wards a teacher of Copley, is at Yale ; one is at Lambeth; the other four are in private hands. An engraving of the Yale picture is given in the collected works, and one from an early picture, which belonged to a descendant, Robert Berkeley, Q.C., in Dublin, is given in Fraser's 'Berkeley.'
Berkeley's widow died at Langley, Kent, 27 May 1786, in her eighty-sixth year. Her daughter Julia, who was an invalid, lived with her and probably survived her. The oldest son Henry died in Ireland. The second, George, took his M. A. degree at Oxford January 1759), and in the same year became vicar of Bray. His wife was Eliza Berkeley [q. v.]
Berkeley's aim throughout his writings is to attack materialism, which Hobbes had openly accepted, and which seemed to lurk under the dualism of the Cartesian schools. His great principle is that esse = percipi : that ' ideas,' in Locke's sense — the immediate objects of the mind in thinking — do not represent something outside the mind, but constitute the whole world of reality, which thus exists in minds alone. In the new theory of vision he prepares the way by arguing that vision represents nothing beyond sensations. Assuming as proved or evident that the sight cannot inform us of distance in a direct line outwards, inasmuch as all the points in such a line are projected upon a single point in the retina, he argues that all sight involves foresight ; that an apparently simple perception involved an infererence founded upon association, and that the visual sensations are merely signs of of corresponding tactual sensations. The connection is 'arbitrary,' like the connection between words and things signified, and sight thus forms a natural language, which we learn to intrepret by experience in terms of touch. This psychological theory has been generally accepted both by Reid and by Hume and their respective followers, and has often been called an almost solitary example of a philosophical discovery. Anticipationns have been noticed in Locke, Descartes, and Malebranche, but the substantial originality of Berkeley remains.
It has been attacked recently by Bailey, Abbot, and Collyns Simon, but still holds its ground, though requiring to be supplemented by later researches. The 'Principles' give the most systematic exposition, and the ; 'Dialogues' the clearest defence of Berkeley's full theory. He explains in the 'Principles' the doctrine reserved in the 'Vision' (Principles. § 44) that the sense of touch is on a level with the sense of sight. The two senses form a reciprocal code of signals, a double language of words significant of each other and intesting because indicating the approach of pains and pleasures. Nor can the intellect infer anything beyond the signs from the signs themselves. This could only be done as Berkeley assumes, by abstraction. He therefore, in the introduction to the 'Principles,' begins by attacking the doctrine of abstract ideas, which, as understood by Locke, implied that we could frame an idea of a triangle neither equilateral, isosceles, nor scalene. Berkeley's 'nominalism' is opposed to this theory. He argues that every idea is individual, though it may represent an indefinite number of other individual ideas, and therefore cannot stand for an entity different from all individual ideas. Abstract ideas are an illusion due to the use of language and a confusion of a symbol calling up a variety of ideas with an independent entity. Matter, therefore, understood as a substratum in which the qualities of things, revealed by sensations, are supposed to inhere, is denounced as a mere metaphysical figment, and Berkeley appeals to common sense to condemn its reality. This rejection of matter and of abstract ideas generally, together with his theory of vision, are noticed by Mill as 'three first-rate philosophical discoveries.' Their influence upon the school represented by Mill is shown in the rejection of materialism by the English empirical school generally, The great difficulty of Berkeley lies in his rather obscure treatment of the theory of time and space. On his showing they seem to be a mere illusion. Consistently with his principles, he rejects the distinction between primary and secondary qualities accepted by Locke, and afterwards revived by Reid on theo common sense theory. All qualities (it may be said) are 'secondary' according to Berkeley. It can be said of no quality more than another that it corresponds (as the primary qualities were supposed to do) to something real in the object independently of the mind. Time, according to Berkeley, is nothing but the succession of ideas in the individual mind. Space or extension goes with abstract ideas, and has no more reality than the secondary qualities of colour, resistance, and other visual and tactual sensations (Principles, §§ 98, 99, &c.) Abstract space means the possibility of movement in the absence of the sensation of resistance (ib. § 116). One corollary from this produced his mathematical controversy. As it is contradictory to speak of unfelt sensations, it is contradictory to speak of sensations less than the minima sensibilia—the atomic ideas of which the sense world is constituted. Hence the mathematical theory of infinitesimals implied contradictions or mysteries, the necessity of which Berkeley advances in justification of theological mysteries. Mill considers that he raised ditficul-
