John Locke asserted that continuity of memory was what defined the me-ness of each of us, our sense of identity. A 1980’s thought experiment by Derek Parfit puts an interesting twist on that and causes us to question whether this common-sense notion is sufficient. post
The first question imagines a simple teleporter:
“Suppose that you enter a cubicle in which, when you press a button, a scanner records the states of all the cells in your brain and body, destroying both while doing so. This information is then transmitted at the speed of light to some other planet, where a replicator produces a perfect organic copy of you. Since the brain of your Replica is exactly like yours, it will seem to remember living your life up to the moment when you pressed the button, its character will be just like yours, and it will be in every other way psychologically continuous with you.”
The question is whether you’d press the button, and as Parfitt observes elsewhere the effect is not terribly different in some ways from waking up from a sleep.
If you manage to press the button, it gets more and more complex from there. We can imagine the machine messes up and doesn’t vaporize you at the source teleporter. The duplicate calls up the authorities and asks to have you vaporized immediately as there’s been a mistake with the teleporter. How do you feel about that? And who is the “you” here anyway?
Parfit draws some conclusions for this that are controversial, and from which some say he has retreated from in recent years. (Link)
The problem is also dealt with on The Big Bang Theory