At 16:01 -0700 20/06/2002, Hal Finney wrote: >It's not clear that it means anything to say that the person could have >died. Here is why I say that. > >I think we agree that the person in the mechanical brain who leaves >the operation will not be able to tell whether it was a success or not. >He will have memories of going into the operation and coming out of it, >but is that good enough? No, even if he is in your sense a new person, >he would still have those memories. So the memories mean nothing. > >The problem with this reasoning is that it is consistent with the >possibility that we die in this same sense every night when we sleep. >Perhaps the person who wakes up is not the same person who went to sleep. >He has memories of falling asleep, just as the mechanical man has memories >of going into the operation. But we just agreed that the existence of >such memories proves nothing. > >In fact, I don't think there is any way that we can ever prove that our >"identity" is maintained across sleep, or unconsciousness, or for that >matter from one moment to the next! Maybe we are dying every instant, >but we can't tell, because we are constantly being re-created with our >memories of the previous events. > >Given that there is no way for the subject or any other person to tell >the truth or false of this, isn't it possible that there is no truth or >falsity to tell?
No, because once we accept we have mechanical brain then godel-like theorems could in principle be applied to us and this can be used to show indirectly that there are true propositions about us that we cannot prove. Anyway there are other powerful argument showing that we should not equivocate truth and proofs. Now you are right if we are mechanical device we cannot prove we "survive" any instant, that's why I use logics in which we survive any instant almost by definition. The real problem, then, is to explained the stability of our best and short explanations (like physical laws). It is not wrong (with explicit comp) to say that we are dying at each instant, but this is quasi-meaningless. Bruno