In God’s Debris by Scott Adams the character named Avatar says that the distinction between a replica of me in the future and someone who is really me in the future, is an illusion. Here is my response:
From a purely objective, third-person point of view, if there really were such a thing, the distinction would be an illusion. But a purely objective, third-person point of view would leave completely out of account what one cares about when one cares about one’s own survival. An objective, third-person account could tell you whether a person at one time is identical to a person at another time for all practical purposes except one: the practical purpose of your own survival. Why not that one also? Because unless you already know, from your own first-person perspective, whether or not you are one of those persons described in the purely objective, third-person account, it won’t matter to you, in terms of your own survival, whether or not the earlier person is identical to the later one. And if you do know, because the description is complete enough for you to recognize yourself as, say, the person at the earlier time according to the description, then the account of how the earlier person and the later one are connected or resemble each other is irrelevant. No matter how convincing, how seemingly practical, the account of the link between the earlier person (you, we are now assuming) and the later one, if in the future you do not know, from your own first-person perspective that you are the person in question, just in the way that you know now which person you are out of all the persons there are; then, for the practical purpose of your survival, either you didn’t survive or that person is someone else.
I discuss this, and other awesome topics!, at greater length in Dreams and Resurrection. If you haven’t bought it yet, what the hell is the matter with you?
Scott Adams, the creator of Dilbert, is well worth following on Twitter, and his book, God’s Debris, is far superior to most attempts at popular philosophy.