Mr. Locke’s own account of our ideas of substance is a good deal spun out, and is enriched with as many illustrations from the qualities of gold, as if he had been candidate for the place of assay-master of the mint. The chapter ‘On Identity’ is perhaps the best reasoned and the most full of thought and observation of any in the Essay: though the author sets out with an observation which seems to augur differently. For after explaining identity as it relates to individuality, or implies that a thing is the same with itself, he says, ‘From what has been said it is easy to discover what is so much inquired after, the _principium individuationis_: and that, it is plain, is existence itself, which determines a being of any sort to a particular time and place, incommunicable to two beings of the same kind.’ He then, very wisely quitting this principle which would certainly be of no use to him, proceeds directly to account for the identity of different things from a continuance, not of the same substance, but of the same essence, or of the characteristic properties of any thing, carried on in succession; as a river is the same while it flows through the same channel, or an oak while it retains the same organization, and a man while he retains the same life and continued consciousness. In the chapter entitled ‘Of true and false Ideas,’ the author supposes truth to depend on some mental or verbal proposition, and does not, like Hobbes and the modern metaphysical writers, make it consist entirely in a form of words. In the last chapter of the first volume he treats of the association of ideas. This chapter was added after the first edition of the work, and he confesses, that the subject was something new to him. He has treated it in that mixed way of observation and reasoning, in which the peculiar force of his mind lay. The account he has given of it does not form a system, but the fragments of a system, something like the French memoirs that are to serve for the materials of a history. He does not appear to have laid down any general theorem on the subject, or to have been aware of the possibility of applying this principle to account in a plausible manner for the whole chain of our thoughts and feelings, as Hobbes and Hartley have done. Sound, practical, good sense, and a kind of discursive observation, neither grovelling in vulgar common place, nor soaring into the regions of paradox, are in fact the general characteristics of his mind, which has not been understood by his admirers and commentators. A short passage will suffice to show his manner of considering this doctrine of association.