Although Elizier has dealt with personal identity questions (in terms of ruling out the body theory), he has not actually, as far as I know, "solved" the problem of Personal Identity as it is understood in philosophy. Nor, as far as I know, has any thinker (Robin Hanson, Yvain, etc) broadly in the same school of thought.
Why do I think it worth solving? One- Lesswrong has a tradition of trying to solve all of philosophy through thinking better than philosophers do. Even when I don't agree with it, the result is often enlightening. Two- What counts as 'same person' could easily have significant implications for large numbers of ethical dilemnas, and thus for Lesswrongian ethics.
Three- most importantly of all, the correct theory has practical implications for cryonics. I don't know enough to assert any theory as actually true, but if, say, Identity as Continuity of Form rather than of Matter were the true theory it would mean that preserving only the mental data would not be enough. What kind of preservation is necessary also varies somewhat- the difference in requirement based on a Continuity of Consciousness v.s a Continuity of Psyche theory, for example should be obvious.
I'm curious what people here think. What is the correct answer? No-self theory? Psyche theory? Derek Parfit's theory in some manner? Or if there is a correct way to dissolve the question, what is that correct way?
I took a stab at dissolving personal identity, and managed to do so to my own satisfaction. Most people seemed to feel like this made progress but did not actually solve the question, however.
Short version of my personal answer: "personal identity" doesn't actually correspond with anything fundamental in the world, but for whatever reason, our brains seem to include planning machinery that's based on subjective expectation ("if I do this, what do I expect to experience as a result?") and which drives our behavior more strongly than abstract reasoning does. Since you can't have subjective expectation without some definition for a "self", our brains always end up having some (implicit or explicit) model for continuity of self that they use for making decisions. But at least in epistemic terms, there doesn't seem to be any reason to assume that one definition would be better than any other. In instrumental terms, some definitions might work better than others, since different conceptions of personal identity will lead to different kinds of actions.
I think an important part of the rationalist's plight is attempting to understand the design intents behind these built-in unapologetic old mechanisms for recognizing ourselves in the world, which any self-preservation machine capable of rationality must surely have. But I don't know if we can ever really understand them, they wern't designed to be understood, in fact they seem to be designed to permit being misunderstood to a disturbing degree. I find that often when I think "I" have won, finally achieved a some sense of self-comprehension suffi... (read more)