Personal identity and identity

Consider claims like this:

1. What it is for a person x at t₀ to be identical with a person y at t₁>t₀ is for y at t₁ to have a chain of memories leading back to x at t₀ (and maybe: and there is no other competitor).
2. What it is for a person x at t₀ to be identical with a person y at t₁>t₀ is for y at t₁ to have a body that has continuously developed from that of x at t₀ (and maybe: and there is no other competitor).

I think claims of this sort are incredible, not just because of particular entailments or details, but simply because identity is surely ontologically more basic than facts about chains of memories or continuous developments of bodies. Each thing is identical with itself and with nothing else. That is surely more basic to its thinghood than having memories, or having a continuously developing body. Only because x is a thing can it have properties like memories or bodily development. But x is a thing only because it is identical with itself. So to explain x's identity with itself in terms of such properties x has seems absurd.

I think that people who are attracted towards (1), (2) and claims like them don't really think of diachronic personal identity as identity, maybe because they don't think of persons as really entities (or maybe they just don't think of persons as substances).

It might be thought that a stage-theorist need not be worried about this. The stage-theorist, after all, may think that x at t₀ and y at t₁ are different entities, being different stages of a greater whole, and that (1) and (2) give a good account of what makes them be stages of the same whole. But I think this is only somewhat more plausible, because the parthood relation (which the stages stand in to the worm), if there is such a relation, is surely almost as ontologically basic as identity.

This does not mean that the discussion of criteria of personal identity is puerile. For one can take identity to be genuinely primitive, but still look for truths such as:

3. Necessarily, a person x at t₁ has a chain of memories going back to every time prior to t₁ at which this person existed.
4. Necessarily, there are no such chains of memories between distinct persons.

But even if there are such truths (I deny both of these two examples), one will no longer take such truths to be constitutive of identity.