From: Lee Corbin (lcorbin@tsoft.com)
Date: Thu Oct 31 2002 - 18:14:59 MST
Hi gts,
I see another delightful thought experiment here. I hope
you will forgive me for reading it carefully line by line
and replying. Normally I like to quickly scan an entire
post first, but in this case, you are entitled to my
reactions as I have them. Thanks.
> Lee,
>
> 1) Bob gets forked into Bob1 and Bob2.
> 2) Jack, a friend of Bob's, has no knowledge that his old friend Bob has
> forked into Bob1 and Bob2.
> 3) Bob1 visits Jack on the day after the forking.
> Jack cannot, by any means possible, determine
> that his old friend Bob has forked.
Okay, that's fair. Jack does not have any outside information.
> 4) Then along comes Bob2, who joins Jack and Bob1 at lunch.
> 5)"Strange," says Jack, "I thought there was only one Bob!"
> 6) Bob1 and Bob2 both say they think they are the same Bob
> Jack has always known.
> 7) "Maybe so," says Jack, "But I suspect you two are nevertheless
> different people. Allow me to conduct a thorough survey of your
> personalities."
Even with the case of identical twins, who have been separated
from birth, this is no small task. If the duplicates are only
a few minutes old, Jack is going to have one hell of a time!
> 8) Jack then tests both versions of Bob with an exhaustive set of
> personality tests.
> [Jack finds that Bob1 likes pizza better than Bob2]
>
> 9) "Strange," says Jack, "you two appear to be exactly the same person,
> except that Bob1 likes pizza a lot better than Bob2.
> I wonder how that can be!"
Duh! Sometimes **I** like pizza better than at other times.
There's nothing new in that! My mood and eating preferences
clearly change during a single meal. If you think that that's
what makes up a person, [deleted]. My food preferences have
extremely little to do with who I am as it is. But under the
usual conditions, Gordon, what we mean by "food preferences"
doesn't even change for people, except over months. That's
because everyone knows that after a meal you'll like some
foods better or worse than before (for a short time), or,
guess what, you might not even feel like eating! That hardly
makes you a different person!
What makes up a person, gts, is his or her memories, personality
dispositions, beliefs, and so on. That's why I am the same
person you keeps writing to you in this manner in this thread.
> 10) "Oh!" exclaims Bob1, "I guess I should mention here that I stopped
> for pizza on the way home from the fork-master clinic. It was the best
> darned pizza I ever had! I'm definitely going back for more next time I
> get a chance."
> 11) Jack then concludes rightly that Bob1 and Bob2 are not the same
> identity after all, even if they are very similar.
Wrong. Your concept of "identity" is so rigid that it is
completely useless. By your lights, no two articles above
the molecular level have ever been identical in the history
of the universe.
Despite their similarity, the terms "personal identity" and
"identity" as used in physics are not the same thing. A person's
identity is what distinguishes him from other people of his
tribe or nation. We also say that one's identity doesn't
change from day to day, but we clearly mean *personal identity*
here. Likewise we consider that the Mississippi River remains
the same river from day to day.
Or does the word "same" in the preceding paragraph annoy you.
Do you think it best for us to stop speaking of the Mississippi
river as an entity?
> He realizes it would be absurd to consider them to have the
> same non-nominal identity, because when Bob1 refers to himself
> as "I" or "me" he is referring to someone who rates pizza as
> a 7, and when Bob2 refers to himself as "I" or "me" he is
> referring to someone who rates pizza as a 4.
Why even concoct such an involved example? As soon as a fork
occurs, one duplicate will be sitting in a room "over there"
and another "over here". One will admit "I am here near the
door, not over there", and the other will say "I am here, not
over there near the door". What we are debating is (1) whether
"Bob" survives if only one duplicate does (2) whether one
of the Bobs should look forward to waking up the next day
even if "he" is the one that's going to be killed.
(I admit that the latter is much more difficult that the
former, but, so it happens, equally true.)
Lee
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