 Locke ([1689] 1998)—who was perhaps anticipated in this by Spinoza (Lin 2005)—discussed the idea that what makes a person at a given time count as the same person as a person at an earlier time is that he remembers the earlier person’s experiences. This memory theory of personal identity  has been much discussed since Locke (Mathews, Bok, &amp; Rabins 2009), and there are well-known substantive and methodological problems for it. The primary substantive problem is that the memory criterion for personal identity appears to be uninformative, because one can by definition remember only one’s own experiences, not those of anyone else—if memory thus presupposes personal identity, it is unenlightening to say that personal identity presupposes memory. There have been attempts to meet this objection by introducing the notion of quasi-memory, which is meant to be like the notion of memory without the implication of personal identity (Buford 2009; Parfit 1984; Roache 2006; Shoemaker 1970). While the notion of quasi-memory may enable us to disentangle memory from personal identity, it remains to be seen whether it is empirically defensible (Northoff 2000).