The sixth part of Professor Dan Robinson's series on Reid's critique of David Hume. In the third of his Essays on The Intellectual Powers of Man, Reid devotes the fourth chapter to the concept of 'identity', and the sixth chapter to Locke's theory of 'personal identity'. This latter chapter is widely regarded as a definitive refutation of the thesis that personal identity is no more than memories of a certain sort, less a “bundle of perceptions”. As he says, “This conviction of one’s own identity is utterly necessary for all exercise of reason. The operations of reason—whether practical reasoning about what to do or speculative reasoning in the building up of a theory—are made up of successive parts. In any reasoning that I perform, the early parts are the foundation of the later ones, and if I didn’t have the conviction that the early parts are propositions that I have approved or written down, I would have no reason to proceed to the later parts in any theoretical or practical project whatever”.