This is a well known paradox in the philosophy of mind and has been used as an objection against the materialist thesis (that everything that makes up the human mind is physical). The year is 2500, and teleportation technology has been perfected for use on humans in interstellar travels. This is how the human teleporter works: instead of actually sending you (with all of your atoms) through space-time, it simply scans your body, capturing all the information on every subatomic particle in your body at an instant (assume that they got around Heisenberg's uncertainty principle), at which point your body is destroyed (don't worry, you are put under anaesthetic for the procedure), while the information of those atoms gets transmitted to the destination, where a machine will synthesise an exact replica of you (exactly the same down to the subatomic level) using new atoms. You then wake up in a different galaxy (after the anaesthetics wear off - and the anaesthetics would also be 'teleported' by the way), with all your memory before the teleportation intact, convinced that you have survived the procedure. Of course the atoms are all new, but isn't the new body still the same 'you'? (In real life, every atom in our body eventually gets replaced anyway.) Now let's add a twist. Instead of destroying your original body, it is preserved during the scanning process. So now we have TWO copies of you: the original one, and the replica. Both of them are identical down to the last atom, and should be behaviourally indistinguishable (because they have the same physical makeup, materialism states that they must be identical in every way.) But surely you can't be in two places at once! If 'you' survived at all, isn't it obvious that you survive as your original self, not the clone? But what's the difference between your original self and the clone anyway? Both of you would behave in exactly the same way, and both would have the same thoughts (at least initially, when there has been no divergence in the environment). So did you really survive the procedure afterall? If you didn't, doesn't that point to the existence of something other than your physical body including the information contained within the arrangement of the atoms? Is there a difference between the scenario with one original body and one clone, and the scenario where I destroy your original body, and create two(or more!) clones instead? In each case, is it so clear that 'you' will survive, and survive in one of the individuals/clones? My view: I prefer using a more mundane example - one that all of us have experienced: sleep. Each time we wake up, we feel that we are the same person as the one we were the night before, because there is a sense of continuity. The fact that nobody is able to 'clone' us during our sleep ensures that our identities remain unique. Imagine if I clone your body during sleep and destroy the original body, your clone would still wake in the morning, unaware of what has happened. Nobody could ever tell the difference between your clone and your original self. The fact is that when we wake up each morning, we are no more certain that our bodies are the original ones anyway. You would not notice if I replaced your brain with an exact replica. So it is not the temporal-spatial continuity of our bodies that ensure our psychological continuity, but rather, our memories (encoded in a physical form) together with the information-processing apparatus capable of using them. As for the dilemma about 'multiple selves', I don't think my response can satisfy everyone . . . but here it is: I think we should give up on the idea of the existence of an immutable, essential 'core' of ourselves. There are no real selves, only the semblance and perception of them - and it's a mistake to treat such impressions as a 'real' entity. So if I make five clones of you, then 'you' would survive as 6 individuals - even though there won't be a united 'you' who get the experience of all 6 persons at the same time. The question: 'who would YOU survive as?', tempting and obvious it may be to ask, makes no sense because there was never a real self to begin with. So what do you think?