Actually if you are a person that believes c, then it is not ambiguous and does answer the question.Aoi wrote:"At what point does a person become another person?"
I suppose the most clear definition of "person" would be one of the following:
(a) brain (conglomerate of cells)
(b) mind (what the brain does)
(c) soul (in a mind/body independence theory)
(d) personality (traits which describe how you behave)
In (a), (b), and (d), a person never remains in existence but always changes. I don't believe (c) has any credibility and is an obsolete notion, especially in today's time. Anyway, (c) is ambiguous and wouldn't answer the question.
I would also postulate
(e) body (similar to brain, but since you don't usually see your brain on a day to day basis your identity is based on the parts that you can observe)
And I think that if you believe in e that you will have the most difficulty with prosthetic in general and one that change your appearance significantly. Something like a fake tooth is designed to appear as original as possible, but you know that it is fake and it doesn't work quite as well the original - so there is a constant reminder that is it not you.
Even if a prosthetic worked better than the original and you could do new things, there is still the reminder that it is 'not you'
My brother has a repaired ankle. The injury and repair were long enough ago that the scars are practically gone. But he can no longer run and it also changes his walk. He can also tell when a storm is coming. Because of this change in his body, his life is changed every day.
But he also is a believer in c above, and so while he makes allowances for things that have to be done differently, it does not change how he thinks of his identity. And because of his specific beliefs, he is anticipating a new body that will be better than the original one ever was.
So it really seems that identity is subjective. What we really need are two people to talk about each other that know each other very well, but each has a very different definition of identity.
Then we can compare the I of one of them to the You from the other and see where the differences lie.
Older me to Younger me: Get into more fights
Younger me to Older me: Don't move to places (whole long list) where you can't climb trees, ride bikes, take hikes.