A TV show about space exploration has a problem at the outset. You want your crew to be able to get off the starship occasionally and visit planets (which look a lot like LA backlots). Do they have to go through the tiresome and expensive to produce procedure of getting into a shuttlecraft, flying to the planet surface, landing, getting out, etc? Reversing it all to go back up to the starship? Gene Roddenberry had an inspired and elegant solution: the transporter.
The real transporter puzzle is whether the person who goes into the transporter is the same one who comes out. But first, a more basic question, one that has tormented western civilization for half a century, and which Sean Carroll takes up at the start of his book The Big Picture.
How does the transporter on Star Trek work?
Does it “disassemble you one atom at a time, zip those atoms elsewhere, and then reassemble them?” (Carroll p. 15) Or does it “send only a blueprint of you, the information contained in your arrangement of atoms, and then reconstruct you” from local materials? Carroll thinks that the crew on the Enterprise usually talked as if your actual atoms were sent to and from the planet’s surface. However, he cites an episode where a transporter glitch created two Captain Kirks, which wouldn’t make sense if it uses only Kirk’s original atoms. There wouldn’t be enough atoms available to build two Kirks. Lawrence Krauss in The Physics of Star Trek, “The Star Trek writers seem never to have got it exactly clear what they want the transporter to do. Does the transporter send the atoms and the bits, or just the bits?” (p. 68)
Which version of the transporter is more logical? The “original atoms” version comports with our idea that the person himself goes to the planet, that this is transportation of a body, and that what materializes on the planet is the very same person who was on the Enterprise a moment earlier. The “original atoms” transporter is like traveling to the planet surface in a shuttle launched from the Enterprise in that your body makes the trip. The “local materials” transporter might seem more efficient. The blueprint of you has to be sent in both versions. One carbon or hydrogen atom is as good as another; nothing special about the ones in Kirk’s body. Why not just use what’s handy down on the planet? One problem would be that if planetary carbon and hydrogen are to be used to build Kirk, what happens to Kirk’s original atoms on board the Enterprise after he disappears? Stored pending his return?
As far as Kirk’s identity at the other end is concerned, it shouldn’t matter whether the transporter uses original atoms or local materials. Carroll: “Using different atoms doesn’t really matter; in actual human bodies, our atoms are lost and replaced all the time.” p.15-16.
The background philosophical assumption is that a person is nothing more than an arrangement of atoms. If the transporter reconstructs Kirk perfectly, atom for atom, that will be Kirk. All of Kirk’s thoughts, feelings and memories go along automatically. No need to transport Kirk’s soul or self separately, because there isn’t any. An exact duplicate of your physical body would also duplicate all aspects of your psychology—conscious and unconscious.
One important point of clarification about identity. It comes in two varieties. Type identity and token identity. Type identity is what we mean when we say all the copies of a book are identical—different objects, all indistinguishable. Token identity refers to an individual object carving a unique path through space-time. That’s your book you put in your backpack this morning. Your property rights attach only to that individual book, even if someone else’s new copy is just as good, since it’s type identical. Often this distinction is referred to as qualitative vs. numerical identity. (e.g. Derek Parfit, Reasons and Persons p. 200) Maybe after you carry your book around in your backpack, it gets beaten up. Then it is no longer type identical to other copies of the book or to the itself when it was new. It remains, however, token identical to the book you’ve owned all along.
When we talk about the identity of people, we mean token identity. Is Clark Kent identical to Superman? We thought they were two separate people, turns out to be the same guy. Clark Kent and Superman are token identical but not type identical.
The main transporter problem is this: when Kirk beams down to the planet, is the body on the planet token identical to the Kirk who was on the Enterprise, or only type identical? Does the transporter destroy Kirk and build a new one each time?