Perry – A Dialogue on Personal Identity and Immortality


The First Day:


Weirob’s Challenge to Miller (p. 397):  Show me how it could even be so much as possible that I survive the death and destruction of my material body.


Definition of Survival (397): To survive means that there would be someone for whom it would be appropriate for me to anticipate having their future experiences.



Miller’s First Attempt (p. 398):  This challenge is easily met.  You are here now, and then in the future, there will be someone who is you.  “Two people meet a thousand years from now…”


Weirob’s response (398): But how can I say that that future being will actually be me (or that I should anticipate having their experiences)?  Think of a Kleenex box; if we reduce it to ashes, we would never be inclined to say that we’ll encounter that very same box.  No matter how similar any other future box is, we’d never identify it as the original one.


The moral: exact (or very close similarity) similarity does not amount to identity.


The Problem of Personal Identity:  How do we identify one person at one time as that same person at another time?



Miller’s Second try (399): But there’s something special about us.  Unlike Kleenex boxes, we have immaterial minds or souls that allow us to track identity across time.  To say that one person is identical to another is to say that they have the same immaterial souls.


Weirob’s response: So how does one go about judging whether or not someone we encounter has the same soul as someone we encountered previously?  The problem is especially acute since souls are assumed to be so intangible.  In practice, we simply assume a bodily criterion for personal identity.


Miller (399): Well, at least here on Earth, there is a correlation between bodies and souls.


Weirob: But given the intangibility of souls, we cannot have any independent basis for establishing or confirming this correlation.  Souls, in this respect, are unlike caramels. (400)


Miller (401):  But why can’t we use psychological characteristics to judge sameness of souls?  I know that someone is you based upon their personality, etc.


Weirob (401): Once again, psychological similarity does not amount to personal identity.  What we need is the appropriate connection with a future self; otherwise we couldn’t properly “anticipate” having their experiences, no matter how similar their states of mind are to ours. 


Analogy with the river: what allows us to say that the river we see here is the same as the one over here is that they are appropriately connected.



Weirob’s wrap-up (402-3): If judgments about personal identity were grounded on judgements about the identities of immaterial souls, then personal identity would be completely mysterious.  For there’s no evidence we have to prefer the presumption that our body has but one soul attached to it as opposed to alternative theories that have our bodies changing souls as often as we change underwear.


But personal identity is not at all mysterious.  We simply employ a straightforward bodily criterion.


It follows (by Modus Tollens) that judgements about personal identity are not grounded in the reidentification of one’s soul.


The Second Day:


Miller’s opening (p. 403-4): Consider waking up; now surely we can tell who we are before or independently of considering what body we happen to possess.  If that’s right, then it would seem that Weirob’s bodily criterion for personal identity wouldn’t be quite right either.


Weirob (404): Perhaps we are simply assuming that we are waking up in the same body.


Miller  (404): Still, doesn’t all this show that we could imagine waking up in a different body?



pp. 405-6: The discussion then turns to what the appropriate connection between the different stages (or “temporal parts”) of a person would be, to unite them together to form the same enduring person.


1)  Spatial connection unites (or “stitches”) the various parts of a river together.

2)  Continuity in score-keeping practices unites the various plays in a baseball game together.



Miller’s Idea (406): Perhaps the different stages of a person’s life are united by being part of the same “stream or flow of consciousness,” connected one to another via memory. [Locke]


Weirob’s reply (407): We need to distinguish actually remembering some event in one’s past from only seeming to remember it.  Many folk might sincerely claim to remember experiencing events from Napolean’s life, but we tend to think of those folk as looney.  Shouldn’t we say the same about anyone in a separate body who claims to share my memories?  “But doubts about survival and identity simply go over without remainder into doubts about whether the memories would be real or merely apparent.” (p. 408)


In practice, we simply rely upon a bodily criterion for distinguishing real memories from phony ones.



Cohen (408-9): Perhaps we can employ a causal connection between experiences and memories of those experiences that transcend one’s body.  That is, perhaps a future heavenly being might have memory impressions of certain events because those events happened to you on Earth.  Mightn’t we say of such an individual that they would be you?


Weirob (409):  No, we shouldn’t.  For if one such being were created, couldn’t there be others as well?  Each of them might have equal claim for being identified with the original.  But if we grant the idea that they are identical to the original, then the transitivity of identity would seem to mean that they would be identical with one another, which would be absurd.


Cohen (409): But what if only one such being were created?  Wouldn’t we say of it that it was you?


Weirob (409-10): This idea seems to make personal identity depend upon factors outside the beings concerned (“extrinsic factors”) – namely the non-existence of competitors.  And this just seems “odd.”  I could then be “killed off” (or one heavenly being’s identity with me cease) simply be the creation of another “Heavenly Gretchen.”


[Now apply the considerations of this day to “Transporter mishaps,” etc.]




The Third Day:


This time Cohen begins with another challenge to the body criterion.  Suppose one’s brain was transplanted into another person’s body (or should we say another body hooked up to one’s brain?).  Would we identify the survivor with the original brain donor or with the original body donor?


Cohen reckons that we’d be inclined to identify the survivor with the original brain donor.  If so, then it would at least seem possible for the same person to have distinct bodies, and so the Weirob’s body criterion would be flawed. (p. 411)


Weirob disagrees (p. 411):  Why can’t we just say once again that the survivor only seems to remember being the brain donor. [Here I wonder whether Weirob might be surreptitiously changing the terms of the debate.  Originally she asked for an account of how one could imagine continued survival in a different body, whereas now she seems to be demanding how one must understand it that way.]


Cohen:  But most (including the courts) would naturally agree that the concept of concept of personal identity should follow brain identity (p. 412)


Weirob: But this line of reasoning seems to make the issue of personal identity more a matter of linguistic or cultural convention, which it intuitively is not.  The courts (or the majority) clearly cannot simply legislate whose future experiences I can anticipate having.  Personal identity cannot be a matter settled like that. (p. 412)


Cohen: But as a matter of fact, don’t psychological characteristics overwhelm bodily/physical characteristics in our considerations of personal identity? (p. 413)


Weirob:  Consider now an alternative to brain transplantation: brain rejuvenation, where an old brain is reconfigured to mimic the operations of another’s brain. (p. 414)  Surely (especially under the proposed brain criterion of personal identity) we wouldn’t be tempted to identify someone with a rejuvenated brain with the original subject whose psychological characteristics were being duplicated. (Why? Well if we could do the rejuvenation once, we could do it many times!)


Now suppose you woke up and suspected you had been transplanted into another body.  The trouble is that you couldn’t know whether your original brain has actually been transplanted into another person’s body, or whether the brain you now have has been rejuvenated with another person’s psychological characteristics.  Under the brain criterion of personal identity, you couldn’t actually tell who you were!  (P. 415; this point also tells against Miller’s supposition from the second day that you could always tell who you were without having to consult your body.)


In general, you don’t really know which brain you have; so the brain criterion of personal identity makes issues of personal identity even more mysterious.  Cohen, you are irrationally connected to your brain.  (p. 415)


Cohen:  But really now, what is so egregiously wrong about identifying the survivor with the brain donor?  Indeed, perhaps it was misguided to construe the issue of continued survival in terms of personal identity in the first place, since that only seems to invite the transitivity problems. (p. 416)


[Invites considerations about imaginary creatures that fission and fusion (Parfit people).  In all likelihood, they would not construe the issue of personal survival in terms of personal identity.]