FierceContinent wrote:nem ok. a person's identity is defined by *a* core personality
There would be no continuity. There would be a recurring pattern of how a person is viewed from the outside and also the other way round.
Ok, whose core personality? Surely just any old core personality won't do. If I put some randomly chosen core personality in Bob's body, do I now have Bob? Or are the chances that I probably have some third person wearing a Bob suit?
You've not offered us anything about a particular personality that makes it Bob's. You're just using an empty term - you may as well say that Bob's personality makes him Bob because it instantiates Bob's soul
, or Bob's essence
. It would be about as meaningful as saying it instantiated his core emotions or what have you. Having said that it instantiates whatever, you can't do anything more than you could a moment ago.
All you're really saying is "Whatever makes Bob himself, well wherever that occurs we'll have Bob."
Which is really just to say "Wherever Bob is: there he is."
But, since you don't know what makes Bob himself, you can't really argue that it's probable that it will reoccur on any finite timeline. You can't even, strictly speaking, say that what makes Bob himself exists entirely in his head – it may well be that Bob would be an entirely different person, if Bob's mind was held more or less constant and he had different environmental conditions around him. Nor can you reject mind-body dualism (or any other theory about reincarnation or the absence thereof) on those grounds.
At the end of the argument, even if the argument evaluates to be logically valid, (i.e. you run through your assumptions and get 'true' out at the other end,) you haven't got any more information out of the argument than you put in. You haven't managed to say anything about the world, you've just described something about how certain terms map onto each other in your head.
I don't want to come off as a massive downer on this though. This is a much more general problem in philosophy: What is it about a thing that makes it THAT thing? It's not specifically a problem with personal identity and philosophers have been arguing the toss out of it for hundreds of years in one form or another. If you want to be able to get any significant information out of the argument at the other end, if you want to be able to say anything about how the world actually is; then you need to solve that problem as well. Personal identity is just a rather tricky thing that conflates the problem of identity (What makes this thing THIS thing) and the problem of personality (what makes a chair a chair, what makes Bob Bob....)
The former of those questions people will often answer by reference to a unique location in time and space. The latter of those questions is still up in the air.
However, it seems to me even if you solve the latter, unless you solve the former in a particular way people could still meaningfully reply that they didn't just want any Bob, (just as they could meaningfully reply, looking at the broken remnants of their chair that they didn't just want any chair) they wanted THEIR Bob. If you solve the problem of personality to be a pattern - then you may well find that the problem of identity still scuppers many of the intuitions that make reincarnation a desirable thing to argue for anyway.
And if it turns out that the question of personality is completed by reference not just to Bob's internal state of mind, but to his external stimuli – or if the question of personality is determined by saying that Bob is a particular part of a greater pattern; part of the history of the world, to which you're making reference – what people mean by 'Bob' may well end up defined in such a way that he couldn't recur even on an infinite time-line. Bob's definition may not actually be a bound set.