Essay Concerning Human Understanding

Essay Concerning Human Understanding, a philosophical treatise by Locke, published 1690 (2nd edn, 1694; 4th, 1700; 5th, 1706; all with large additions).

The Essay is an examination of the nature of the human mind and its powers of understanding. Locke begins in Bk I by rejecting the doctrine of ‘innate ideas’, maintaining that all knowledge is based on experience. The objects of understanding are termed by him ideas, and Bk II provides an account of the origin, sorts, and extent of our ideas. The source of ideas is experience, the observation of external objects or of the internal operations of the mind, i.e. sensation or reflection.

In Bk III Locke discusses language. He holds that words have meaning in so far as they stand for ideas in the mind; distinguishing between ‘real’ and ‘nominal’ essence, he argues that terms for natural kinds (e.g. ‘gold’, ‘horse’) can express only nominal essences or sets of ideas.

Bk IV defines knowledge as the perception of the agreement or disagreement of ideas. It is either intuitive and direct, demonstrative (through the interposition of a third idea), or ‘sensitive’, i.e. based upon perception. Knowledge in matters of real existence is limited to two certainties, of our own existence, by intuition, and of the existence of God, by demonstration. We have a lesser degree of certainty of the existence of finite beings without us, for which we must rely on sensitive knowledge. The faculty that God has given us in place of clear knowledge is judgement, whereby the mind takes a proposition to be true or false without demonstration. Locke discusses the relations of faith and reason. Unlike F. Bacon and Hobbes, he holds that faith is nothing but the firm assent of the mind, which should not be accorded to anything except for good reason. Revelation must be judged by reason. But the field of knowledge being so limited, it must be supplemented by faith, and this is the basis of his Reasonableness of Christianity (1695).