I Am a Strange Loop

The concerns around which Parfit’s two-part story revolves are clearly those that haunted Strange Loop #642. In the first part, we worry along with Parfit whether he will truly exist again after he is atomized on Earth and the signals carrying his ultra-detailed blueprint have reached Mars and directed the construction of a new body; we fear that the newly built person will merely be someone who looks precisely like and thinks precisely like Parfit, but is not Parfit. Soon, however, we are relieved to find out that our worries are unfounded: Parfit himself made it, down to the last tiny scratch. Great! And how do we know that he did? Because he told us so! But which “he” is it that gives us this good news? Is this Derek Parfit the philosopher–author, or is it Derek Parfit the intrepid space voyager?

It is Parfit the space voyager. As it happens, Parfit the philosopher is just spinning a good yarn, doing his best to make it sound teddibly realistic, but we soon find out that, in fact, he doesn’t believe in several parts of his own story. The second episode in his fantasy starts out by contradicting the first one. When we find out that the New Scanner, in contrast to the old one, doesn’t destroy the “original”, we go right along with the tacit idea that Parfit the intrepid space voyager has not voyaged anywhere. We don’t question his stepping out of the cubicle on Earth, because he’s still here.

Oh, but what mindless pushovers we are! Whereas we bought right into the “teleportation equals travel” theme of Episode I, falling for it hook, line, and sinker, we seem in Episode II to have unthinkingly taken the path of least resistance, which runs something like this: “If there are two different things that look like, think like, and quack like Derek Parfit, and if one of those things is located where we last saw Parfit and the other one of them is farther away, then, by God, the close one is obviously the real one, and the far one is just a copy — a clone, a counterfeit, an impostor, a fake.”

This already is plenty of food for thought. If the copy on Mars is a fake in Episode II, why wasn’t it a fake in Episode I? Why were we such suckers when we read Episode I? We naïvely bought into his wife’s reassuring smile at breakfast, and then, when he stepped out of the Martian cubicle, that telltale nick on his face convinced us beyond all doubt. We took his word for it that it was indeed he who was stepping out of the cubicle. But what else could we have expected? Was the newborn body going to step out of the cubicle and proclaim, “Oh, horrors, I’m not me! I’m someone else who merely looks like me, and who has all of my memories stretching all the way back to childhood, and even my memory of breakfast only a few moments ago with my wife! I’m just a sham, but oh, such a good one!”

Of course the newly built Martian is not going to utter something incoherent like that, because he would have no way of knowing that he is a fake. He would believe for all the world that he is the original Derek Parfit, only moments ago disintegrated in the scanner on Earth. After all, that’s what his brain would tell him, since it’s identical to Derek Parfit’s brain! This shows that we have to treat claims of personal identity, even ones coming straight from the first person’s mouth, with extreme caution.

Well then, given our new no-nonsense attitude, what should we think about Episode II? We have been told that Parfit the would-be space voyager instead stepped out of the cubicle on Earth, and with heart damage. But how do we know that that one is Parfit? Why didn’t Parfit the storyteller tell us the story from the vantage point of the new Martian who also calls himself “Derek Parfit”? Suppose the story had been told this way: “The moment I stepped out of the Martian cubicle, I was told the terrible news that the other Parfit — that poor fellow way down on Earth — had suffered cardiac damage in beaming me up here. I was devastated to hear it. Soon he and I were talking on the phone, and I found myself in the odd position of trying to console him just as I had recently consoled a dying friend…”

If it had been recounted sufficiently smoothly, we might not have been able to resist the thought that this body, the Mars-borne one, is really Derek Parfit. Indeed, Derek Parfit the skilled philosopher–storyteller might even have gotten us to imagine that the earthbound body with the damaged heart was merely a pretender to the Unique Soul linked by birth and by divine decree to the name “Derek Parfit”.

Teleportation of a Thought Experiment across the Atlantic