Pondering on those who argue consciousness is purely a physical phenomenon one day, I designed a thought experiment, (but shortly found that it was an elaboration of a thought experiment, proposed by McGinn in 1999 (although I think mine carries more oomph)).
Leonard McCoy, the doctor in the original Star Trek TV series, did not trust the transporter, a device that beamed you from one place to another by splitting you up into your constituent atoms and sending them from here to there in the blink of an eye and reassembling them on the other side. He was very unsettled about being broken down and being put back together (perhaps he had seen the 1950s movie The Fly and had been concerned about the potential for error in such a machine). But there may be a bigger problem than McCoy realized.
First, by hypothesis, assume physical materialism is true and that atoms are all there are in the universe.
Now suppose you had a device that could examine every atom in your body, and then grab some atoms out of box (labeled Atoms) and make an exact copy of you, placing every kind of atom from the box into exactly the same place it was in you and in the same state (the possibility of constructing such a device is irrelevant to the thought-experiment; I recognize that the copy machine would have to break some of Heisenberg’s uncertainty rules, but indulge me here).
You face south and turn on the machine, and it makes a copy of you and places it facing north. Since both of you have exactly the same memories, (it has copied all of your neural hardware including the chemical state of each atom at the time the copy was made), the only way that she and you know which is the copy and which is the original is by the direction you are facing (how unsettling to have a complete complement of memories implying a continuity that is not there—but you know you are a copy because you are facing north). There you are, looking at a copy of yourself. There is still the you-you, the person “looking out the window” of your eyes, the subjective self, the thing you recognize as your unique consciousness.
Now, however, there is another copy of you looking at you. Both of you know who is the copy and who is the original by the direction you are standing, yet from that moment on, two existential entities are experiencing different subjectivities. You have no more access to the subjectivity of the woman across the floor from you than you do your neighbor, child or spouse.
Now, let’s run the machine again. This time however, the chemicals will be provided by your own body. So you turn on the machine. It records all the information needed to make the copy. This time, however, rather than pulling the chemicals from a box, it tears you down (Picture a blender that grinds you up into your atomic constituents) and uses your chemicals—like the transporter on Star Trek, to build the copy and places it facing north again. Let’s just say you were disassembled an hour. Nothing has changed from the first example, except there is only one person left standing. But the irony is, the you that was there last time and facing south, is gone! Just as before, the consciousness of the person left standing facing north is not your own. The copy, believes in every way that they are still the same old you, however knows it is not because of the direction it is left standing. Of course your husband could not tell the difference. Your co-workers would see the same person. Your sisters in Relief Society can see you are gone. But you are, just like last time in the first scenario. That person “that was looking out the window of your mind” a moment ago is gone.
How could you fix the machine to keep the same you there? What if it took you apart and put the doppelganger back together very quickly? Would that make a difference? Rather than constructing the north-facing person from your chemicals in an hour (a long time to be a dead pile of chemicals) what if it only took two minutes? How about twenty seconds. What if it took one micro second? A billionth of a microsecond? Given that it is always a copy, it seems no amount of time would allow the reconstruction to let that original subjective person stay “looking out the window” it is always a new being. (This has terrible implications for Star Trek. It means that every time someone beams to the surface, a new subjectivity is created and an old one lost, but since no one can ever tell the difference, it never gets noticed).
What then is being lost? Me! My existence is lost. From third-person perspectives the same person would be there, but from my perspective the only thing that matters is gone. This shows that something primary and fundamental is being lost. But wait. By hypothesis, that person there is you. It’s made of the same chemicals? But as the first case suggests, it is not you. An identical copy, made of the exact same atoms is not you. Seems like physicalism gets into trouble somewhere. There is something fundamentally different from mind and body even under the assumption of complete naturalism.
In the experiment above, even if the change from original to copy happens almost instantaneously, using all the same components (atoms) as were there before, something is lost (because no mater how fast this copy is made from a different box of chemicals in the first case , the North facing copy is not you). And the thing that is lost is the most valuable part of the biological machine, the subjectively experiencing self. As far as your family, neighbor and peers are concerned, there is no difference. Life goes on with the same old you. But for you, the original existing subjectivity, the you that was looking out the window of the Cartesian Theater (if I may be so gauche), the only you that really matters to you, there is all the difference in the world: the difference between existing and not!
The conclusion seems to be physicalism cannot be right. The mind must be something other than the atoms that make it up–even under the assumption of physicalism. I’m thinking of publishing this so how will they answer? (I know one answer they will make, but it seems fairly unsavory, I won’t say what it is, until you’ve had a chance to think about this a few days–if no one comes up with it.)
[This may take a couple of reads to parse, the key is seeing that the North facing person in the two analogous cases presented are the same, and are not you. The first case this is important because it makes it obvious that it is not you because you are still around]
McGinn C. 1999. The Mysterious Flame: Conscious Minds in a Material World. Basic Books, New York.