I Am a Strange Loop

with my commentary on Parfit’s provocative tale (and also, of course, on Dan’s, thanks to the referential power of analogy).

The Murky Whereabouts of Cartesian Egos

The key question raised by Parfit’s tale is this: “Where is space voyager Derek Parfit really, after the teletransportation has taken place in Episode II?” Put otherwise, which of the two claimants to being Parfit really is Parfit? In Episode I, Parfit the storyteller plants a most plausible-seeming answer, but then in Episode II he just as plausibly undermines that answer. At this point, you can probably almost hear Strange Loop #642 intensely identifying with the space traveler and screaming out, “Which of the two would I be?”

To my mind, one cannot claim to have said anything significant about the riddle of consciousness if one cannot propose (and defend) some sort of answer to this extremely natural-seeming and burning question. I think that by now you know my answer to the question, but maybe not. In any case, I’ll let you ponder the issue for a moment, and meanwhile, I’ll go on to tell you more or less how Parfit sees the matter.

This issue lies at the very core of Parfit’s book, and the explanation of his position occupies about a hundred pages. The key notion to which he is opposed is what he dubs “Cartesian Pure Ego”, or “Cartesian Ego”, for short. To put it in my words, a Cartesian Ego constitutes one exact quantum of pure soul (also known as “personal identity”), and it is 100 percent indivisible and undilutable. In short, it is what makes you be you and me be me. My Cartesian Ego is mine and no one else’s, has been from birth and will be to death, and that’s that. It’s my very own, completely private, unshared and unsharable, first-person world. It’s the subject of my experiences. It’s my totally unique inner light. You know what I mean!

I have to admit, parenthetically, that every time I see the phrase “Cartesian Ego”, although my eyes perceive only one “g” there, some part of me invariably hallucinates another “g”, and the image of an egg bubbles up in my brain — a “Cartesian Eggo”, if you’ll permit — a beautifully formed egg with a pristine white shell protecting a perfectly spherical and infinitely precious yolk at its core. In my strange distorted imagery, that yolk is the secret of human identity — and alas, Parfit’s central mission in his book is to mercilessly crush the whole egg, and with it, the sacred yolk!

There are two questions that Parfit does his best to answer. The first one is: When Parfit is teleported to Mars in Episode I, is his Cartesian Ego teleported along with him, or is it destroyed along with his body? The second question, seemingly even more urgent and confusing, is this: When Parfit is teleported to Mars in Episode II, where does his Cartesian Ego go? Could it possibly go to Mars, abandoning him on Earth? In that case, who is it that remains on Earth? Or conversely, does Parfit’s Cartesian Ego simply stay put on Earth? In that case, who, if anyone, is it that debarks from the cubicle on Mars? (Note that we are conflating the word “who” or the phrase “who it is” with the notion of a specific, uniquely identifiable Cartesian Ego.) The temptation to ask such questions (and to believe that these questions have objectively correct answers) is nearly irresistible, but nonetheless, the nearly universal intuitions that give rise to this temptation are what Parfit is out to crush in his book.

To be more specific, Parfit staunchly resists the idea that the concept of “personal identity” makes sense. To be sure, it makes sense in the everyday world that we inhabit — a world without telecloning or fanciful cut- andpaste operations on brains and minds. The fact is, we all more or less take for granted this notion of “Cartesian Ego” in our daily lives; it is built into our common sense, into our languages, and into our cultural backgrounds as profoundly, as tacitly, as seamlessly, and as invisibly as is the notion that time passes or the notion that things that move preserve their identity. But Parfit is concerned with investigating how well this primordial notion of Cartesian Egos stands up under extreme and unprecedented pressures. As a careful thinker, he is doing something analogous to what Einstein did when he imagined himself moving at or near the speed of light — he is pushing the limits of classical notions — and, like Einstein, he finds that classical worldviews do not always work in worlds that are very different from those in which they were born and grew.

Am I on Venus, or Am I on Mars?

In his hundred or so pages of musings on this issue, Parfit analyzes many thought experiments, some dreamt up by himself and some by other contemporary philosophers, and his analysis is always keen and clear. I have no intention to reproduce here those thought experiments or his analyses, but I will summarize what his conclusions are. The essence of his position is that when pushed to its limits, personal identity becomes an indeterminate notion. In extreme circumstances such as Episode II, the question “Which one of them am I?” has no valid answer.

This will be extremely unsatisfying and unsettling to many readers of Parfit’s book, and to many readers of this book, as well. Our intuitions as we grew up on planet Earth have not prepared us for anything in the least like a nondestructive teleportation scenario, and so we clamor for a simple, straightforward answer, yet somehow we also intuit that none will be forthcoming. After all, we could invent Episode III, featuring a destructive teleportation scenario as in Episode I, but with signals simultaneously sent out to receiving stations on Venus and on Mars. In this scenario, shortly after the destruction of the original Parfit body and brain, two brand-new Parfits (both complete with shaving nick) would be assembled more or less simultaneously on the two planets, and now there really doesn’t seem to be any valid claim of primacy for either one above the other (unless you argue that the first one finished should get to claim the honor of the Cartesian Ego, but in that case, we can simply posit that they are assembled in synchrony, thus barring that easy escape route).

To our everyday, downhome, SL #642–style minds, it’s very stark and very simple: one of the Parfits is a fake. We cannot imagine being in two places at once, so we think (identifying ourselves with the intrepid voyager), “Either I’ve got to be the Venus one, or the Mars one, or neither one.” And yet none of these answers is in the least satisfying to our classical intuitions.

Parfit’s own answer is actually closer to the thought that I brusquely dismissed in the previous paragraph: that we are in two places at once! I say it’s closer to that answer rather than saying that it is that answer, because Parfit’s view, like mine in this book, is that these things that seem so black-and white to us actually come in shades of gray — it’s just that in ordinary circumstances, things are always so close to being pure black or white that any hints of grayness remain hidden from view, not only thanks to the obvious external fact that we all have separate physical brains housed in separate skulls, but also thanks to an extensive web of linguistic and cultural conventions that collectively and subliminally insist that we each are exactly one person (this is the “caged-bird metaphor” of Chapter 18, and it’s also the Cartesian Ego notion), and which implicitly discourage us from imagining any kind of blending, overlapping, or sharing of souls.

There is also, I cannot deny it, an absolute certainty, deep down in each one of us, that I cannot be in two places at once. In earlier chapters, I went to great lengths to give counterexamples of many sorts to this idea, and Parfit, too, takes great pains to give other kinds of evidence about the possibility of spread- out identity. In fact, he eschews the term “personal identity”, preferring to replace it by a different term, one less likely to conjure up images of indivisible “soul quanta” (analogous to unique factory-issued serial numbers or government-issued identity cards). The term Parfit prefers is “psychological continuity”, by which he means what I would tend to call “psychological similarity”. In other words, although he doesn’t propose anything that would smack of mathematics, Parfit essentially proposes an abstract “distance function” (what mathematicians would call a “metric”) between personalities in “personality space” (or between brains, although at what structural level brains would have to be described in order for this “distance calculation” to take place is never specified, and it is hard to imagine what that level might be).

Using such a mind-to-mind metric, I would be very “close” to the person I was yesterday, slightly less close to the person I was two days ago, and so forth. In other words, although there is a great degree of overlap between the individuals Douglas Hofstadter today and Douglas Hofstadter yesterday, they are not identical. We nonetheless standardly (and reflexively) choose to consider them identical because it is so convenient, so natural, and so easy. It makes life much simpler. This convention allows us to give things (both