In science fiction, there was always something I worried about. What are the philosophical implications of a transporter? It turns out, someone worried about that before me, and came up with Swampman.
Don't get me wrong, I love the future, but ever since I started watching Star Trek there was something that worried me. Whenever they used the transporter, I wondered what happened to them. Surely the act of ripping all their molecules apart and reassembling them wasn't the same as popping them on a shuttle craft. Were we watching clone Spocks and Kirks that whole time?
It turns out, that has been considered, and actually has been given an official philosophical name - Swampman. Swampman's a bit low-tech, but the premise is the same. Suppose a man is out hiking in a swamp. A bolt of lightning hits him and disintegrates him. At exactly that moment, across the swamp, another bolt of lightning hits a chunk of organic matter and assembles, molecule for molecule, the same guy. We will call this guy Swampman, and he has all the responses that the man did. He lives the life the man would, and recognizes all the man's friends, and does the work the man would do. Is he the same guy?
According to Donald Davidson, the answer is no. Swampman would not be the person who hiked into the swamp. He would just be a very, very convenient replacement.
But since transporters are meant to reassemble the person they tear apart, down to the molecule, convenience would have nothing to do with it. They would simply kill whoever went into a transporter by disintegrating them, and replace them with an unwitting copy. Makes all those Star Trek episodes (not to mention the movies), kind of dark. No matter how nobly the crew triumphs, each of them is a poor, confused Swampperson who only has days to live, as their next transporter trip will kill them.
[Via Knowing One's Own Mind.]