Does anybody know?

Often we speak of one's “personal identity” as what makes one the person one is. Your identity in this sense consists roughly of what makes you unique as an individual and different from others. 

- Or it is the way you see or define yourself.

It can also be described as the network of values and convictions that structure your life. 

This individual identity is a property (or set of properties). Presumably it is one you have only contingently, you might have had a different identity from the one you in fact have.

It is also a property that you may have only temporarily. You could swap your current individual identity for a new one, or perhaps even get by without any.

-What is the practical importance of facts about our identity?

-Why should we care about it?

-What matters in identity?

-Why does it matter? 

Imagine that surgeons are going to put your brain into my head and that neither of us has any choice about this. Will the resulting person who will presumably think he is you be responsible for my actions or for yours? (Or both? Or neither?) Suppose he will be in terrible pain after the operation unless one of us pays a large sum in advance. If we were both entirely selfish, which of us would have a reason to pay?

The answer may seem to turn entirely on whether the resulting person would be you or I. Only you can be responsible for your actions. The only one whose future welfare you cannot rationally ignore is yourself. You have a special, selfish interest in your own future and no one else's. Identity itself matters practically. 

But some deny this.