Teleportation: why you survive

This is a belated follow-up to a post I wrote almost two months ago, in which I polled my readers as to whether teleportation (understood as destroying a body after recording its exact structure, sending the information somewhere else and re-constructing it there) would kill the original person and create a different with false memories, or whether the original person would survive as the teleported one. (If you missed that post you would do better reading it and the comments discussion before this one.) The results were 5-3 in favour of survival (6-3 including myself) but my friends Merrick and DrNitro voted for death, and this post is an attempt to convince them and other skeptics of why I would not be afraid of using such a machine, in the extremely unlikely case that it becomes technologically possible in the course of my life.

Let us first assume without discussion that the “self” does not reside in an inmaterial soul. I think my friends agree with this assumption. Their certainity that the teleportation experiment kills you is grounded in the implicit belief that you are essentially your body, and destroying your body destroys you. But this is not completely exact, because they would probably agree with me that you could survive the destruction of any part of your body, or all of them, with the exception of your brain. If my brain is kept functioning (perhaps in a vat, as in the old Matrix-like philosophical scenario) then all the rest of my body can be destroyed and I will surely survive. So the only question is: Is my survival tied to the survival of my concrete, material brain, or only on the survival of a pattern of brain structure, enconding my personality traits and memories, such that if a new brain comes to exist with this same pattern I continue living in it?

I will give now two arguments (actually, two thought exeperiments or “intuition pumps”) for the second option.

First argument: Suppose we perform the teleportation experiment with a guy –call him Ernest- while he is in coma or deeply anaesthetized. Suppose that we don’t destroy the original Ernest, but only scan his body and send the information to create a duplicate Ernest. (Technical note: as commenter Dmitry remarked, this is physically impossible if the teleportation must copy the exact quantum state of the original, as that is impossible without destroying it. I am assuming that the features of brain structure responsible for the self do not depend on the quantum state.) While both are still unconscious, we lie them side by side and randomly mix them up, so nobody can tell which is the original (not even us, if the randomization and arrengement is made by a computer that doesn’t save the information). Now we prepare to kill one of the copies and awake the other one.

According to my friends, it matters a great deal which copy we destroy. If we kill the original, we are murdering Ernest, and the awoken copy will be just an imitation with faked memories; while if we destroy the copy before awaking it, nothing bad has happened and Ernest goes on living normally. But how can this be? Both bodies lying there are completely identical in every detail that matters. Setting aside random influences that may have changed them since the duplication (which would have affected any of them with no preference) they will react in the same way if awakened, remember the same things, feel the same way. Which body was the original and which the copy is what Daniel Dennett would call an “inert historical fact”. It is a fact purely about the past, that cannot affect anything anymore in the present or the future. How can whether Ernest lives or dies depend on this fact?

To make this intuition stronger, imagine that the experiment is done with the brains. We first destroy Ernest’s body keeping alive in a vat his unconscious brain; we all agree that this doesn’t kill him. Now we duplicate the brain and mix up the two copies. We have in front of us two brains in two vats, exactly alike in all neronal details; any of them if awoken would claim to be Ernest. Unless we believe that there is an invisible soul mystically attached to the original brain of Ernest, how can it matter for his survival which of the two we choose to awake? If thought and consciousness are just brain activity, and the same brain activity would go on in both brains, then any of them we choose to awake will continue Ernest’s life equally well.

This was my first argument. My second one involves a different series of modifications we can make to poor Ernest’s brain. Let’s take anaesthetized Ernest and perform on him any of the following operations. (Assume they are technically possible –even if they are not, I don’t see any impossiblity in principle going on here, surely not more than in the teleportation experiment):

a) “Freeze” his brain so all living signs are completely disappeared, and then “relive” him.

b) Same as above, only that while the brain is “frozen” we cut separate a small part of the brain and then “patch” it together with the rest in exactly the same way it was. (We can decide how large to cut this piece, from a very small one to as much as half of the whole brain).

c) Same as above, only that instead of cutting only a part we cut his whole brain in many little pieces, and then put them back together again.

d) Same as b), only that we duplicate with our teleportation machine the separated piece and use the duplicate instead of the original to reconstruct the whole brain.

e) Same as c), only that we duplicate all the pieces and make the complete brain using the duplicates, or perhaps some of the duplicates and some of the originals.

Now, question for those who believe teleportation is death: In which of all these cases is the brain/person that awakes after the operation Ernest, and in which it is not Ernest but a mere copy and Ernest has died? For me, this is a non-question; the person that awakes has in all cases Ernest’s personality, memories, etc, so he is Ernest and it doesn’t matter which parts of the brain are originals and which not, or whether the brain has had a continuous uninterrumpted existence as a whole object. But for those who disagree with me there has to be a difficult question in deciding where to draw the line: they should say that Ernest has died in case e) (which is very similar to the original teleportation scenario) and that Ernest is still alive in case a), but what of the intermediate cases? Exactly how much of the original brain needs to have persisted for Ernest to survive? Any answer seems to be arbitrary. The simplicity and non-arbitrariness of my answer to these questions seems a good argument for my position.

Thoughts…?