  Reid’s first criticism rests on his interpreting Locke’s definition as committing him to the position that a person is a subject of thought, which Reid regards as implying that a person is a thinking substance. At the same time, Locke appears to be committed to an analysis of personal identity in terms of memory, or, as Locke would put it, consciousness of the past. Reid notes that Locke is aware of some of the consequences of the Memory Theory: if sameness of consciousness or memory is necessary and sufficient for sameness of person, then it is possible for there to be sameness of person without sameness of thinking Being. In other words, it is logically and metaphysically possible for a person to be “transferred from one intelligent being to another,” or for “two or twenty intelligent beings to be the same person” (Essays, 276). Locke’s response to these worries, as well as worries about periods of interrupted consciousness, as in sleep, highlights Reid’s criticism: “…[I]n all these cases…doubts are raised whether we are the same thinking thing; i.e. the same substance or no. Which however reasonable, or unreasonable, concerns not personal Identity at all. The Question being what makes the same Person, and not whether it be the same Identical Substance…” (Locke, Essay, Book II.xxvii.10). Reid’s criticism is not that cases of transfer or fission are incoherent, though he thinks they are. Rather, his criticism is that the possibility of sameness of person without sameness of thinking Being that the Memory Theory allows is inconsistent with Locke’s characterization of a person as a ‘thinking Being’. Given that Reid thinks that this initial characterization is correct, he regards this as a reductio of the Memory Theory.