Our knowledge under Locke's fourth category of relations— real existence—includes (a) intuitive perceptions of our own existence; (b) demonstrable certainty of the existence of God ; and (c) actual perception of the existence of surrounding things, as long as, but. only as long as the things are present to sense. "If I doubt all other things, that very doubt makes me perceive my own existence" (iv. 9. 3). Faith in the existence of God is vir tually with Locke an expression of faith in the principle of active causality in its ultimate universality. Each person knows that he now exists, and is convinced that he had a beginning; with not less intuitive certainty he knows that "nothing can no more pro duce any real being than it can be equal to two right angles." His final conclusion is that there must be eternally "a most pow erful and most knowing Being, in which, as the origin of all, must be contained all the perfections that can ever after exist," and out of which can come only what it has already in itself ; so that as the cause of my mind, it must be Mind. There is thus causal necessity for Eternal Mind, or what we call "God." But the im manence of God in the universe is a conception foreign to Locke, whose habitual conception was of an extra-mundane deity. For Locke, nearly all that one can affirm or deny about "things ex ternal" is not knowledge but venture or presumptive trust. We have, strictly speaking, no "knowledge" of real beings beyond our own self-conscious existence, the existence of God, and the existence of objects of sense as long as they are actually present to sense. Accordingly, purely rational science of external Nature is, according to Locke, impossible. All our "interpretations of nature" are inadequate; only reasonable probabilities, not final rational certainties.
It was Locke's distinction to present to the modern world, in his own "historical plain method," perhaps the largest assortment ever made by any individual of facts characteristic of human un derstanding. Criticism of the presuppositions implied in those facts—by Kant and his successors, and in Britain more unpre tentiously by Reid, all under the stimulus of Hume's sceptical criticism—has employed philosophers since Locke in the Essay Concerning Human Understanding collected materials that raised deeper philosophical problems than he tried to solve. Locke's
mission was to initiate modern criticism of the foundation and limits of our knowledge. Hume negatively, and the German and Scottish schools constructively, continued what it was Locke's glory to have begun.
BiBuoGRAPHY.—There are numerous editions of Locke's collective works. The Essay Concerning Human Understanding has passed through some 4o editions (including that of A. C. Fraser, 2 vols., Oxford, 1894), besides being often translated and abridged, notably by A. S. Pringle-Pattison (1924). The two treatises On Civil Govern ment were published in Everyman's Library (1924), and The Educa tional Writings were edited by J. W. Adamson (1912 ; 2nd ed., 1922). H. 011ion has published Lettres Inedites de J. Locke a Nicholas Thoynard, Philip van Limborch et Edward Clarke (1912), and B. Rand has edited The Correspondence of Locke and Edward Clarke, with a good biographical study (5927).
Criticism and Commentaries: Leibnitz, Nouveaux Essais sur l'en tendement humain (1765) ; V. Cousin, La phil. de Locke (1829) ; J. Brown, Locke and Sydenham (3rd ed., 1866) ; A. Campbell Fraser, Locke (in "Philos. Classics for Eng. Readers," 1890) ; A. Seth, "Epistemology in Locke and Kant," in Philos. Review (1893) ; C. Bastide, John Locke (Paris, 5907) ; S. Alexander, Locke (1908) ; papers on various aspects of Locke by C. Bacumker in Archiv. fur Gesch. der Philos. (vol. xxxi., 2 pts., 1908-09), in Philos. Jahrb. (vol. xxi.) ; H. 011ion, La phil. generale de Locke (1909) ; J. Seth, English Philosophers (1912) ; E. Krakowskl, Les Sources medievales de la phil. de Locke (5915) ; J. Gibson, Locke's Theory of Knowledge, etc. (1917) ; S. P. Lamprecht, The Moral and Political Philosophy of John Locke (Columbia, W. R. Sorbey, Hist. of Eng. Philosophy (1920) ; full bibliography in tlberweg, Gesch. der Philosophie, vol. iii. (1914) •