Personal Identity

It looks as if I know I am myself, and not just someone who is deluded in thinking he's me like one who thinks he's Napoleon, without any need to look at my body, my brain, or to watch videos of myself, or to ask anybody. I just know I am myself and moreover I know I am the same person who started to write this sentence. Why? One obvious answer is that I remember writing it. In other words, I am linked to the author of that sentence by the appropriate connection: memory. This is Locke's theory of personal identity: to be able to remember subjectively the experiences of one, is to be that one.

Note: for Locke, memory is not merely a criterion of PI, but is constitutive of it.

Some problems

The distinction between

really remembering
seeming to remember (the post-hypnotic suggestion of having done X, or George IV on his deathbed).

Reasonable but wrong reply: "really remembering" = seeming to remember plus having done the thing remembered, i.e., being identical with the person who did X. The hypnotized man did not do X.

Why appealing to PI to make the distinction is circular.

Less plausible but better reply: "really remembering" = seeming to remember plus correct causal link. The hypnotized man's memory doesn't have the appropriate causal link.

Reid's Problem: A is memory-linked to B and B to C; however, A is not memory-linked to C. Hence, although A=B and B=C, it is not true that A=C. This contravenes the transitivity of identity.

Reply: let us add transitivity: if A is memory-linked to B and B to C, then A is identical to C even if A is not (directly) memory-linked to C.

Problem: Does the addition of transitivity excessively weaken the intuitive appeal of the memory theory?

Problem: how reliable is apparent memory in general?

But is the memory theory at all correct? Perhaps, one could argue that memory is just a criterion for PI but does not constitute it. But then, what does PI consist in? In bodily continuity? But if I miraculously changed body, would it not still be me? Just imagine the surprise when you look at "yourself" in the mirror. Does PI consist in what others believe? But everybody could be wrong about me. Imagine some weird scenario of mistaken identity and how upset you would be if others were to misidentify you. Does PI consist in character continuity, keeping the same psychological traits? But one could change suddenly by having a conversion of sort, for example by witnessing something awful and turning from religious to atheist or worse (or viceversa, like St. Paul on the road to Damascus). Perhaps, one might appeal to psychological continuity. Two persons are the same if they are linked by an appropriate psychological connection, much in the same way in which a little acorn and the subsequent majestic oak are the same organism because they are linked by an appropriate plant connection: the acorn developed into the oak. But can this story survive the possibility of hemispheric transplant?

What's going on in the case of Leonard? Is he still the same identical Leonard? He thinks he is; others, Lenny for example, are not so sure. Is he right? If so, why?