Who Are You?

Last week I Twittered/Facebooked some provocative results from a poll of philosophers. In particular, this little tidbit:

Teletransporter (new matter): survival or death?

Accept or lean toward: survival 337 / 931 (36.1%)
Other 304 / 931 (32.6%)
Accept or lean toward: death 290 / 931 (31.1%)

Yes, that’s all the detail presented in the question: “Teletransporter (new matter): survival or death?” As a professional philosopher, you’re supposed to be familiar with the issue, which I reconstruct as follows. Imagine that someone has invented a working teleportation device. You step in the box, lights flash and sparks fly, and “you” rematerialize in another box, exactly the same in every way, but constructed out of a completely new collection of atoms. The original version of you is destroyed. Did you die? (And then, what if a million years passed in between the two events?)

It would probably be annoying to real philosophers, but I personally put this question in the category of “Not that hard.” And I would phrase my answer as: “Who cares?” What we should care about is how well the teleporter actually works — is the reconstructed person really in exactly the same quantum state as the original one was in? Same memories, feelings, etc? That’s an interesting technology question.

But there’s no interesting question associated with “Did you really die when you were teleported?”, or “Are you really the same person after being teleported?” These are just bad questions. They assume a certain way of looking at the world that ceases to be useful once we’ve invented teleportation. Namely, they assume that there’s a certain “essence of you-ness” that is (somehow) associated with your physical body and continues through time. That’s a perfectly sensible way of talking in the real world, where we don’t have access to duplicator devices or transporter machines. But if we did, that conception would no longer be very useful. There is a person who stepped into the first box, and a person who stepped out of the second box, and obviously they have a lot in common. But to sit down and demand that we decide whether they are “really” the same person is just a waste of time — there is no such “really.”

Which isn’t to say there aren’t interesting questions along these lines, but they are operational questions — how should I actually act, or what should I actually expect to happen, in these situations? — rather than arid metaphysical ones. What if you murdered someone, and then teleported — would the reconstructed person still be guilty of murder? That’s not quite the right question, because it still relies on the slippery essence of continuous personhood, but there’s a closely related sensible question — should we treat the reconstructed person as if they had committed murder? And it seems to me that the answer is clearly “yes” — whatever good reasons we had for treating the pre-teleportation person in a certain way, those reasons should still apply to the post-teleportation person.

The issue of duplication seems much thornier to me than the issue of teleportation. If someone made an exact copy of a known murderer, should we treat both the original and the copy as murderers? (I vote “yes.”) Fine, but what about the view from the inside? Let’s say you have an offer to get paid $100 if you let yourself be copied, with the proviso that after being copied one of the two of you will randomly be chosen for immediate painless execution. Do you take that deal?

I think problems like that are legitimately interesting, although to a great extent their mystery relies on the inadequacy of our conceptions of death. Most of us don’t want to die, at least not right away. But if we did die, we’d be gone, and wouldn’t have any wants or desires any more — but it’s very hard to consistently reason that way. Note that if we replaced “immediate painless execution” with “prolonged torture,” it seems like a much more straightforward question.

This showed up in our long-ago discussion of the quantum suicide experiment. In the many-worlds interpretation of quantum mechanics, you can make measurements that split the wave function of the universe into distinct branches. In some sense, then, you really do have a duplicator machine — it’s just that the whole universe gets duplicated, not just you. Some folks have tried to argue against this idea by pushing adherents into a logical cul de sac. You shouldn’t (to make a long story short) be averse to bargains that leave you dead with large probability, as long as there exist branches of the wave function where you are alive and flourishing — after all, in the branches where you are dead you don’t care any more, right?

My point in that earlier post — a point I somehow managed to completely obscure — was that these are misleading thought experiments, because very few of us would take seriously the corresponding classical suicide experiment. “Here, I’ll flip a coin, and give you $100 if it’s heads and shoot you instantly dead if it’s tails. Deal?” Very little temptation to take that offer. But the logic is essentially the same — if you’re dead you don’t care, right? (For purposes of these thought experiments we always assume you have no friends or loved ones who would miss you; it’s just part of the philosophical game, not a comment on your actual social situation.)

At some point in thinking about the many-worlds interpretation, issues like this inevitably do come up. That’s what David Albert and I talked about a bit on Bloggingheads. There might be a certain measurement that yields result A 10% of the time, and result B 90% of the time. But in the MWI, the measurement splits the universe into two branches, and you end up either in the branch where you saw A or the branch where you saw B. What does it mean to say that you had a “10% chance of measuring A”? You either did or you didn’t — there is no ensemble of millions of you all doing the same experiment. People have made progress on these questions — here’s a talk by David Wallace on his work with David Deutsch in attacking this problem. (Don’t ask me why everyone who thinks about these issues is named “David.”) I haven’t ever looked at this work closely enough to have an informed opinion.

All I know is that being able to teleport around would be really cool.

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60 Responses to Who Are You?

  1. Mark says:

    Knowing what we know of consciousness, you’ll never know until you try it. And even then, you might not.

  2. Haelfix says:

    Well theres the thorny problem that you cant duplicate information exactly. The no cloning/zerox theorem of quantum mechanics forbids this.

    You can get it kinda close to within some accuracy, if you stick enough energy in, and for all intents and purposes you can clone the classical side (which is the one of most relevance for biological processes). So if you are satisfied with close enough, then in principle its possible.

    Also problematic. How do you measure the state of the human body, down to electrical currents et al, all at the same time with no error?

  3. DaveH says:

    Most of the polled philosophers are atheists and realists IIRC, yet the whole idea of “survival” seems to depend on the concept of a soul. That is, as you say, an essence of you-ness. It’s the same thing.

  4. Sam C says:

    The usual problem that gets raised about this picture is one you mention: duplicates. You say ‘The issue of duplication seems much thornier to me than the issue of teleportation’ – but they’re apparently the same issue. Teleporter A produces just one copy of Sam C in the receiver, and we perhaps want to say that Sam C after transportation IS Sam C before, where IS = identity. Transporter B produces two copies, one on Earth and one on the Moon. In the B case, do we want to say:
    1) both Sam-afters ARE Sam-before? But 2 things (2 Sam-afters – we know they’re 2 things because they’re in 2 different places) can’t be identical with one thing (Sam-before).
    2) neither Sam-after IS Sam-before? But how can a double success be a failure?
    3) just one of the Sam-afters IS Sam-before? But they’re identical, so it’s completely ad hoc to pick one over the other.

    Your answer is quite close to Derek Parfit’s in *Reasons and Persons*: the interesting question isn’t the (unanswerable?) one about whether the essense-of-you is teleported, it’s the question: is the person who comes out of the receiver *similar enough to* the person who went in to the sender to count as the original’s survival? ‘Survival’ here means rather less than IS as in ‘is identical with’.

    Parfit suggests that we think of the survival of persons as like the survival of nations or clubs: sometimes their survival is obvious (Scotland tomorrow is ‘the same country’ as Scotland today); sometimes there’s no answer to the question (is Scotland now the same country as Scotland under James I? Well, it covers most of the same territory, it has some related customs and cultures, its cities contain some of the same buildings and institutions, etc., but there’s no further ‘essence of Scotland’ which either is or isn’t still there). What this amounts to is denying that the IS of identity applies to persons over time. I’m not identical with Sam C last year, I’m just the closest survivor of him.

    Some philosophers – including me – are sympathetic to this. Others think we can’t do without the concept of identity of persons in the strong, logical sense of identity.

  5. Sam C says:

    DaveH said: ‘the whole idea of “survival” seems to depend on the concept of a soul. That is, as you say, an essence of you-ness. It’s the same thing.’

    I don’t think so. A soul (i.e. a simple, non-material thing which is you) would be one way to guarantee identity through teleportation (assuming that the soul moves to the nearest appropriate body, and why assume that?). ‘Essence of you’ would be whatever property/ies are required to preserve logical identity (i.e. 1-1, transitive, all-or-nothing identity). Some philiosophers (e.g. Bernard Williams) have argued that the relevant property is ‘having the same body’, where sameness of body requires a continuous history through time and space (so, no teleportation, no uploads, no body swaps).

    In general, views on this problem (usually called the problem of personal identity by philosophers) cut across the theist/atheist divide. The Parfit solution I sketched above is based on the work of John Locke, who was a christian.

  6. Eunoia says:

    If I jumped (Jumper was on TV here yestreen) to the other side of the world,
    surely classical momentum would have me going at Mach 1+ relative to the surface?
    What happens to conservation of mass, momentum etc?

  7. Kerub says:

    I would have voted as “both death and resurrection”

  8. Sean says:

    I like Parfit’s analogy with countries, hadn’t heard that one before.

  9. Alex says:

    Sean there is so much going on here that it is hard to know where to start.

    First: you are right to turn your focus on the duplication problem, since that is what suggests that the person who steps out of the transporter is not the person who steps in. [Imagine the transporter breaks… flash of light. “You’re” still on Earth, and “you” step out on Mars… now there are two persons… since the one can be punched in the face, while the other remains unpunched, they are not numerically identical. At most one of them can be the person who stepped in.]

    Second: the idea that there are answers to these questions doesn’t depend on the idea that there must be slippery essences of selfhood (perhaps you have immaterial souls in mind, or some such). The problem (as far as I can tell) derives from the discontinuity of the change. We might well run the thought experiment with non-human objects like tables — th0ugh the answers would be much harder to care about, since we’re (rationally or otherwise) more interested in our own survival than in the survival of tables. We don’t often care much about the diachronic identity of non-human objects. However, I take it that the reasons for thinking I would not survive the transporter are reasons for thinking that this table would not survive the transporter. [See the duplication problem.]

    Third: from a marketing point of view, defending a view by resting it on the premise that death is not in itself bad for the person who dies, is not a promising tactic.

    At any rate, even if the dead do not mind being dead (since they mind nothing), it is true that most deaths make it true that the person who dies has less of a very good thing than she would have had — had she not then died. That an event makes this kind of thing true is a reason for thinking its occurrence is a bad thing for the person who is deprived of the very good thing.

  10. ARJ says:

    Part of this reminds me of a late night debate some high school friends and I had decades ago: if medical science learns to do brain transplants (and that will probably happen before teleportation), then would they really be doing brain transplants or would it in fact be body transplants???

  11. Stan says:

    For a fun sci-fi read on this topic, you should check out Kiln People, by David Brin. It explores the social and psychological implications of technology which enables short term duplication of consciousness. You really have to stretch your imagination to keep up with the author. (The topic of the novel bears a superficial similarity to the recent movie, Surrogates, but sounds like it is much better done.)

  12. Arrow says:

    The most interesting question regarding duplication is this one:

    You are subjected to duplication – a perfectly identical material copy is created in another perfectly identical room located in some other facility, both rooms have a camera and there are observers watching you and your copy on their screens.

    The question is who do you control? For example let’s say you decide to scratch your head, will the observers see your copy also scratch his head? Will both copies act exactly the same as long as their atomic composition and their surroundings are exactly the same? If someone punched the copy will you fell anything?

    Another problem – there would be no way to tell your original self from your copy if you had a chance to mix together, both of you would claim you are the original and deserve what past, family and material belongings you had before the duplication.

  13. Davis says:

    I actually find it very useful to view me-in-the-past, me-in-the-present, and me-in-the-future as different persons who have significant overlap in traits, experiences, and interests. This view allows for the natural answer to the suicide question: if present actions should benefit future-me, and a current action has a high likelihood of leaving no future-me to benefit, then that action has low utility (anyone so inclined can probably rephrase this in terms of utility functions and expectation values and whatnot).

    This seems somewhat in line with Parfit’s view as described above, and suggests the same answer to the teleporter question: if the person who comes out of the teleporter is sufficiently similar to be considered future-me, then it’s not a problem.

  14. DaveH says:

    sameness of body requires a continuous history through time and space

    Isn’t the ability to infer a continuous history how we actually (re-)identify individuals?
    Even in QED.

    We can infer a continuous history for the body because we have (for the purposes of the thought experiment) a mechanism, teleportation, which explains how the body got from A to B.

    What I’m saying is that the assumption the question is interesting requires more to “survival” than mere identification of the body.

    I see why Sean answered it “who cares?” now.

  15. greg says:

    Yeah, the teleporter/duplicates idea is a fairly interesting one. There are different formulations of it, but generally speaking it’s a modern version of the Ship of Theseus.

  16. Michael Albert says:

    Further discussions/uses of this issue in literature/film: “The Prestige”.

  17. George Musser says:

    Has anyone ever calculated how long it takes for all the atoms in our body to be turned over — that is, to be excreted and replaced with atoms from the air or food? (Like the ship of Theseus.)

  18. Davis says:

    The question is who do you control? For example let’s say you decide to scratch your head, will the observers see your copy also scratch his head? Will both copies act exactly the same as long as their atomic composition and their surroundings are exactly the same? If someone punched the copy will you fell anything?

    Doesn’t this presume a “you” that exists independently of the copies, and thus beg the question? I think if you dig deeper the interesting question is, can you turn these into interesting questions without independently assuming an essential self?

    Under my view (in my previous comment), the first question does not make sense: I see them as two mes-in-the-future, so “I” don’t control either one. The second and third questions can be rephrased as “when will the behaviors of the copies begin to diverge, and why,” which under my view is more of a biological question, and so not philosophically exciting. And the last question is easy after removing the presumption that one of them is “me”: they’re two separate people, so clearly one would not feel the other’s pain.

  19. Sto says:

    Here is a video illustration of the same question:

  20. How could duplication be possible without also duplicating the physical environment–space time the whole shebang? The instant the ‘duplicate’ and ‘original’ begin to interact with and adapt to their respective environments, they would no longer be the same. More like monozygotic twins..

  21. Aaron says:

    We know that subatomic particles have no identity. The answer is not “who cares”, but that there is no difference between a state that has been teleported exactly, and one that moves via some other method.

  22. Zwirko says:

    The Star Trek transporters convert the object to be transported into steam of particles known as the “matter stream” – so you are reconstructed from the same atoms (I think). And don’t forget the Heisenberg compensators…

  23. greg says:

    @Jacob Russell (#20) and @Michael Albert (#16) – you might also want to check out Algis Budrys’ Rogue Moon. It involves the repeat duplication of an individual and how the original and duplicate interact and identity is maintained (the original is put into a sensory-deprivation chamber and is able to maintain a mental connection with the duplicate, until the duplicate is killed.)

  24. Arrow says:

    Davis: “Doesn’t this presume a “you” that exists independently of the copies…”

    The first question is really about the nature and origin of consciousness.

    “You” means your consciousness, the question does not presume it is independent. The whole point is that now you experience and control your body and your body only, but what is it that ties your consciousness to this particular body and not the other?

    If your body will be perfectly duplicated will your consciousness extend to the new copy (making you aware of two bodies at the same time which seems rather unlikely but who knows) or will the new consciousness be created as a result of duplication? And if the later what will be the factor determining which body your original consciousness can control knowing that there are no differences between the bodies?

    The second question is about free will, if both copies will act exactly the same in the exact same situation there is no free will.

  25. Matt says:

    It seems to me that all this boils down to timing. For the teleportation problem, George (#17) points out something important: Physically, none of us are exactly the same person as we were yesterday. We have new atoms incorporated into ourselves, and older ones have been discarded. Would anyone argue that I die every time I lose an atom, and a new me is born because I have a different atomic identity? Hardly. Now, to fully change out my atoms takes a long time, and no doubt during that time I will be a significantly different person, but that’s a matter of timing. Let’s say that I was able to fully reconstruct myself in an instant, without invoking teleportation. I flip a switch, and every one of my atoms is switched out for an identical but different atom. Am I a different person? Would I be absolved of my crimes of honor-bar candy theft? I think not.

    Now mix in a little teleportation. I flip a switch, and the reconstituted me ends up a couple of inches to the right. Same me – a change in location and a change in physical make up does not imply a change in identity.

    As for the duplication problem (?) Sean, I gotta disagree that the logic between the classical and quantum suicide problems (as you’ve identified them) is the same logic. In the classical, you have a 50/50 chance of survival when the game is completed. In the quantum game, you (the you before duplication) has a 100% survival rate.

    Here’s the more relevant question: If I offered to make an exact copy of you, then pay you $100 and make you watch yourself get offed, would you care?