[Footnote 1: The example of Arthur Collier shows that the same results which Berkeley reaches empirically can be obtained from the standpoint of rationalism. Following Malebranche, and developing further the idealistic tendencies of the latter, Collier had, independently of Berkeley, conceived the doctrine of the "non-existence or impossibility of an external world "; but had not worked it out in his Clavis Universalis, 1713, until after the appearance of Berkeley's chief work, and not without consideration of this. The general point of view and the arguments are the same: Existence is equivalent to being perceived by God; the creation of a real world of matter apart from the ideal world in God and from sensuous perceptions in us would have been a superfluous device, etc.]
[Footnote 2: It should be remembered, however, that this immediate knowledge of ourselves is also "not after the manner of an idea or sensation." Our knowledge of spirits is always mediated by "notions" not by "ideas" in the strict sense, that is, not by "images." Cf. Principles, §§ 27, 135 seq., especially in the second edition.—TR.]
In contrast to the fearlessness with which Berkeley propounds his spiritualism, his anxious endeavors to take away the appearance of paradox from his immaterialistic doctrine, and to show its complete agreement with common sense, excite surprise. Even the common man, he argues, desires nothing more than that his perceptions be real; the distinction between idea and object is an invention of philosophers. Here Berkeley cannot be acquitted of a certain sophistical play upon the term "idea," which, in fact, is ambiguous. He understands by it that which the soul perceives (its immediate, inner object), but the popular mind, that through which the soul perceives an object. The reality of an idea in us is different from the idea of a real thing, or from the reality of that which is perceived without us by means of the idea, and it is just this last meaning which common sense affirms and Berkeley denies. In any case it was a work of great merit to have transferred the existence of objects beyond our ideas, of things-in-themselves, out of the region of the self-evident into the region of the problematical. We never get beyond the circle of our ideas, and if we posit a thing-in-itself as the ground and object of the idea, this also is simply a thought, an idea. For us there is no being except that of the perceiver and the perceived. Later we shall meet two other forms of idealism, in Leibnitz and Fichte. Both of these agree with Berkeley that spiritual beings alone are active, and active beings alone real, and that the being of the inactive consists in their being perceived. But while in Berkeley the objective ideas are impressed upon finite spirits by the Infinite Spirit from without and singly, with Leibnitz they appear as a fullness of germs, which God implanted together in the monads at the beginning, and which the individual develops into consciousness, and with Fichte they become the unconscious productions of the Absolute Ego acting in the individual egos. For the two former as many worlds exist as there are individual spirits, their harmony being guaranteed, in the one case, by the consistency of God's working, and, in the other, by his foresight. For Fichte, on the other hand, there is but one world, for the absolute is not outside the individual spirits, but the uniformly working force within them.
(b) Hume.—David Hume was born in Edinburgh in 1711, and died in the same city, 1776. His position as librarian, which he held in the place of his birth, 1752-57, gave the opportunity for his History of England( 1754-62). His chief work, the Treatise on Human Nature, which, however, found few readers, was composed during his first residence in France in 1734-37. Later he worked over the first book of this work into his Enquiry concerning Human Understanding (1748); the second book into A Dissertation on the Passions; and the third into An Enquiry concerning the Principles of Morals. These, and others of his essays, found so much favor that, during his second sojourn in France, as secretary to Lord Hertford, in 1763-66, he was already honored as a philosopher of world-wide renown. Then, after serving for some time as Under-Secretary of State, he retired to private life at home (1769).
The three books of the Treatise on Human Nature, which appeared in 1739-40, are entitled Of the Understanding, Of the Passions, Of Morals. Of the five volumes of the Essays, the first contains the Essays Moral, Political, and Literary, 1741-42; the second, the Enquiry concerning Human Understanding, 1748; the third, the Enquiry concerning the Principles of Morals, 1751; the fourth, the Political Discourses, 1752; the fifth, 1757, the Four Dissertations, including that On the Passions and the Natural History of Religion. After Hume's death appeared the Autobiography, 1777; the Dialogues concerning Natural Religion, 1779; and the two small essays on Suicide and the Immortality of the Soul, 1783.[1] The Philosophical Works were published in 1827, and frequently afterward.[2]
[Footnote 1: Or 1777, cf. Green and Grose's edition, vol. iii. p. 67 seq.—Tr.]
[Footnote 2: Among the works on Hume we may mention Jodl's prize treatise, 1872, and Huxley's Hume (English Men of Letters), 1879. [The reader may be referred also to Knight's Hume (Blackwood's Philosophical Classics), 1886; to T.H. Green's "Introductions" in Green and Grose's edition of the collected works in four volumes, 1874 (new ed. 1889-90), which is now standard; and to Selby-Bigge's reprint of the original edition of the Treatise, I vol., 1888, with a valuable Analytical Index.]
Hume's object, like that of Berkeley, is the improvement of Locke's doctrine of knowledge. In several respects he does not go so far as Berkeley, in others very much farther. In agreement with Berkeley's ultra-nominalism, which combats even the possibility of abstract ideas, he yet does not follow him to the extent of denying external reality. On the other hand, he carries out more consistently Berkeley's hint that immediate sensation includes less than is ascribed to it (e.g., that by vision we perceive colors only, and not distance, etc.), as well as his principle—destructive to the certainty of our knowledge of nature—that there is no causality among phenomena; and brings the question of substance to, the negative conclusion, that there is no need whatever for a support for groups of qualities, and, therefore, that substantiality is to be denied to immaterial as well as to material beings. The points in Locke's philosophy which seemed to Hume to need completion were different from those at which Berkeley had struck in. The antithesis of rational and empirical knowledge is more sharply conceived; the combination of ideas is not left to the choice of the understanding but placed under the dominion of psychological laws; and to the distinction between outer and inner experience (to the former of which priority is conceded, on the ground that we must have had an external sensation before we can, through reflection, be conscious of it as an internal phenomenon), there is added a second, as important as the other and crossing it, between impressions and ideas, of which the former are likewise made prior to the latter.
Everyone will acknowledge the considerable difference between a sensation actually present (of heat, for instance) and the mere idea of one previously experienced, or shortly to come. This consists in the greater force, liveliness, and vividness of the former. Although these two classes of states (the idea of a landscape described by a poet and the perception of a real one, anger and the thought of anger) are only quantitatively distinct, they are scarcely ever in danger of being confused—the most lively idea is always less so than the weakest perception. The actual, outer or inner, sensations may be termed impressions; the weaker images of memory or imagination, which they leave behind them, ideas. Since nothing can gain entrance to the soul except through the two portals of outer and inner experience, there is no idea which has not arisen from an impression or several such; every idea is the image and copy of an impression. But as the understanding and imagination variously combine, separate, and transpose the elements furnished by the senses and lingering in memory, the possibility of error arises. A hidden, and, therefore more dangerous source of error consists in the reference of an idea to a different impression than the one of which it is the copy. The concepts substance and causality are examples of such false reference.
The combination of ideas takes place without freedom, in a purely mechanical, way according to fixed rules, which in the last analysis reduce to three fundamental laws of association: Ideas are associated (1) according to their resemblance and contrast; (2) according to their contiguity in space and time; (3) according to their causal connection. Mathematics is based on the operation of the first of these laws, on the immediate or mediate knowledge of the resemblance, contrariety, and quantitative relations of ideas; the descriptive and experimental part of the sciences of nature and of man on the second; religion, metaphysics, and that part of physical and moral science which goes beyond mere observation on the third. The theory of knowledge has to determine the boundaries of human understanding and the degree of credibility to which these sciences are entitled.