  Reid is interested in the notion of memory not only for its own sake but also because of its conceptual connection to the notion of personal identity. Reid criticizes Locke’s theory of personal identity for inferring a metaphysical hypothesis now called the Memory Theory from the conceptual connection between memory and personal identity. On this theory, personal identity consists in memory; sameness of memory is metaphysically necessary and sufficient for sameness of persons. According to Reid, memory is neither necessary nor sufficient for personal identity, metaphysically speaking. Indeed, Reid holds that it is impossible to account for personal identity in any terms other than itself. Personal identity is simple and unanalyzable. Though memory is not the metaphysical ground of personal identity, according to Reid, it provides first-personal evidence of personal identity. I know that I was present at my graduation because I remember being there. Memories do not make one the same person over time. Rather, memories allow one to know one’s own past, immediately and directly.