Another metaphysics post, this time getting away from Kripke and language:
One example introduced on the first day of the metaphysics class I'm taking was of a 17 year old slacker who goes off, spends three years in the military, and as a result changes significantly in character, is more disciplined, etc. When he gets back, he reports, "I'm a different person now." Philosophers, being philosophers, may be inclined to ask in this situation whether this might literally be true.
It sounds silly, but I've thought of another thought experiment that suggests something significant may be going on here. Imagine a person is kidnapped by time travelers, whether from another planet or a future Earth it matters not. In addition to time travel, their technology includes great medical and genetic technologies, which allow the subject to be kept alive indefinitely. Over a course of ten thousand years, he goes on many adventures, entirely forgetting his original life for all practical purpose, and his genetic code is slowly altered, one tiny insignificant bit at a time, until it is unrecognizable. Maybe he has some vague ideas about what it was like to live in his home milieu, and maybe his genetic code could be recognized as originally human, but both memories and genetics have been altered (slowly, over the course of ten thousand years, remember!) to the point where he could never be identified with a single individual.
To complete the thought experiment, imagine that somehow the time traveling technology finally places him back in his home setting, an hour or two after the abduction. Would it make any sense whatever for the subject's previous friends and family to treat him as in any way the same person? I think not. I dare say he would not be the same person. This is in spite of the fact that the example is different only in extent from the military case, and I have stipulated that the change is completely gradual. It is interesting to think that the ex-slacker will likely not interact with many of his old friends in quite the same way, especially if they themselves have remained slackers. The time traveler is only a more extreme form of that.
4 comments:
How can one postulate about time travel if one does not know precisely how time works? One must remember the limitations of human knowledge, here .
How does one treat, for example, telescopes that see to the edge of the known universe?
Silly metaphysicists.
-Katharine
It's just a device for asking if it makes sense to treat him as the same person. If you prefer, imagine the subject's friends and family being put in cryo-stasis.
If personhood derives, at least in part, from continuity of consciousness, then no, he is still the same person. A person who has been significantly altered by a dramatic series of experiences, but the same person.
If personhood derives from memory and accessability of consciousness, then of course not; you've wiped both the memory and even the genetic identity of the time traveller clean. But then again, if that is the case, none of us are the people we were in the past. Physically speaking, memories are complex chemical-electrical patterns embedded within our brains. We use those memories by accessing those memories, but the process of accessing them causes the pattern to be erased. So the brain must attempt to reproduce the memory, and sometimes mistakes are made. Thus do our memories alter over time. Biological data corruption, if you will.
So we are always different people than we were in the past; we've acquired new experiences and our recollection of old experiences will have been altered, slowly and over time, as surely as your time traveler's were. Nevertheless, it seems to make sense to treat people the same as they were before, so we can maintain relationships with individuals.
>If personhood derives, at least in part, from continuity of consciousness, then no, he is still the same person. A person who has been significantly altered by a dramatic series of experiences, but the same person.
I had a prof who said that if he believed that theory of identity, he would be very worried about going to sleep at night.
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