Hi Tom

An eerie parallel to your example of two copies trying to figure out who is who is experienced by people with diffuse epilepsy who have had their corpus collosum divided. While it works fine at stopping the epilepsy what is observed is that the two separated hemispheres of the brain act like distinct personalities - literally two people in the one skull.

Personally I think that the soul, even if it isn't the brain itself, is actually generated by the brain's specific patterns of electromagnetic activity. In principle this unique pattern could be copied but the accumulation of diverging experience would cause the "copies" to become distinct people - that was the copy's discovery in Arnie's "The Sixth Day", that he was not the original and he didn't have to be. Thus - regardless of how he was "born" - he was free to be just another Person.

Now whether that means immortality is ruled out for everyone who is planning on making body duplicates I really can't say - Is a copy is as good as the original when the original has turned to worm-food?

Personally I'd rather be disassembled and reassembled in a new medium bit by bit and see if it felt different directly. Thus I'd settle for nanomachines replacing my neurons with new cyber-neurons or the like. If the transition was smooth then I suspect I'd never notice. After all if an Alzheimer's patient is cured by growing new brain cells when is he/she the original and not a copy? After 10% brain replacement? 50%? 80%? If someone gets a bionic hippocampus are they suddenly a different person? All these medical procedures are becoming real possibilities so the issue is not as abstract as we might imagine.

You can hopefully see what I mean.

Adam