Locke’s chief work, An Essay concerning Human Understanding, which had been planned as early as 1670, was published in 1689-90, a short abstract of it having previously appeared in French in Le Clerc’s Bibliotheque Universelle, 1688.  His theoretical works include, further, the two posthumous treatises, On the Conduct of the Understanding (originally intended for incorporation in the fourth edition of the Essay, which, however, appeared in 1700 without this chapter, which probably had proved too extended) and the Elements of Natural Philosophy.  To political and politico-economic questions Locke contributed the two Treatises on Government, 1690, and three essays on money and the coinage.  In the year 1689 appeared the first of three Letters on Tolerance, followed, in 1693, by Some Thoughts on Education, and, in 1695, by The Reasonableness of Christianity as delivered in the Scriptures.  The collected works appeared for the first time in 1714, and in nine volumes in 1853; the philosophical works (edited by St. John) are given in Bonn’s Standard Library (1867-68).[1]

[Footnote 1:  Lord King and Fox Bourne have written on Locke’s life, 1829 and 1876.  A comparison of Locke’s theory of knowledge with Leibnitz’s critique was published by Hartenstein in 1865, and one by Von Benoit (prize dissertation) in 1869, and an exposition of his theory of substance by De Fries in 1879.  Victor Cousin’s Philosophie de Locke has passed through six editions. [Among more recent English discussions reference may be made to Green’s Introduction to Hume’s Treatise on Human Nature, 1874 (new ed. 1890), which is a valuable critique of the line of development, Locke, Berkeley, Hume; Fowler’s Locke, in the English Men of Letters, 1880; and Fraser’s Locke, in Blackwood’s Philosophical Classics, 1890.—­TR.]]

%(a) Theory of Knowledge.%—­Locke’s theory of knowledge is controlled by two tendencies, one native, furnished by the Baconian empiricism, and the other Continental, supplied by the Cartesian question concerning the origin of ideas.  Bacon had demanded the closest connection with experience as the condition of fruitful inquiry.  Locke supports this commendation of experience by a detailed description of the services which it renders to cognition, namely, by showing that, in simple ideas, perception supplies the material for complex ideas, and for all the cognitive work of the understanding.  Descartes had divided ideas, according to their origin, into three classes:  those which are self-formed, those which come from without, and those which are innate (p. 79), and had called this third class the most valuable.  Locke disputes the existence of ideas in the understanding from birth, and makes it receive the elements of knowledge from the senses, that is, from without.  He is a representative of sensationalism,—­not in the stricter sense, first put into the term by