efficacy of 
 
 * Part IV., sec. v. 
 
Sec. XIV.] OF knowledge and prouability. 129 
 
 causes lie in the determination of the mind ! As if 
 causes did not operate entirely independent of the 
 mind, and would not continue their operation even 
 though there was no mind existent to contemplate 
 them or reason concerning them. Thought may well 
 depend on causes for its operation, but not causes on 
 thought. This is to reverse the order of nature, and 
 make that secondary which is really primary. To 
 every operation there is a power proportioned ; and 
 this power must be placed on the body that operates. 
 If we remove the power from one cause, we must 
 ascribe it to another ; but to remove it from all causes 
 and bestow it on a being that is no ways related to the 
 cause or effect but by perceiving them, is a gross ab- 
 surdity, and contrary to the most certain principles of 
 human reason. 
 
 I can only reply to all these arguments that the case 
 is here much the same as if a blind man should pre- 
 tend to find a great many absurdities in the supposi- 
 tion that the color of scarlet is not the same with the 
 sound of a trumpet, nor light the same with solidity. 
 If we have really no idea of a power or efficacy in 
 any object, or of any real connection betwi.xt causes 
 and effects, it will be to little purpose to prove that an 
 efficacy is necessary in all operations. We do not 
 understand our own meaning in talking so, but igno- 
 rantly confound ideas which are entirely distinct from 
 each other. I am, indeed, ready to allow that there 
 may be several qualities, both in material and immate- 
 rial objects, with which we are utterly unacquainted ; 
 and if we please to call these /t^zc^r or efficacy, it will 
 be of little consequence to the world. But, when. 
 
130 THE PHILOSOPHY OF HUME. [PartIU. 
 
 instead of meaning these unknown qualities, we make 
 the terras of power and efficacy signify something of 
 which we have a clear idea and which is incompatible 
 with those objects to which we apply it, obscurity and 
 error begin then to take place, and we are led astray 
 by a false philosophy. This is the case when we trans- 
 fer the determination of the thought to external ob- 
 jects, and suppose any real intelligible connection 
 betwi.xt them ; that being a quality which can only 
 belong to the mind that considers them. 
 
 As to what may be said that the operations of nature 
 are independent of our thought and reasoning, I allow 
 it; and accordingly have observed that objects bear to 
 each other the relations of contiguity and succession, 
 that like objects may be observed in several instances 
 to have like relations, and that all this is independent 
 of, and antecedent to, the operations of the under- 
 standing. But, if we go any farther and ascribe a 
 power or necessary connection to these objects, this 
 is what we can never observe in them, but must draw 
 the idea of it from what we feel internally in contem- 
 plating them. And this I carry so far that I am ready 
 to convert my present reasoning into an instance of 
 it by a subtility which it will not be difficult to com- 
 prehend. 
 
 When any object is presented to us, it immediately 
 conveys to the mind a lively idea of that object which 
 is usually found to attend it ; and this determination 
 of the mind forms the necessary connection of these 
 objects. But when we change the point of view 
 from the objects to the perceptions : in that case the 
 impression is to be considered as the cause, and the 
 
Sec. XIV.] OF knowledge and probability. 131 
 
 lively idea as the effect ; and their necessary connec- 
 tion is that new determination which we feel to pass 
 from the idea of the one to that of the other. The 
 uniting principle among our internal perceptions is as 
 unintelligible as that among external objects, and is 
 not known to us any other way than by experience. 
 Now the nature and effects of experience have been 
 already sufficiently examined and explained. It 
 never gives us any insight into the internal structure 
 or operating principle of objects, but only accustoms 
 the mind to pass from one to another. 
 
 It is now time to collect all the different parts of 
 this reasoning, and by joining them together form an 
 exact definition of the relation of cause and effect, 
 which makes the subject of the present inquiry. This 
 order would not have been excusable, of first examin- 
 ing our inference from the relation before we had ex- 
 plained the relation itself, had it been possible to 
 proceed in a different method. But, as the nature of 
 the relation depends so much on that of the inference, 
 we have been obliged to advance in this seemingly 
 preposterous manner, and make use of terms before 
 we were able exactly to define them or fix their 
 meaning. We shall now correct this fault by giving 
 a precise definition of cause and effect. 
 
 There may two definitions be given of this relation, 
 which are only different by their presenting a differ- 
 ent view of the same object, and making us consider 
 it either as a philosophics.i or as a natural relation ; 
 either as a comparison of two ideas, or as an associa- 
 tion betwixt them. We may define a cause to be 
 ' An object precedent and contiguous to another, and 
 
132 THE PHILOSOPHY OF HUME. [PART III. 
 
 where all the objects resembling the former are placed 
 in like relations of precedency and contiguity to those 
 objects that resemble the latter.' If this definition 
 be esteemed defective because drawn from objects 
 foreign to the cause, we may substitute this other 
 definition in its place, viz., 'A cause is an object pre- 
 cedent and contiguous to another, and so united with 
 it that the idea of the one determines the mind to 
 form the idea of the other, and the impression of the 
 one to form a more lively idea of the other.' Should 
 this definition also be rejected for the same reason, I 
 know no other remedy than that the persons who 
 express this delicacy should substitute a juster defi- 
 nition in its place. But for my part I must own my 
 incapacity for such an undertaking. When I examine 
 with the utmost accuracy those objects which are 
 commonly denominated causes and effects, I find, in 
 considering a single instance, that the one object is 
 precedent and contiguous to the other ; and, in enlarg- 
 ing my view to consider several instances, I find only 
 that like objects are constantly placed in like rela- 
 tions of succession and contiguity. Again, when I 
 consider the influence of this constant conjuction, I 
 perceive that such a relation can never be an object 
 of reasoning, and can never operate upon the mind, 
 but by means of custom, which determines the imag- 
 ination to make a transition from the idea of one 
 object to that of its usual attendant, and from the im- 
 pression of one to a more lively idea of the other. 
 However extraordinary these sentiments may appear, 
 I think it fruitless to trouble myself with any farther 
 
Sec. XIV.] or knowledge and probability, 133 
 
 inquiry or reasoning upon the subject, but shall repose 
 myself on them as on established maxims. 
 
 It will only be proper, before we leave this subject, 
 to draw some corollaries from it, by which we may 
 remove several prejudices and popular errors that 
 have very much prevailed in philosophy. First, We 
 may learn from the foregoing doctrine that all causes 
 are of the same kind, and that in particular there is 
 no foundation for that distinction which we some- 
 times make betwixt efificient causes and causes siite 
 qua non ; or betwixt efificient causes and formal, and 
 material, and exemplary, and final causes. For, as 
 our idea of efficiency is derived from the constant 
 conjunction of two objects, wherever this is observed, 
 the cause is efificient ; and where it is not, there can 
 never be a cause of any kind. For the same reason 
 we must reject the distinction between cause and 
 occasion, when supposed to signify anything essen- 
 tially different from each other. If constant con- 
 junction be implied in what we call occasion, it is a 
 real cause. If not, it is no relation at all, and cannot 
 give rise to any argument or reasoning. 
 
 Secondly, The same course of reasoning will make 
 us conclude that there is but one kind of necessity, as 
 tliere is but one kind of cause, and that the common 
 distinction betwixt moral and physical necessity is 
 without any foundation in nature. This clearl^j ap- 
 pears from the precedent explication of necessity. 
 It is the constant conjunction of objects, along with 
 the determination of the mind, which constitutes a 
 physical necessity : and the removal of these is the 
 same thing with chance. As objects must either be 
 
134 THE PHILOSOPHY OF HUME. [Part III. 
 
 conjoined or not, and as the mind must either be 
 determined or not to pass from one object to another, 
 it is impossible to admit of any medium betwixt 
 chance and an absolute necessity. In weakening this 
 conjunction and determination you do not change the 
 nature of the necessity ; since even in the operation 
 of bodies these have different degrees of constancy 
 and force without producing a different species of 
 that relation. 
 
 The distinction which we often make betwixt 
 power and the exercise of it is equally without foun- 
 dation. 
 
 Thirdly, We may now be able fully to overcome 
 all that repugnance which it is so natural for us to 
 entertain against the foregoing reasoning, by which 
 we endeavored to prove that the necessity of a cause 
 to every beginning of existence i^ not founded on any 
 arguments either demonstrative or intuitive. Such an 
 opinion will not appear strange after the foregoing 
 definitions. If we define a cause to be An object pre- 
 cedent and contiguous to another, and where all the objects 
 resembling the former are placed in a like relation of 
 priority and contiguity to those objects that resemble the 
 latter, we may easily conceive that there is no abso- 
 lute nor metaphysical necessity that every beginning 
 of existence should be attended with such an object. 
 If we define a cause to be An object precedent and con- 
 tiguous to another, and so united with it in the imagina- 
 tion that the idea of the one determines the mind to form 
 
 the id'^Kf-'the-other, and the ijnpression of the one to 
 fortn a more lively idea: of the other, we shall make 
 still less difficulty of assenting to this opinion. Such 
 
Sec. XV.] OF Knowledge and progabilitv. 133 
 
 an influence on the mind is in itself perfectly extra- 
 ordinary and incomprehensible ; nor can we be certain 
 of its reality, but from experience and observation. 
 
 I shall add as a fourth corollary that we can never 
 have reason to believe that any object exists of which 
 we cannot form an idea. For, as all our reasonings 
 concerning existence are derived from causation, and 
 as all our reasonings concerning causation are de- 
 rived from the experienced conjunction of objects, 
 not from any reasoning or reflection, the same expe- 
 rience must give us a notion of these objects, and 
 must remove all mystery from our conclusions. This 
 is so evident that it would scarce have merited our 
 attention, were it not to obviate certain objections of 
 this kind which might arise against the following 
 reasonings concerning matter and substance. I need 
 not observe that a full knowledge of the object is not 
 requisite, but only of "those qualities of it which we 
 believe to exist. 
 
 SECTION XV. 
 Rules by which to judge of causes and effects. 
 
 According to the precedent doctrine, there are no 
 objects which by the mere survey, without consulting 
 experience, we can determine to be the causes of any 
 other ; and no objects which we can certainly de- 
 termine in the same manner not_toJ^^^K^|^Bses. 
 Anything may produce anythi^^lR^^^ri, annihila- 
 tion, motion, reason, volition : all these may arise 
 
136 THE PHILOSOPHY OF HUME. [PART III. 
 
 from one another, or from any other object we can 
 imagine. Nor will this appear strange if we compare 
 two principles explained above, that the co?istant con- 
 junction of objects determines their causation, and * that, 
 properly speaking, no objects are contrary to each other 
 but existence and non-existence. Where objects are not 
 contrary, nothing hinders them from having that con- 
 stant conjunction on which the relation of cause and 
 effect totally depends. 
 
 Since therefore it is possible for all objects to be- 
 come causes or effects to each other, it may be proper 
 to fix some general rules by which we may know 
 when they really are so. 
 
 1. The cause and effect must be contiguous in 
 space and time. 
 
 2. The cause must be prior to the effect. 
 
 3. There must be a constant union betwixt the 
 cause and effect. It is chiefly this quality that con- 
 stitutes the relation. 
 
 4. The same cause always produces the same effect, 
 and the same effect never arises but from the same 
 cause. This principle we derive from experience, and 
 is the source of most of our philosophical reasonings. 
 For when by any clear experiment we have discovered 
 the causes or effects of any phenomenon, we imme- 
 diately extend our observation to every phenomenon 
 of the same kind, without waiting for that constant 
 repetition from which the first idea of this relation 
 is derived. 
 
 5. There is another principle, which hangs upon 
 
 * Part I., sec. V. 
 
Sec. XV.] OF KNOWLEDGE AND PROCABILITV. 137 
 
 this, viz., that, where several different objects produce 
 the same effect, it must be by means of some quality 
 which we discover to be common amongst them. For, 
 as like effects imply like causes, we must always 
 ascribe the causation to the circumstance wherein 
 we discover the resemblance. 
 
 6. The following principle is founded on the same 
 reason. The difference in the effects of two resem- 
 bling objects must proceed from that particular in 
 which they differ. For, as like causes alway produce 
 like effects, when in any instance we find our expecta- 
 tion to be disappointed, we must conclude that this 
 irregularity proceeds from some difference in the 
 causes. 
 
 7. When any object increases or diminishes with 
 the increase or diminution of its cause, it is to be 
 regarded as a compounded effect, derived from the 
 union of the several different effects which arise from 
 the several different parts of the cause. The absence 
 or presence of one part of the cause is here supposed 
 to be always attended with the absence or presence 
 of a proportionable part of the effect. This constant 
 conjunction sufficiently proves that the one part is 
 the cause of the other. We must, however, beware 
 not to draw such a conclusion from a few experiments. 
 A certain degree of heat gives pleasure ; if you dimin- 
 ish that heat, the pleasure diminishes ; but it does 
 not follow that if you augment it beyond a certain 
 degree, the pleasure will likewise augment ; for we 
 find that it degenerates into pain. 
 
 8. The eighth and last rule I shall take notice of 
 is that an object which exists for any time in its 
 
138 The philosophy of hume. [Book It. 
 
 full perfection without any effect is not the sole 
 cause of that effect, but requires to be assisted by 
 some other principle which may forward its influence 
 and operation. For, as like effects necessarily follow 
 from like causes and in a contiguous time and place, 
 their separation for a moment shows that these causes 
 are not complete ones. 
 
 Of liberty and necessity. 
 (From Book II., Part III., Sees. I., II.) 
 
 We come now to explain the direct passions, or the 
 impressions which arise immediately from good or 
 evil, from pain or pleasure. Of this kind are desire 
 and aversion, grief and joy, hope and fear. 
 
 If objects had not an uniform and regular conjunc- 
 tion with each other, we should never arrive at any 
 idea of cause and effect ; and, even after all, the 
 necessity which enters into that idea is nothing but 
 a determination of the mind to pass from one object 
 to its usual attendant and infer the existence of one 
 from that of the other. Here then are two particu- 
 lars which we are to consider as essential to neces- 
 sity, viz., the constant union, and the inference of the 
 mind ; and wherever we discover these we must 
 acknowledge a necessity. As the actions of matter 
 have no necessity but what is derived from these 
 circumstances, and it is not by any insight into the 
 essence of bodies we discover their connection, the 
 absence of this insight, wliile the union and inference 
 
Book II.] OF KNOWi.EnGF, AND PROBABILITY. 139 
 
 remain, will never, in any case, remove the necessity. 
 It is the observation of the union which produces the 
 inference ; for which reason it might be thought suffi- 
 cient if we prove a constant union in the actions of 
 the mind, in order to establish the inference along 
 with the necessity of these actions. But that I may 
 bestow a greater force on my reasoning, I shall ex- 
 amine these particulars apart, and shall first prove 
 from experience that our actions have a constant 
 union with our motives, tempers, and circumstances, 
 before I consider the inferences we draw from it. 
 
 To this end a very slight and general view of the 
 common course of human affairs will be sufficient. 
 There is no light in which we can take them that 
 does not confirm this principle. Whether we consider 
 mankind according to the difference of sexes, ages, 
 governments, conditions, or methods of education, 
 the same uniformity and regular operation of natural 
 principles are discernible. Like causes still produce 
 like effects, in the same manner as in the mutual 
 action of the elements and powers of nature. Are 
 the products of Guienne and of Champagne more 
 regularly different than the sentiments, actions, and 
 passions of the two sexes? Are the changes of our 
 body from infancy to old age more regular and cer- 
 tain than those of our mind and conduct? There is 
 a general course of nature in human actions, as well 
 as in the operations of the sun and the climate. 
 There are also characters peculiar to different nations 
 and particular persons, as well as common to man- 
 kind. The knowledge of these characters is founded 
 on the observatio' of an uniformity in the actions 
 
140 I'HE PHILOSOPHY OP HUME. [BoOK II. 
 
 that flow from them ; and this uniformity forms the 
 very essence of necessity. 
 
 Now some may perhaps find a pretext to deny this 
 regular union and connection. For what is more 
 capricious than human actions ? What more incon- 
 stant than the desires of man ? 
 
 To this I reply that in judging of the actions of 
 men we must proceed upon the same maxims as 
 when we reason concerning external objects. No 
 union can be more constant and certain than that of 
 some actions with some motives and characters ; and, 
 if in other cases the union is uncertain, it is no more 
 than what happens in the operations of body, nor can 
 we conclude anything from the one irregularity, which 
 will not follow equally from the other. 
 
 As the union betwixt motives and actions has the 
 same constancy as that in any natural operations, so 
 its influence on the understanding is also the same 
 in determining us to infer the existence of one from 
 that of another. Moral evidence is nothing but a con- 
 clusion concerning the actions of men derived from 
 the consideration of their motives, temper, and situa- 
 tion. A prince who imposes a tax upon his subjects 
 expects their compliance. A general who conducts 
 an army makes account of a certain degree of cour- 
 age. A merchant looks for fidelity and skill in his 
 factor or supercargo. A man who gives orders for 
 his dinner doubts not of the obedience of his ser- 
 vants. Now I assert that whoever reasons after this 
 manner does ipso facto believe the actions of the will 
 to arise from necessity, and that he knows not what 
 he means when he denies it. 
 
BuoK II.] OF KN<)\VLEDG£ AN13 PR0l)Al3lLlTY. 14I 
 
 All those objects, of which we call the one cause 
 and the other effect, considered in themselves, are as 
 distinct and separate from each other as any two 
 things in nature, nor can we ever, by the most accu- 
 rate survey of them, infer the existence of the one 
 from that of the other. It is only from experience 
 and the observation of their constant union that we 
 are able to form this inference ; and, even after all, 
 the inference is nothing but the effects of custom on 
 the imagination. We must not here be content with 
 saying that the idea of cause and effect arises from 
 objects constantly united ; but must affirm that it is 
 the very same with the idea of these objects, and that 
 the necessary connection is not discovered by a conclu- 
 sion of the understanding, but is merely a perception 
 of the mind. Wherever, therefore, we observe the 
 same union, and wherever the union operates in the 
 same manner upon the belief and opinion, we have 
 the idea of causes and necessity, though perhaps we 
 may avoid those expressions. Motion in one body, 
 in all past instances that have fallen under our 
 observation, is followed upon impulse by motion in 
 another. It is impossible for the mind to penetrate 
 farther. From this constant union it forms the idea 
 of cause and effect, and by its influence feels the 
 necessity. As there is the same constancy and the 
 same influence in what we call moral evidence, I ask 
 no more. What remains can only be a dispute of 
 words. 
 
 The necessity of any action, whether of matter or 
 of the mind, is not properly a quality in the agent, 
 but in any thinking or intelligent being who may 
 
142 THE PHILOSOPHY OF HUME. [Book It. 
 
 consider the action, and consists in the determination 
 of his thought to infer its existence from some pre- 
 ceding objects. We can never free ourselves from the 
 bonds of necessitj'. We may imagine we feel a lib- 
 erty within ourselves ; but a spectator can commonly 
 infer our actions from our motives and character ; 
 and, even where he cannot, he concludes in general 
 that he might, were he perfectly acquainted with 
 every circumstance of our situation and temper and 
 the most secret springs of our complexion and dispo- 
 sition. Now this is the very essence of necessity, 
 according to the foregoing doctrine. 
 
PART IV. 
 
 OF THE SCEPTICAL AND OTHER SYSTEMS OF 
 PHILOSOPHY. 
 
 SECTION I. 
 
 Of scepticism with regard to reason. 
 
 In all demonstrative sciences the rules are certain 
 and infallible ; but when we apply them our fallible 
 and uncertain faculties are very apt to depart from 
 them and fall into error. We must, therefore, in 
 every reasoning form a new judgment as a check or 
 control on our first judgment or belief ; and must 
 enlarge our view to comprehend a Ijind of history of 
 all the instances wherein our understanding has de- 
 ceived us, compared with those wherein its testimony 
 was just and true. Our reason must be considered as 
 a kind of cause, of which truth is the natural. effect ; 
 but such a one as by the irruption of other causes, 
 and by the inconstancy of our mental powers, may 
 frequently be prevented. By this means all knowl- 
 edge degenerates into probability ; and this proba- 
 bility is greater or less, according to our experience 
 of the veracity or deceitfulness of our understanding, 
 
 143 
 
144 THE PHILOSOPHY OF HUME. [PART IV. 
 
 and according to the simplicity or intricacy of the 
 question. 
 
 There is no algebraist nor mathematician so expert 
 in his science as to place entire confidence in any 
 truth immediately upon his discovery of it, or regard 
 it as anything but a mere probability. Every time 
 he runs over his proofs his confidence increases ; but 
 still more by the approbation of his friends ; and is 
 raised to its utmost perfection by the universal asseni 
 and applauses of the learned vi^orld. Now it is evi- 
 dent that this gradual increase of assurance is 
 nothing but the addition of new probabilities, and is 
 derived from the constant union of causes and effects, 
 according to past experience and observation. 
 
 In accounts of any length or importance, merchants 
 seldom trust to the infallible certainty of numbers for 
 their security, but, by the artificial structure of the 
 accounts, produce a probability beyond vv'hat is de- 
 rived from the skill and experience of the account- 
 ant. For that is plainly of itself some degree of 
 probability ; though uncertain and variable, accord- 
 ing to the degrees of his experience and length of the 
 account. Now, as none will maintain that our assur- 
 ance in a long numeration exceeds probability, I may 
 safely affirm that there scarce is any proposition con- 
 cerning numbers of which we can have a fuller secu- 
 rity. For it is easily possible, by gradually diminishing 
 the numbers, to reduce the longest series of addition 
 to the most simple question which can be formed, to 
 an addition of two single numbers. If any single addi- 
 tion were certain, every one would be so, and conse- 
 (juently the whole or total sum. 
 
Sec. I.] or the sceptical PHiLOsorHV. 145 
 
 Since, therefore, all knowledge resolves itself into 
 probability, and becomes at last of the same nature 
 with that evidence which we employ in common life, 
 we must now examine this latter species of reasoning, 
 and see on what foundation it stands. 
 
 In every judgment which we can form concerning 
 probability as well as concerning knowledge, we ought 
 always to correct the first judgment, derived from the 
 nature of the object, by another judgment, derived 
 from the nature of the understanding. Even the man 
 of the best sense and longest experience must be con- 
 scious of many errors in the past, and must still dread 
 the like for the future. Here then arises a new spe- 
 cies of probability to correct and regulate the first, and 
 fix its just standard and proportion. 
 
 Having adjusted these two together, we are obliged 
 by our reason to add a new doubt derived from the 
 possibility of error in the estimation we make of the 
 truth and fidelity of our faculties. This is a doubt 
 which immediately occurs to us, and of which, if we 
 would closely pursue our reason, we cannot avoid giv- 
 ing a decision. But this decision, though it should be 
 favorable to our preceding judgment, being founded 
 only on probability, must weaken still further our first 
 evidence, and must itself be weakened by a fourth 
 doubt of the same kind, and so on in iiiji/iifum j till at 
 last there remain nothing of the original probability, 
 however great we may suppose it to have been, and 
 however small the diminution by every new uncer- 
 tainty. All the rules of logic require a continual dim- 
 inution, and at last a total extinction, of belief and 
 evidence. 
 
146 THE PHILOSOPHY OF HUME. [PauT IV. 
 
 Should it here be asked me whether I sincerely as- 
 sent to this argument which I seem to take such pains 
 to inculcate, and whether I be really one of those 
 sceptics who hold that all is uncertain and that our 
 judgment is not in any thing possessed of any meas- 
 ures of truth and falsehood ; I should reply that this 
 question is entirely superfluous, and that neither I nor 
 any other person was ever sincerely and constantly of 
 that opinion. Nature, by an absolute and uncontrol- 
 lable necessity, has determined us to judge as well as to 
 breathe and feel. My intention, then, in displaying so 
 carefully the arguments of that fantastic sect is only 
 to make the reader sensible of the truth of my hypoth- 
 esis that all our reasonings concerning causes and effects 
 are derived from nothing but custom, and that belief is 
 more properly an act of the sensitive than of the cogita- 
 tive part of our natures. If belief, therefore, were a 
 simple act of the thought, without any peculiar man- 
 ner of conception or the addition of a force and vi- 
 vacity, it must infallibly destroy itself, and in every 
 case terminate in a total suspense of judgment. But, 
 as experience will sufficiently con\ince any one who 
 thinks it worth while to try that though he can find 
 no error in the foregoing arguments, yet he still con- 
 tinues to believe and think and reason as usual, he 
 may safely conclude that his reasoning and belief is 
 some sensation or peculiar manner of conception, 
 which it is impossible for mere ideas and reflections 
 to destroy. 
 
 It is therefore demanded how it happens that even 
 after all we retain a degree of belief n'hich is sufficient 
 for our purpose either in philosophy or common lifef 
 
Sec. II.] OF THK SCEPriCAL PHILOSOPHY. I47 
 
 I answer that after the first and second decision, 
 as the action of the mind becomes forced and unnat- 
 ural and the ideas faint and obscure, though the 
 principles of judgment and the balancing of opposite 
 causes be the same as at the very beginning, yet their 
 influence on the imagination and the vigor they add 
 to or diminish from the thought is by no means equal. 
 
 No wonder, then, the conviction which arises from 
 a subtile reasoning diminishes in proportion to the 
 efforts which the imagination makes to enter into the 
 reasoning and to conceive it in all its parts. Belief, 
 being a lively conception, can never be entire where 
 it is not founded on something natural and easy. 
 
 SECTION II. 
 Of scepticism with regard to the senses. 
 
 Thus the sceptic still continues to reason and be- 
 lieve, even though he asserts that he cannot defend 
 his reason by reason ; and by the same rule he must 
 assent to the principle concerning the existence of 
 body, though he cannot pretend by any arguments of 
 philosophy to maintain its veracity. We may well 
 ask, What causes induce us to believe in the existence of 
 body? but it is in vain to ask. Whether there be body 
 or not? That is a point which we must take for 
 granted in all our reasonings. 
 
 The subject, then, of our present enquiry is con- 
 cerning the causes which induce us to believe in the 
 existence of body. 
 
 We ought to ejfamine apart those two questions 
 
148 THE PHILOSOPHY OF HUME. [PART IV. 
 
 which are commonly confounded together, viz., Why 
 we attribute a continued existence to objects even 
 when they are not present to the senses, and Why we 
 suppose them to have an existence distinct from 
 the mind and perception. Under this last head I 
 comprehend their situation as well as relations, their 
 external position as well as the independence of their 
 existence and operation. These two questions con- 
 cerning the continued and distinct existence of body 
 are intimately connected together. For, if the objects 
 of our senses continue to exist even when they are 
 not perceived, their existence is of course independ- 
 ent of and distinct from the perception ; and, vice 
 versa, if their existence be independent of the percep- 
 tion and distinct from it, they must continue to exist 
 even though they be not perceived. But though the 
 decision of the one question decides the other ; yet, 
 that we may the more easily discover the principles 
 of human nature from whence the decision arises, we 
 shall carry along with us this distinction, and shall 
 consider whether it be the senses, reason, or the imagi- 
 nation that produces the opinion of a continued or of a 
 distinct existence. These are the only questions that 
 are intelligible on the present subject. For, as to the 
 notion of external existence, when taken for some- 
 thing specifically different from our perceptions,* we 
 have already shown its absurdity. 
 
 To begin with the senses, it is evident these facul- 
 ties are incapable of giving rise to the notion of the 
 continued existence of their objects after they no 
 
 * Part 11., sec. VI, 
 
Sec. II.] OF THE SCEPTICAL PHILOSOPHY. I 49 
 
 longer appear to the senses. For that is a contradic- 
 tion in terms, and supposes that the senses continue 
 to operate even after they have ceased all manner of 
 operation. These faculties, therefore, if they have 
 any influence in the present case, must produce the 
 opinion of a distinct, not of a continued, existence ; 
 and, in order to that, must present their impressions 
 either as images and representations, or as these very 
 distinct and external existences. 
 
 That our senses offer not their impressions as the 
 images of something distinct, or independent, and exter- 
 nal, is evident ; because they convey to us nothing 
 but a single perception, and never give us the least 
 intimation of anything beyond. A single perception 
 can never produce the idea of a double existence, 
 but by some inference either of the reason or imagi- 
 nation. When the mind looks farther than what im- 
 mediately appears to it, its conclusions can never be 
 put to the account of the senses ; and it certainly 
 looks farther when from a single perception it infers 
 a double existence, and supposes the relations of re- 
 semblance and causation betwixt them. 
 
 We may also observe that we can attribute a dis- 
 tinct, continued existence to objects without ever 
 consulting reason, or weighing our opinions by any 
 philosophical principles. For philosophy informs us 
 that every thing which appears to the mind is noth- 
 ing but a perception, and is interrupted and de- 
 pendent on the mind ; whereas the vulgar confound 
 perceptions and objects, and attribute a distinct, 
 continued existence to the very things they feel or 
 see. This sentiment, then, as it is entirely unreason- 
 
150 THE PHILOSOPHY OF HUME. [Part IV. 
 
 able, nnist proceed from some other faculty than the 
 understanding. That opinion must be entirely owing 
 to the IMAGINATION : which must now be the subject 
 of our enquiry. 
 
 Since all impressions are internal and perishing ex- 
 istences, and appear as such, the notion of their dis- 
 tinct and continued existence must arise from a con- 
 currence of some of their qualities with the qualities 
 of the imagination ; and since this notion does not 
 extend to all of them, it must arise from certain qual- 
 ities peculiar to some impressions. It will therefore 
 be easy for us to discover these qualities by a com- 
 parison of the impressions to which we attribute a 
 distinct and continued existence with those which we 
 regard as internal and perishing. 
 
 We may observe, then, that it is neither upon ac- 
 count of the involuntariness of certain impressions, as 
 is commonly supposed, nor of their superior force and 
 violence, that we attribute to them a reality and con- 
 tinued existence which w^e refuse to others that are 
 voluntary or feeble. For it is evident our pains and 
 pleasures, our passions and affections, which we never 
 suppose to have any existence be30nd our percep- 
 tion, operate with greater violence and are equally 
 involuntary as the impressions of figure and exten- 
 sion, color and sound, which we suppose to be perma- 
 nent beings. The heat of a fire, when moderate, is 
 supposed to exist in the fire ; but the pain which it 
 causes upon a near approach is not taken to have 
 any being except in the perception. 
 
 These vulgar opinions, then, being rejected, we 
 jnust search for some other hypothesis by which we 
 
;"InC. Il.J Ol' 'I'HE SCKPTlCAt fHtLOSOPHV. Ijt 
 
 may discover those peculiar qualities in our impres- 
 sions which make us attribute to them a distinct and 
 continued existence. 
 
 After a little examination, we shall find that all 
 those objects to which we attribute a continued ex- 
 istence have a peculiar constancy, which distinguishes 
 them from the impressions whose existence depends 
 upon our perception. Those mountains, and houses, 
 and trees which lie at present under my eye have 
 always appeared to me in the same order ; and when 
 I lose sight of them by shutting my eyes or turning 
 my head, I soon after find them return upon me 
 without the least alteration. My bed and table, my 
 books and papers present themselves in the same 
 manner, and change not upon account of any inter- 
 ruption in my seeing or perceiving them. This is the 
 case with all the impressions whose objects are sup- 
 posed to have an external existence ; and is the case 
 with no other impressions, whether gentle or violent, 
 voluntary or involuntary. 
 
 This constancy, however, is not so perfect as not to 
 admit of very considerable exceptions. Bodies often 
 change their position and qualities, and after a little 
 absence or interruption may become hardly knowable. 
 But here it is observable that even in these changes 
 they preserve a coherence, and have a regular depend- 
 ence on each other ; which is the foundation of a 
 kind of reasoning from causation, and produces the 
 opinion of their continued existence. When I return 
 to my chamber after an hour's absence, I find not my 
 fire in the same situation in which I left it : but then 
 I am accustomed in other instances to see a like alter- 
 
152 THE PHILOSOPHY OF MUAIE. [Part 1\'. 
 
 ation produced in a like time, whether I am present 
 or absent, near or remote. This coherence, therefore, 
 in their changes is one of the characteristics of exter- 
 nal objects, as well as their constancy. 
 
 Having found that the opinion of the continued ex- 
 istence of body depends on the coherence and con- 
 stancy of certain impressions, I now proceed to ex- 
 amine after what manner these qualities give rise to 
 so extraordinary an opinion. To begin with the co- 
 herence : we may observe that though these internal 
 impressions which we regard as fleeting and perishing 
 have also a certain coherence or regularity in their 
 appearances, yet it is of somewhat a different nature 
 from that which we discover in bodies. Our passions 
 are found by experience to have a mutual connection 
 with and dependence on each other ; but on no occa- 
 sion is it necessary to suppose that they have existed 
 and operated when they were not perceived, in order 
 to preserve the same dependence and connection of 
 which we have had experience. The case is not the 
 same with relation to external objects. Those require 
 a continued existence, or otherwise lose, in a great 
 measure, the regularity of their operation. Here then 
 I am naturally led to regard the world as something 
 real and durable, and as preserving its existence even 
 vi'hen it is no longer present to my perception. 
 
 But it is evident that, whenever we infer the con- 
 tinued existence of the objects of sense from their co- 
 herence and the frequency of their union, it is in 
 order to bestow on the objects a greater regularity 
 than what is observed in our mere perceptions. 
 The imagination, when set into any train of thinking, 
 
Sec/II.] Of THE SCF.PTICAl, PHlLOSOPHV. 155 
 
 is apt to continue even when its object fails it, and, 
 like a galley put in motion by the oars, carries on its 
 course without any new impulse. Objects have a cer- 
 tain coherence even as they appear to our senses ; but 
 this coherence is much greater and more uniform if 
 we suppose the objects to have a continued existence ; 
 and, as the mind is once in the train of observing an 
 uniformity among objects, it naturally continues till 
 it renders the uniformity as complete as possible. 
 The simple supposition of their continued existence 
 suffices for this purpose, and gives us a notion of a 
 much greater regularity among objects than what 
 they have when we look no farther than our senses. 
 
 But whatever force we may ascribe to this principle, 
 I am afraid it is too weak to support alone so vast an 
 edifice as is that of the continued existence of all ex- 
 ternal bodies, and that we must join the constancy of 
 their appearance to the coherence in order to give a 
 satisfactory account of that opinion. As the explica- 
 tion of this will lead me into a considerable compass 
 of very profound reasoning, I think it proper, in 
 order to avoid confusion, to give a short sketch or 
 abridgment of my system, and afterwards draw out all 
 its parts in their full compass. This inference from 
 the constancy of our perceptions, like the precedent 
 from their coherence, gives rise to the opinion of the 
 continued existence of body, which is prior to that of 
 its distinct existence and produces that latter prin- 
 ciple. 
 
 When we have been accustomed to observe a con- 
 stancy in certain impressions, and have found that 
 the perception of the sun or ocean, for instance, re- 
 
154 I'Me philosophy op hUME. [Part IV. 
 
 turns upon us after an absence or annihilation with 
 like parts and in a like order as at its first appearance, 
 we are not apt to regard these interrupted perceptions 
 as different (which they really are), but on the con- 
 trary consider them as individually the same, upon 
 account of their resemblance. But, as this interrup- 
 tion of their existence is contrary to their perfect 
 identity, and makes us regard the first impression as 
 annihilated and the second as newly created, we find 
 ourselves somewhat at a loss, and are involved in a kind 
 of contradiction. In order to free ourselves from this 
 difficulty, we disguise as much as possible the inter- 
 ruption, or rather remove it entirely, by supposing 
 that these interrupted perceptions are connected by a 
 real existence of which we are insensible. This sup- 
 position, or idea of continued existence, acquires a 
 force and vivacity from the memory of these broken 
 impressions and from that propensity which they 
 give us to suppose them the same ; and, according to 
 the precedent reasoning, the very essence of belief 
 consists in the force and vivacity of the conception. 
 
 In order to justify this system there are four things 
 requisite. First, To explain the pri7icipium individu- 
 ationis, or principle of identity. Secondly, Give a rea- 
 son why the resemblance of our broken and inter- 
 rupted perceptions induces us to attribute an identity 
 to them. Thirdly, Account for that propensity, which 
 this illusion gives, to unite these broken appearances 
 by a continued existence. Fourthly, and lastly. Ex- 
 plain that force and vivacity of conception which 
 arises from the propensity. 
 
 First, As to the principle of individuation ; we can- 
 
Sec. II.] OF THE SCEPTICAL PHILOSOPHY. 155 
 
 not, in any propriety of speech, say that an object 
 is the same with itself, unless we mean that the 
 object existent at one time is the same with itself 
 existent at another. Thus the principle of individu- 
 ation is nothing but the invariable ness and tininter- 
 rupedness of any object through a supposed variation 
 of time, by which the mind can trace it in the differ- 
 ent periods of its existence without any break of the 
 view and without being obliged to form the idea of 
 multiplicity or number. 
 
 I now proceed to explain the second part of my 
 system, and show why the constancy of our percep- 
 tions makes us ascribe to them a perfect numerical 
 identity, though there be very long intervals betwixt 
 their appearance and they have only one of the es- 
 sential qualities of identity, viz., invariable/less. That 
 I may avoid all ambiguity and confusion on this head, 
 I shall observe that I here account for the opinions 
 and belief of the vulgar with regard to the existence 
 ot body ; and therefore must entirely conform myself 
 to their manner of thinking and of expressing them- 
 selves. Now we have already observed that however 
 philosophers may distinguish betwixt the objects and 
 perceptions of the senses — which they suppose coex- 
 istent and resembling — yet this is a distinction which 
 is not comprehended by the generality of mankind, 
 who, as they perceive only one being, can never assent 
 to the opinion of a double existence and representa- 
 tion. Those very sensations which enter by the eye 
 or ear are with them the true objects, nor can they 
 readily conceive that this pen or paper, which is im- 
 mediately perceived, represents another, which is dif- 
 
156 THE PHILOSOPHY OF HUME. [Part IV. 
 
 ferent from, but resembling it. In order therefore 
 to accommodate myself to their notions, I shall at first 
 suppose that there is only a single existence, which 
 I shall call indifferently object ox perception, according 
 as it shall seem best to suit my purpose, understand- 
 ing by both of them what any common man means by 
 a hat, or shoe, or stone, or any other impression con- 
 veyed to him by his senses. I shall be sure to give 
 warning when I return to a more philosophical way of 
 speaking and thinking. 
 
 To enter, therefore, upon the question concerning 
 the source of the error and deception with regard to 
 identity when we attribute it to our resembling per- 
 ceptions notwithstanding their interruption, I must 
 here recall an observation which I have already 
 proved and explained.* Nothing is more apt to make 
 us mistake one idea for another than any relation 
 betwixt them which associates them together in the 
 imagination and makes it pass with facility from one 
 to the other. Of all relations that of resemblance is 
 in this respect the most efficacious ; and that because 
 it not only causes an association of ideas, but also of 
 dispositions, and makes us conceive the one idea by 
 an act or operation of the mind similar to that by 
 which we conceive the other. 
 
 We find by experience that there is such a constancy 
 in almost all the impressions of the senses that their 
 interruption produces no alteration on them, and 
 hinders them not from returning the same in appear- 
 ance and in situation as at their first existence. I 
 
 * Part II. sec. V. 
 
Sec. II.] OF THE SCEPTICAL PHILOSOPHY. 157 
 
 survey the furniture of my chamber ; I shut my eyes, 
 and afterwards open them ; and find the new per- 
 ceptions to resemble perfectly those which formerly 
 struck my senses. This resemblance is observed in a 
 thousand instances, and naturally connects together 
 our ideas of these interrupted perceptions by the 
 strongest relation, and conveys the mind with an easy 
 transition from one to another. An easy transition or 
 passage of the imagination along the ideas of these 
 different and interrupted perceptions is almost the 
 same disposition of mind with that in which we con- 
 sider one constant and uninterrupted perception. It 
 is therefore very natural for us to mistake the one for 
 the other. The thought slides along the succession 
 with equal facility, as if it considered only one object ; 
 and therefore confounds the succession with the 
 identity.* 
 
 But, as the interruption of the appearance seems 
 contrary to the identity, and naturally leads us to re- 
 gard these resembling perceptions as different from 
 each other, we here find ourselves at a loss how to 
 reconcile such opposite opinions. The smooth pas- 
 sage of the imagination along the ideas of the resem- 
 bling perceptions makes us ascribe to them a perfect 
 identity. The interrupted manner of their appearance 
 makes us consider them as so many resembling, but 
 
 * There are two relations, and both of them resemblances, 
 which contribute to our mistaking the succession of our inter- 
 rupted perceptions for an identical object. The first is the re- 
 semblance of the perceptions ; the second is the resemblance 
 which the act of the mind in surveying a succession of resem- 
 bling objects bears to that in surveying an identical object. 
 
158 THE PHILOSOPHY OF HUME. [Part IV. 
 
 Still distinct, beings which appear after certain inter- 
 vals. The perplexity arising from this contradiction 
 produces a propension to unite these broken appear- 
 ances by the fiction of a continued existence; which is 
 the third Tf^xX. of that hypothesis I proposed to explain. 
 
 But as the appearance of a perception in the mind 
 and its existence seem at first sight entirely the same, 
 it may be doubted whether we can ever assent to so 
 palpable a contradiction, and suppose a perception to 
 exist without being present to the mind. 
 
 It is certain that almost all mankind, and even phi- 
 losophers themselves, for the greatest part of their 
 lives, take their perceptions to be their only objects, 
 and suppose that the very being which is intimately 
 present to the mind is the real body or material exist- 
 ence. It is also certain that this very perception or 
 object is supposed to have a continued uninterrupted 
 being, and neither to be annihilated by our absence, 
 nor to be brought into existence by our presence. 
 When we are absent from it, we say it still exists, but 
 that we do not feel, we do not see it. When we are 
 present, we say we feel, or see it. Here thea may 
 arise two questions : First, How we can satisfy our- 
 selves in supposing a perception to be absent from the 
 mind without being annihilated. Secondly, Pd.\.^x\i\\dX 
 manner we conceive an .object to become present to 
 the mind without some new creation of a perception 
 or image ; and what we mean by this seeing, 3C{\d feel- 
 ing, and perceiving. 
 
 As to the first question: We may observe that what 
 we call a mind is nothing but a heap or collection of 
 different perceptions united together by certain rela- 
 
Sec. II.] OF THE SCEPTICAL PHILOSOPHY. 159 
 
 tions, and supposed, though falsely, to be endowed 
 with a perfect simplicity and identity. Now as every 
 perception is distinguishable from another, and may 
 be considered as separately existent, it evidently fol- 
 lows that there is no absurdity in separating any par- 
 ticular perception from the mind ; that is, in breaking 
 off all its relations with that connected mass of per- 
 ceptions which constitute a thinking being. 
 
 The same reasoning affords us an answer to the 
 second question. If the name of perception fenders 
 not this separation from a mind absurd and contra- 
 dictory, the name of object, standing for the very same 
 thing, can never render their conjunction impossible. 
 External objects are seen, and felt, and become pres- 
 ent to the mind ; that is, they acquire such a relation 
 to a connected heap of perceptions as to influence 
 them very considerably in augmenting their number 
 by present reflections and passions, and in storing the 
 memory with ideas. The same continued and unin- 
 terrupted Being may, therefore, be sometimes present 
 to the mind, and sometimes absent from it, without 
 any real or essential change in the Being itself. An 
 interrupted appearance to the senses implies not nec- 
 essarily an interruption in the existence. The suppo- 
 sition of the continued existence of sensible objects or 
 perceptions involves no contradiction. 
 
 But, as we here not only feign but believe this con- 
 tinued existence, the question is, from whence arises 
 such a belief; and this question leads us to the fourth 
 member of this system. It has been proved already 
 that belief in general consists in nothing but the vivac- 
 
l6o THE PHILOSOPHY OF HUME. [Part IV. 
 
 ity of an idea, and that an idea may acquire this 
 vivacity by its relation to some present impression. 
 
 Our memory presents us with a vast number of in- 
 stances of perceptions perfectly resembling each other 
 that return at different distances of time and after 
 considerable interruptions. This resemblance gives 
 us a propension to consider these interrupted percep- 
 tions as the same ; and also a propension to connect 
 them by a continued existence, in order to justify this 
 identity, and avoid the contradiction in which the in- 
 terrupted appearance of these perceptions seems nec- 
 essarily to involve us. Here then we have a propensity 
 to feign the continued existence of all sensible objects ; 
 and, as this propensity arises from some li\-ely impres- 
 sions of the memory, it bestows a vivacity on that 
 fiction ; or, in other words, makes us believe the con- 
 tinued existence of body. 
 
 But, though we are led after this manner, by the 
 natural propensity of the imagination, to ascribe a con- 
 tinued existence to those sensible objects or percep- 
 tions which we find to resemble each other in their 
 interrupted appearance, yet a very little reflection and 
 philosophy is sufficient to make us perceive the fallacy 
 of that opinion. I have already observed that there 
 is an intimate connection betwixt those two princi- 
 ples, of a continued &nA of a distinct or independent ex- 
 istence, and that we no sooner establish the one than 
 the other follows, as a necessary consequence. It is 
 the opinion of a continued existence which first takes 
 place, and without much study or reflection draws the 
 other along with it, wherever the mind follows its first 
 and most natural tendency. But, when we compare 
 
Sec. II.] OF THE SCEPTICAL PHILOSOPHY. l6l 
 
 experiments, and reason a little upon them, we quickly 
 perceive that the doctrine of the independent exist- 
 ence of our sensible perceptions is contrary to the 
 plainest experience. 
 
 When we press one eye with a finger, we immedi- 
 ately perceive all the objects to become double, and 
 one half of them to be removed from their common 
 and natural position. But, as we do not attribute a 
 continued existence to both these perceptions, and as 
 they are both of the same nature, we clearly perceive 
 that all our perceptions are dependent on our organs 
 and the disposition of our nerves and animal spirits. 
 
 The natural consequence of this reasoning should 
 be that our perceptions have no more a continued 
 than an independent existence. The case, however, 
 is otherwise. Philosophers are so far from rejecting 
 the opinion of a continued existence upon rejecting 
 that of the independence and continuance of our sensi- 
 ble perceptions, that, though all sects agree in the latter 
 sentiment, the former, which is, in a manner, its neces- 
 sary consequence, has been peculiar to a few extrava- 
 gant sceptics ; who after all maintained that opinion 
 in words only, and were never able to bring themselves 
 sincerely to believe it. 
 
 There is a great difference betwixt such opinions as 
 we form after a calm and profound reflection, and 
 such as we embrace by a kind of instinct or natural 
 impulse, on account of their suitableness and con- 
 formity to the mind. If these opinions become con- 
 trary, it is not difficult to foresee which of them will 
 have the advantage. As long as our attention is 
 bent upon the subject, the philosophical and studied 
 
l62 -IHE PHILOSOPHY OF HUME. [I'ARr IV. 
 
 principle may prevail ; but the moment we relax our 
 thoughts, nature will display herself and draw us back 
 to our former opinion. Nay, she has sometimes such 
 an influence that she can stop our progress, even in 
 the midst of our most profound reflections and keep 
 us from running on with all the consequences of any 
 philosophical opinion. Thus, though we clearly per- 
 ceive the dependence and interruption of our percep- 
 tions, we stop short in our career, and never upon that 
 account reject the notion of an independent and con- 
 tinued existence. That opinion has taken such a 
 deep root in the imagination that it is impossible ever 
 to eradicate it, nor will any strained metaphysical con- 
 viction of the dependence of our perceptions be suffi- 
 cient for that purpose. 
 
 But, though our natural and obvious principles here 
 prevail above our studied reflections, it is certain there 
 must be some struggle and opposition in the case ; at 
 least so long as these reflections retain any force or 
 vivacity. In order to set ourselves at ease in this 
 particular, we contrive a new hypothesis, which seems 
 to comprehend both these principles of reason and 
 imagination, and distinguish (as we shall do for the 
 future) betwixt perceptions and objects, of which the 
 former are supposed to be interrupted and perishing 
 and difi^erent at every different return ; the latter to 
 be uninterrupted, and to preserve a continued exist- 
 ence and identity. This hypothesis is the philosophi- 
 cal one of the double existence of perceptions and ob- 
 jects ; which pleases our reason, in allowing that our 
 dependent perceptions are interrupted and different ; 
 and at the same time is agreeable to the imagination, 
 
Sec. II.] OF THE SCEPTICAL PHILOSOPHY. 163 
 
 in attributing a continued existence to something else, 
 which we call objects. This philosophical system, there- 
 fore, is the monstrous offspring of two principles which 
 are contrary to each other, which are both at once em- 
 braced by the mind, and which are unable mutually to 
 destroy each other. Not being able to reconcile these 
 two enemies, we endeavor to set ourselves at ease as 
 much as possible, by successively granting to each 
 whatever it demands, and by feigning a double exist- 
 ence, where each may find something that has all the 
 conditions it desires. 
 
 Having thus given an account of all the systems, 
 both popular and philosophical, with regard to ex- 
 ternal existences, I cannot forbear giving vent to a 
 certain sentiment which arises upon reviewing those 
 systems. I begun this subject with premising that 
 we ought to have an implicit faith in our senses, and 
 that this would be the conclusion I should draw from 
 the whole of my reasoning. But to be ingenuous, I 
 feel myself at present of a quite contrary sentiment, 
 and am more inclined to repose no faith at all in my 
 senses, or rather imagination, than to place in it such 
 an implicit confidence. I cannot conceive how such 
 trivial qualities of the fancy, conducted by si^ph false 
 suppositions, can ever lead to any solid and rational 
 system. What then can we look for from this con- 
 fusion of groundless and extraordinary opinions but 
 error and falsehood ? And how can we justify to our- 
 selves any belief we repose in them ? 
 
 This sceptical doubt, both with respect to reason 
 and the senses, is a malady which can never be radi- 
 cally cured, but must return upon us every moment, 
 
164 THE PHILOSOPHY OF HUME. [PART IV. 
 
 however we may chase it away and sometimes may 
 seem entirely free from it. It is impossible upon any 
 system to defend either our understanding or senses ; 
 and we but expose them farther when we endeavor to 
 justify them in that manner. As the sceptical doubt 
 arises naturally from a profound and intense reflection 
 on those subjects, it always increases the farther we 
 carry our reflections, whether in opposition or con- 
 formity to it. Carelessness and inattention alone can 
 afford us any remedy. For this reason I rely entirely 
 upon them ; and take it for granted, whatever may be 
 the reader's opinion at this present moment, that an 
 hour hence he will be persuaded there is both an ex- 
 ternal and internal world. 
 
 SECTION V. 
 
 Of the immateriality of the soul. 
 
 The intellectual world, though involved in infinite 
 obscurities, is not perplexed with any such contradic- 
 tions as those we have discovered in the natural. 
 What is known concerning it agrees with itself ; and 
 what is unknown we must be contented to leave so. 
 
 It is true, would we hearken to certain philosophers, 
 they promise to diminish our ignorance ; but I am 
 afraid it is at the hazard of running us into contra- 
 dictions from which the subject is of itself exempted. 
 These philosophers are the curious reasoners concern- 
 ing the material or immaterial substances in which 
 they suppose our perceptions to inhere. In order to 
 
Sec. v.] of the sceptical philosophy. 165 
 
 put a stop to these endless cavils on both sides, I know 
 no better method than to ask these philosophers in a 
 few words What they mean by substance and inhesion ? 
 And after they have answered this question, it will 
 then be reasonable, and not till then, to enter seriously 
 into the dispute. 
 
 This question we have found impossible to be 
 answered with regard to matter and body ; for it is 
 confessed by the most judicious philosophers that our 
 ideas of bodies are nothing but collections formed by 
 the mind of the ideas of the several distinct sensible 
 qualities of which objects are composed and which 
 we find to have a constant union with each other. In 
 the case of the mind it labors under all the same dif- 
 ficulties. As every idea is derived from a precedent 
 impression, had we any idea of the substance of our 
 minds, we must also have an impression of it ; which 
 is very difficult, if not impossible, to be conceived. 
 For how can an impression represent a substance 
 otherwise than by resembling it ? And how can an 
 impression resemble a substance since, according to 
 this philosophy, it is not a substance, and has none of 
 the peculiar qualities or characteiistics of a substance ? 
 
 But leaving the question of what may or may not be 
 for that other tvhat actually is, I desire those philoso- 
 phers who pretend that we have an idea of the sub- 
 stance of our minds to point out the impression that 
 produces it, and tell distinctly after what manner that 
 impression operates and from what object it is de- 
 rived. Is it an impression of sensation or of reflection ? 
 Is is pleasant, or painful, or indifi'erent ? Does it at- 
 tend us at all times, or does it only return at intervals ? 
 
l66 THE PHILOSOPHY OF HUME. [PART IV. 
 
 If at intervals, at what times principally does it re- 
 turn, and by what causes is it produced ? 
 
 If, instead of answering these questions, any one 
 should evade the difficulty by saying that the defini- 
 tion of a substance is something which may exist by 
 itself, and that this definition ought to satisfy us : 
 should this be said, I should observe that this defini- 
 tion agrees to everything that can possibly be con- 
 ceived, and never will serve to distinguish substance 
 from accident, or the soul from its perceptions. For 
 thus I reason : Whatever is clearly conceived may 
 exist ; and whatever is clearly conceived, after any 
 manner, may exist after the same manner. This is 
 one principle, which has been already acknowledged. 
 Again, everything which is different is distinguish- 
 able, and everything which is distinguishable is sepa- 
 rable by the imagination. This is another principle. 
 My conclusion from both is that, since all our percep- 
 tions are different from each other and from every 
 thing else in the universe, they are also distinct and 
 separable, and may be considered as separately exist- 
 ent, and may exist separately, and have no need of any- 
 thing else to support their existence. They are, there- 
 fore, substances, as far as this definition explains a 
 substance. 
 
 Thus neither by considering the first origin of ideas 
 nor by means of a definition are we able to arrive at 
 any satisfactory notion of substance ; which seems to 
 me a sufficient reason for abandoning utterly that dis- 
 pute concerning the materiality and immateriality 
 of the soul, and makes me absolutely condemn even 
 the question itself. We have no perfect idea of any 
 
Sec. y.l OF THE SCEPTICAL PHtLOSOPHV. 167 
 
 thing but of a perception. A substance is entirely 
 different from a perception. We have, therefore, no 
 idea of a substance. Inhesion in something is supposed 
 to be requisite to support the existence of our percep- 
 tions. Nothing appears requisite to support the exist- 
 ence of a perception. We have, therefore, no idea of 
 inhesion. What possibility then of answering that 
 question Whether perceptions inhere in a material or im- 
 material substance, when we do not so much as under- 
 stand the meaning of the question ? 
 
 From these hypotheses concerning the substance of 
 our perceptions we may pass to another, which is 
 more intelligible, z'/^;., concerning the <ra//j-if of our per- 
 ceptions. Matter and motion, it is commonly said in 
 the schools, however varied, are still matter and mo- 
 tion, and produce only a difference in the position and 
 situation of objects. Divide a body as often as you 
 please, it is still body. Place it in any figure, nothing 
 ever results but figure, or the relation of parts. Move 
 it in any manner, you still find motion or a change of 
 relation. It is absurd to imagine that motion in a 
 circle, for instance, should be nothing but merely mo- 
 tion in a circle ; while motion in another direction, as 
 in an ellipse, should also be a passion or moral reflec- 
 tion : that the shocking of two globular particles 
 should become a sensation of pain, and that the meet- 
 ing of two triangular ones should afford a pleasure. 
 Now as these different shocks and variations and 
 mixtures are the only changes of which matter is sus- 
 ceptible, and as these never afford us any idea of 
 thought or perception, it is concluded to be impos- 
 sible that thought can ever be caused by matter. 
 
l68 THE PHILOSOPHY OF HUME. [Part IV. 
 
 Few have been able to withstand the seeming evi- 
 dence of this argument ; and yet nothing in the world 
 is more easy than to refute it. We need only reflect 
 on what has been proved at large, that we are never 
 sensible of any connection betwixt causes and effects, 
 and that it is only by our experience of their constant 
 conjunction we can arrive at any knowledge of this 
 relation. Now as all objects which are not contrary 
 are susceptible of a constant conjunction, and as no 
 real objects are contrary, * I have inferred from 
 these principles that, to consider the matter a priori, 
 anything may produce anything, and that we shall 
 never discover a reason why any object may or may 
 not be the cause of any other, however great, or how- 
 ever little the resemblance may be betwixt them. 
 This evidently destroys the precedent reasoning con- 
 cerning the cause of thought or perception. For, 
 though there appear no manner of connection betwixt 
 motion or thought, the case is the same with all other 
 causes and effects. 
 
 To pronounce, then, the final decision upon the 
 whole : The question concerning the substance of the 
 soul is absolutely unintelligible ; and, as the constant 
 conjunction of objects constitutes the very essence of 
 cause and effect, matter and motion may often be 
 regarded as the causes of thought, as far as we have 
 any notion of that relation. 
 
 If any one should imagine that the foregoing argu- 
 ments are any ways dangerous to religion, I hope the 
 following apology will remove his apprehensions. 
 
 * Pari III. sec. xv. 
 
Sec. VI.] OF THE SCEPTICAL PHILOSOPHY. 169 
 
 There is no foundation for any conclusion a priori, 
 either concerning the operations, or duration, of any 
 object of which it is possible for the human mind to 
 form a conception. Any object may be imagined to 
 become entirely inactive, or to be annihilated in a 
 moment ; and it is an evident principle, that whatever 
 we can imagine, is possible. Now this is no more true 
 of matter than of spirit ; of an extended compounded 
 substance than of a simple and unextended. In 
 both cases the metaphysical arguments for the im- 
 mortality of the soul are equally inconclusive ; and in 
 both cases the moral arguments and those derived 
 from the analogy of nature are equally strong and 
 convincing. If my philosophy, therefore, makes no 
 addition to the arguments for religion, I have at least 
 the satisfaction to think it takes nothing from them, 
 but that everything remains precisely as before, 
 
 SECTION VI. 
 
 Of personal identity. 
 
 There are some philosophers who imagine we are 
 every moment intimately conscious of what we call 
 our Self ; that we feel its existence and its continu- 
 ance in existence, and are certain, beyond the evi- 
 dence of a demonstration, both of its perfect identity 
 and simplicity. 
 
 For my part, when I enter most intimately into 
 what I call myself, I always stumble on some partic- 
 ular perception or other, of heat or cold, light or 
 
176 THE PHILOSOPHY OF HUME. [Part IV. 
 
 shade, love or hatred, pain or pleasure. I never can 
 catch inyself at any time without a perception, and 
 never can observe anything but the perception. 
 When my perceptions are removed for any time, as 
 by sound sleep, so long am I insensible of myself, 
 and may truly be said not to exist. And were all my 
 perceptions removed by death, and could I neither 
 think, nor feel, nor see, nor love, nor hate after the 
 dissolution of my body, I should be entirely annihi- 
 lated, nor do I conceive what is farther requisite to 
 make me a perfect nonentity. If any one, upon 
 serious and unprejudiced reflection, thinks he has a 
 different notion of himself, I must confess I can 
 reason no longer with him. All I can allow him is 
 that he may be in the right as well as I, and that we 
 are essentially different in this particular. He may, 
 perhaps, perceive something simple and continued, 
 which he calls himself ; though I am certain there is 
 no such principle in me. 
 
 But, setting aside some metaphysicians of this 
 kind, I may venture to affirm of the rest of mankind, 
 that they are nothing but a bundle or collection of 
 different perceptions, which succeed each other with 
 an inconceivable rapidity and are in a perpetual flux 
 and movement. The mind is a kind of theatre, where 
 several perceptions successively make their appear- 
 ance, pass, re-pass, glide away, and mingle in an 
 infinite variety of postures and situations. There is 
 properly no simplicity in it at one time, nor identity in 
 different ; whatever natural propension we may have 
 to imagine that simplicity and identity. The com- 
 parison of the theatre must not mislead us. They 
 
Sec. VI.] OF THE SCEPTICAL PHILOSOPHY. I7I 
 
 are the successive perceptions only, that constitute 
 the mind ; nor have we the most distant notion of the 
 place where these scenes are represented, or of the 
 materials of which it is composed. 
 
 What, then, gives us so great a propension to ascribe 
 an identity to these successive perceptions, and to 
 suppose ourselves possessed of an invariable and un- 
 interrupted existence through the whole course of our 
 lives ? 
 
 We have a distinct idea of an object that remains 
 invariable and uninterrupted through a supposed 
 variation of time ; and this idea we call that of ide7i- 
 tity or sameness. We have also a distinct idea of 
 several different objects existing in succession, and 
 connected together by a close relation ; and this to 
 an accurate view affords as perfect a notion of diver- 
 sity as if there was no manner of relation among the 
 objects. But though these two ideas, of identity and 
 a succession of related objects, be in themselves per- 
 fectly distinct, and even contrary, yet it is certain 
 that in our common way of thinking they are gen- 
 erally confounded with each other. That action of 
 the imagination by which we consider the uninter- 
 rupted and invariable object, and that by which we 
 reflect on the succession of related objects, are almost 
 the same to the feeling, nor is there much more effort 
 of thought required in the latter case than in the 
 former. The relation facilitates the transition of the 
 mind from one object to another, and renders its pas- 
 sage as smooth as if it contemplated one continued 
 object. This resemblance is the cause of the confu- 
 sion and mistake, and makes us substitute the notion 
 
172 THE PHILOSOPHY OF HUME. [Part IV. 
 
 of identity, instead of that of related objects. How- 
 ever at one instant we may consider the related suc- 
 cession as variable or interrupted, we are sure the 
 next to ascribe to it a perfect identity and regard it 
 as invariable and uninterrupted. Our propensity to 
 this mistake is so great from the resemblance above 
 mentioned that we fall into it before we are aware ; 
 and, though we incessantly correct ourselves by re- 
 flection and return to a more accurate method of 
 thinking, yet we cannot long sustain our philosophy, 
 or take off this bias from the imagination. Our last 
 resource is to yield to it and boldly assert that these 
 different related objects are in effect the same, how- 
 ever interrupted and variable. In order to justify to 
 ourselves this absurdity, we often feign some new and 
 unintelligible principle that connects the objects to- 
 gether and prevents their interruption or variation. 
 Thus we feign the continued existence of the percep- 
 tions of our senses, to remove the interruption ; and 
 run into the notion of a soul, and self, and substance, 
 to disguise the variation. It evidently follows that 
 identity is nothing really belonging to these different 
 perceptions and uniting them together, but is merely 
 a quality which we attribute to them because of the 
 union of their ideas in the imagination when we re- 
 flect upon them. 
 
 What I have said concerning the first origin and 
 uncertainty of our notion of identity, as applied to 
 the human mind, may be extended with little or no 
 variation to that of simplicity. An object whose dif- 
 ferent co-existent parts are bound together by a close 
 relation operates upon the imagination after much tlie 
 
Sec. VII.] OF The sceptical philosophy. 173 
 
 same manner as one perfectly simple and indivisible, 
 and requires not a much greater stretch of thought in 
 order to its conception. From this similarity of oper- 
 ation we attribute a simplicity to it, and feign a prin- 
 ciple of union as the support of this simplicity, and 
 the centre of all the different parts and qualities of 
 the object. 
 
 SECTION VII. 
 
 Conclusion of this book. 
 
 I AM first affrighted and confounded with that for- 
 lorn solitude in which I am placed in my philosophy. 
 When I look abroad, I foresee on every side dispute, 
 contradiction, anger, calumny, and detraction. When 
 I turn my eye inward, I find nothing but doubt and 
 ignorance. All the world conspires to oppose and 
 contradict me ; though such is my weakness that I 
 feel all my opinions loosen and fall of themselves 
 when unsupported by the approbation of others. 
 Every step I take is with hesitation, and every new 
 reflection makes me dread an error and absurdity in 
 my reasoning. 
 
 After the most accurate and exact of my reason- 
 ings, I can give no reason why I should assent to it ; 
 and feel nothing but a strong propensity to consider 
 objects strongly in that view under which they appear 
 to me. The memory, senses, and understanding are 
 all of them founded on the imagination, or the vivacity 
 of our ideas. Yet if we assent to every trivial sugges- 
 
174 THE PHIt.OSOPHV OF HUME. [Part IV. 
 
 tion of the fanc)', beside that these suggestions are 
 often contrary to each other, they lead us into such 
 errors, absurdities, and obscurities that we must at last 
 become ashamed of our credulity. 
 
 But, on the other hand, if the consideration of these 
 instances makes us take a resolution to reject all the 
 trivial suggestions of the fancy, and adhere to the un- 
 derstanding, that is, to the general and more estab- 
 lished properties of the imagination ; even this reso- 
 lution, if steadily executed, would be dangerous and 
 attended with the most fatal consequences. For I 
 have already shown * that the understanding, when it 
 acts alone and according to its most general princi- 
 ples, entirely subverts itself and leaves not the lowest 
 degree of evidence in any proposition, either in phi- 
 losophy or common life. 
 
 Most fortunately it happens that since reason is 
 incapable of dispelling these clouds, nature herself 
 suffices to that purpose, and cures nie of this philo- 
 sophical melancholy and delirium, either by relaxing 
 this bent of mind or by some avocation and lively 
 impression of my senses which obliterate all these 
 chimeras. I dine, I play a game of backgammon, I 
 converse, and am merry with my friends ; and when, 
 after three or four hours' amusement, I would return to 
 these speculations, they appear so cold, and strained, 
 and ridiculous, that I cannot find in my heart to enter 
 into them any farther. 
 
 *Sec. I., p. T45. 
 
INDEX. 
 
 Analogy, 28, log. 
 Anthropomorphism, 31, 12S. 
 As-socidtion, 27, 2S, 37, 48, 65, 
 
 107, 131. 
 Autobiography, 13. 
 
 Belief, 27, 28, 29, 45, go, 97, 
 101-105, no, 146, 147, 159, 
 1O3. 
 
 Berkeley, 21 ff., 39, 72. 
 
 Bibliography, i. 
 
 Biography, 4, 13. 
 
 Body, 33, 165. 
 
 Cartesians, 35. 39, 117, 118. 
 Causation, 26-32, 36-42, 66, 
 
 6g, 86-101, log, 131 ff , 167. 
 Causes, kinds of, 133. 
 Certainly, gr. 
 Chance, 107, 133. 
 Clarke, g2. 
 Coherence of impressions, 33, 
 
 153- 
 Confidence in reason, 46. 
 Connection. See Necessary 
 
 connection. 
 Constancy, 33, 34, 153, 156. 
 Constant conjunction, 98, 100, 
 
 log, 124. 
 Contiguity, 27. 2g, 65, 86, 88, 
 
 112, 125, 130. 
 Continuity. 33, 148, 160. 
 Contrariety, 69, 87. 
 
 Demonstration, 32, gr, gg, 
 
 143- 
 Descartes, 35, 55. 
 Determination. 37, 40, 112, 
 
 125-131. 13S. 
 Difference, 70. 
 
 Ding an sich, 38 
 Distinction of reason, 76, 77. 
 
 Efficacy, 113, 114, 116, 121, 
 
 125, I2g. 
 " Enquiry," The, 49 
 Existence, external existence, 
 
 25, 7g, 83, loi, 148, 158, 
 
 163. 
 Experience, 21, g8. 
 Exposition of Hume, 25. 
 E.xtension, 79. See Space. 
 
 Faith, 163. See Scepticism. 
 Fancy. See Imagination. 
 Force, 114, 116. 
 Freedom. See Liberty. 
 
 Green, T. H., 56. 
 
 Habit, 41, 75. 
 Hobbes, g2. 
 Huxley, 56. 
 
 Ideas, 6r, 123; abstract ideas. 
 
 22, 30, 72 ff., 120; innate 
 
 ideas, 29, 118. 
 Identitv, 68, 87, 154, 155,157, 
 
 169 ff. 
 Imagination. 29, 32, 33, 34, 46, 
 
 47, 65, 78, gg, 148, 157, 162, 
 
 169, 171. 173. 
 Impressions, 61, 64, 96, 123, 
 
 126. 
 Immateriality, 35, 164. 
 Independent existence, 33, 34, 
 
 130, 148, 160. 
 Inference, 26 ff., 31, 37, 47, 
 
 90, 97 ff., 126, 131, 13S. 
 Infinite divisibility, 78. 
 
 '75 
 
176 
 
 INDEX. 
 
 Influence of Hume, 54. 
 Instinct, 161. 
 
 Judgment. See Reasoning. 
 
 Kant, 26, 44, 55, 56. 
 Knowledge, 86, 106, 143. 
 
 Liberty and Necessity, 138. 
 Loclie, 21, 30, 40, 55, 93, 114- 
 
 Malebfanche, 115. 
 Materialism, 55, 164. 
 Matter, 22, 117, 135, 165, 167. 
 
 See Substance. 
 Memory, 65, 96, 173. 
 Mind, 34, 40, 45, 60, 158, 170. 
 
 See Soul. 
 Mode, 67, 70. 
 
 Natural realism, 37, 44, 45. 
 
 Natural relations. See Asso- 
 ciation. 
 
 Nature, 43, 130, 174. 
 
 Necessity, necessary connec- 
 tion, 29 ff., 36, 40, 55, 8y, 
 go, 91 ff., 99, 105, I11-135, 
 138, 141, 168. 
 
 Number, 6g, 87. 
 
 Object, 34, 43, 45, 85, 155,- 
 
 159, 162. 
 Occasionalism, 39. 
 
 Perception, 38; perceptions, 
 
 34, 44, 48, 62, 155, 159, 162, 
 
 167, 170. 
 Place. See Space. 
 Possibility, 79, 169. 
 Power, 113, 114, 121, 125, 
 
 127, 129, 134. 
 Principium individuationis, 
 
 154. 
 Piobability, 28, 85, 100, I05, 
 
 106 ff., 143. 
 Production, 89. 
 Proofs, 106. 
 
 Quality, 69, 87. 
 Quantity, 69, 87. 
 
 Reality, 25, 33, 42, 45, 48, 
 
 lOI. 
 
 Reason, reasoning, 29, 32, 33, 
 34, 46, 99, 103, 143, 146, 
 148, 162, 173. 
 
 Reflection, 64. 
 
 Reid, 55. 
 
 Relations, 43, 67; philosophi- 
 cal, 26, 68, 86, loi, 131. 
 
 Resemblance, 27, 66, 68, 87, 
 109, 125, 156. 
 
 Rules for cause and effect, 42, 
 135- 
 
 Scepticism, 36, 46, 55, 143, 
 146, 147, 163, 173. 
 
 Science, 35, 59. 
 
 Self, 35, 169. 
 
 Sensation, 64. 
 
 Senses, 147, 163, 173. 
 
 Simple and complex percep- 
 tions, 62. 
 
 Simplicity of the mind, 172. 
 
 Soul, 33, 34, 35, 164. See 
 Mind. 
 
 Sources of Hume's philoso- 
 phy, 21. 
 
 Space and time, 25, 69, 78, 80, 
 
 87. 
 Spinoza, 55. 
 Substance, 22, 67, 70, 135, 
 
 164 ff., 172. 
 Succession, 29, 8S, 112, 125, 
 
 130. 157- 
 
 "Treatise" and " Enquiry,'' 
 
 49- 
 
 Understanding. See Reason. 
 Uniformity of nature, 29, 48, 
 Unknowable, 38. 
 
 Volition. See Will. 
 
 Will, 30, 31, 42, 43, 119, 138. 
 
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