Same old argument...
Someone makes an exact duplicate of me. Nanites have made it a perfect copy of me, atom per atom. Even its brain, memories and thought processes are identical to mine. It thinks it is the original and will probably act in any situation just like the original.
Is it "me"? This is a semantical question based on the definition of "me". The question is probably unanswerable because there is no good definition of "me". Everyone currently has an unalterable viewpoint from within a single body. This viewpoint always defines the self. When copies are made, there are multiple bodies with similar programs running in them. The concept of "me" no longer applies in the same way. New definitions must be made. The old definition does not apply. So the answer is probably that both of the resulting individuals are equally "me"?
Is there any difference between the two individuals? No. Both are functionally the same. Neither the copy or the original can tell the difference. No one else can tell the difference. If the original were killed and they copy continued in its place, the result would be the same as if the original had continued. I think everyone agree with this(?).
Is there any rationale for killing one over the other? No. They are identical in every way, including memories and thought processes. The idea that the original has more of a right to live or claim the identity of "me" than the copy does not make sense and cannot be proven or distinguished between the two individuals.
Would either individual agree to commit suicide based on the fact that the other would continue in its place? I say no. Others would say yes. I have a deeply personal desire to live and to continue on forever. I'm not sure why I feel this way. It may be based more on fear of death than anything else. I do *not* think it is based on an altruistic desire to provide some functional usefulness to the rest of the universe. Just because a replacement has been found who can do the job of "me" just as well, that does not mean that I want to quit my job of being "me". I still would be a functional individual. After the copying process produces two individuals that think as "me", I believe both of them would continue to hold this belief. Both would equally try to avoid death, and would probably mourn the loss of the other.
Is death a personal loss, or a loss to others? Some would allow one of the copies to be killed based on the theory that the other can replace it. However, this implies that the value of a life is not based on the individual's value upon their own life, but upon the value that life contributes to others. If an exact copy can contribute to others in an identical manner, then the original can be killed with no loss to others. But the individual may not want to be killed. The individual would be alive, experiencing life, and might not want that experience to end. Is the "life" to be measured from the individual's point of view, or from the point of view of others?
Would my stream of consciousness somehow jump from the original to the copy when the original is destroyed? I see no scientific basis for this. The two are separate individuals with no mystical connection. When one ceases to function, it no longer continues. Just because another replacement can predict what the dead copy would do next does not mean that the dead copy is not dead. After the copying, there are two people, no matter how similar. After one is killed, there is one living person and one dead body. I can see no rationale for saying that the body is not dead or that the person has not been killed just because there is a suitable replacement for the one who was killed. Before the killing there were two persons with my qualifications who can perform work. After the killing, there is one less such persons.
Conclusion from all this rambling: I don't want to avoid death based on what I can contribute to others. I don't even try to justify my contribution to the universe as a justification for my continued existence. I want to continue living because it's fun, because I like experiencing things, and because I fear having input to my experience simply cease. Having an exact duplicate of myself does not change my feeling. I think we need a better definition of why we want to live at all. For those who only live to be functionally useful, they may not mind dying if a perfect replacement is found or made. For those who just want to experience life, I don't think any substitute for personal growth and survival would be acceptable.
-- Harvey Newstrom <mailto:firstname.lastname@example.org> Author, Engineer, Entrepreneur, <http://www.gate.net/~harv> Consultant, Researcher, Scientist. <ldap://certserver.pgp.com>