I am currently watching the Yale open course "Philosophy of Death" with Shelly Kagan. So far he has made the case that there is not good enough reason to believe in the existence of an immaterial soul. Thus everything is now being argued mostly from a physicalist perspective.

He is now discussing personal identity, specifically the perspective of personality theory of identity which says

Your personality (beliefs, desires, memories etc etc) is what makes you you. Although your personality may change across space-time, the entire continuously connected space-time worm of beliefs, memories, desires, etc etc is your personality and forms your identity.

We are presented with roughly the following science-fiction thought-experiment:

Imagine I die and a scientist is able to copy the information from my brain that composes my personality and then is able to load (implement) my personality onto the brain of some other dead body, John Smith from Iowa. Certainly "I" would awake with my same (space-time worm of) desires, beliefs and memories but in the body John Smith. Based on the personality theory of identity, this person would be me. Now imagine the scientist loads my personality onto another dead body, Kris Kringle from Florida. Are the person in Iowa and the person Florida both me?

We only have three options:

  1. Only one of the two are me.

  2. Both of them are me. Meaning the space-time worm that was just one me has now split into a two me's, one in Iowa and one in Florida.

  3. Neither is me.

As there is no reason to logically accept one as me and the other as not, option 1. cannot be the case.

Option 2. directly follows from the personality theory of identity as stated above. Kagan immediately dismisses this as absurd and therefore appeals to option 3. (requiring a revision of the personality theory by adding a no-splitting clause). However Kagan does not elaborate on this dismissal.

Why dismiss option 2?

Edit for further simplification:

1st premise (soundness aside)

Personality theory of personal identity:

You := your personality (whatever that is)

2nd Premise

Your personality is transferable and copiable to different objects in such a way that preserves it.

3rd Premise

Your personality has been copied to two different objects A and B.


You are A and you are B. (Option 2 and not option 1 nor option 3)

What is wrong with this conclusion?

Furthermore, what is so repulsive about the idea in general?

  • 1
    My apologies, I just realized I tried to pack to much into a question. I hope this communicates the question better. – Jared T Nov 20 '16 at 3:24
  • This question is already answered here philosophy.stackexchange.com/questions/38515/… Short answer: self-identity is a matter of convention, not fact, and adopting a rule for it (like contiguity) is a practical issue depending on context, not a "logical" one. Also, "copying the information from my brain that composes my personality" after death is likely non-sensical, "personality" resides in dynamic neural patterns, not static 0-1 storage, after their termination there is nothing to copy. – Conifold Nov 20 '16 at 21:50
  • Without any external basis, the first objection that occurs to me is that this shared identity can continue only for a vanishingly small length of time. As soon as the one of you has a different POV on the world from the other upon opening his eyes, you no longer have the same set of memories. Even if the two of you have different unconscious experiences of the lab tables or the currents in the vats that make you, before you become fully conscious, you are different identities, according to the definition. – user9166 Nov 21 '16 at 2:58
  • Conifold, thanks for your comment. Are there any resources you would recommend that talk more about fact vs. convention of language regarding self-identity and other things? Also, I did not mean the details hypothetical to be taken literally, only the net result - that the personality is copied. Maybe done by copying the final system state to a different medium and then continuing the pattern of the dynamics within that medium. It certainly isn't possible now nor will it likely ever be. But given that static rules can give rise to dynamic behavior, is this really nonsensical? – Jared T Nov 21 '16 at 3:21
  • jobermark, in the hypothetical, while both people are now different from each other, they are both extensions of the original personality and are both by definition that person. – Jared T Nov 21 '16 at 3:24

I'll try to find the source material link... but David chalmers recently had a "debate" (more of a spectated conversation) about this, in a general way. The topic of AI was investigated quite a bit, and some panel members seem to have agreed that even swapping consciousness to another brain is still a from of AI, and they also went into some of the problems you've presented. I.e., two different swap recipients, etc. I saw a video of the debate, but can't find it right now. Try looking for that....

  • Thanks I will check him out. He has a lot of interesting looking books on mind and consciousness as well. – Jared T Nov 20 '16 at 3:08

The thought experiment suffers from the same problem that many of these thought experiments have, there is a leap of guesswork which renders the whole experiment nothing more than idle speculation, to presume that anything of any use could come from it is ludicrous.

Certainly "I" would awake with my same (space-time worm of) desires, beliefs and memories but in the body John Smith.

...is an absurd thing to say, neuroscientists barely understand how the brain-body interface works as it is, how would all the severed nerve endings respond to being rejoined for a start. Take a look at the work of neuroscientists like Ramachandran who work with people who have severed limbs, many of whom have phantom limb syndrome, or even the more severe phantom limb delusions.

Your personality (beliefs, desires, memories etc etc) is what makes you you... Option 2. directly follows from the personality theory of identity as stated above.

... So we now have a classic information-less dichotomy, that always arises in these types of experiment. Either the first premise is wrong, or our instinctive desire to reject option 2, as our instinctive desire cannot be trusted (who would instinctively believe quantum theory over Newton?), we have absolutely no idea which, nor can any degree of "thought experimentation" which relies solely on matching up answers to our "instinct" provide us with any insight.

There is no good reason to dismiss option 2, neither is there any good reason to dismiss options one and three.

It could well be that the concept of "me" is entirely subjective and arbitrary and so the first living body the personality is loaded into becomes "me" and rejects the claim of any subsequent bodies to such an extent that future self-identities form entirely from that rejection (option 1).

It could be that the concept of "me" is not singular and only appears so because no such technology exists, should this capability ever be invented, some years after we might happily talk about the multiple "mes" (option 2).

Or, it could be that the concept of "me" is inseparably linked to our bodies and so would not transfer over to another body (option 3).

The point is we have absolutely no way of knowing because no-one has created a falsifiable theory, you might as well ask my Grandma what she reckons as find out why Kagan dismissed the idea.

  • There are many reasons to question the soundness of the assumptions, however I have reformulated in a more direct way - see edit. I think many people would like to believe Premise 1 and Premise 2 is a direction in which modern science is trying to go. So are you saying there is no value in seeing where these assumptions take us logically? – Jared T Nov 20 '16 at 17:34
  • @JaredT I think you're right in so far as there is no reason not to see where that leads, but I also think you've already done it. It leads to the conclusion that "you" must be both A and B, from your premises as laid out. The trouble is we then have no way of knowing whether our instinct (which wants, in many people, to reject the conclusion) is wrong, or the premises are wrong, so the investigation stops there. Certainly interesting up to that point, but has no further to go. – Isaacson Nov 21 '16 at 8:07

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