The Zombic Hunch

The Zombic Hunch

Most people have a hunch—it’s no better than that, really—that no robot (made of silicon and metal and plastic, etc.) could ever be conscious the way we humans are. There is something about our living, breathing, organic bodies and brains that is necessary for consciousness. This is an intuition that hardly needs pumping, so ubiquitous is it, and maybe these people are right. But if our bodies and brains can themselves be seen as made of robots made of robots made of robots, and so on, all the way down to below the neuron level where the motor proteins and other nanobots trudge along making the whole system work, we can see that maybe that hunch is just an artifact of impoverished imagination: folks have been thinking about robots that are too simple, by many orders of magnitude. A friend once responded to this opening gambit of mine by trying to nip it in the bud: “I just can’t conceive of a conscious robot!” Nonsense, I replied. What you mean is that you won’t conceive of a conscious robot. You think it is silly and preposterous to try to take the idea seriously. But it’s actually child’s play to conceive of a conscious robot, or, for that matter, a conscious choo-choo train (The Little Engine That Could) or a conscious Christmas tree (all those sappy children’s stories about lonely little fir trees that pine for a home). Anybody who has seen Star Wars has spent an hour or so conceiving of R2D2 and C3PO as conscious. We have done this since we were children, “without a second thought” for the most part. It’s not just easy, it’s almost irresistible when we are confronted with something that acts—and especially, talks—like a human being.

Here’s an interesting fact: since the pioneering work of neuroscientist Wilder Penfield in Montreal back in the 1950s, there have been many operations that exposed the brains of wide-awake patients who were able to say what it was like when their brains were stimulated there or just there. I don’t think any participant or observer of one of these operations has ever thought, “Oh my gosh! This isn’t a person. This is a zombie. It has to be, because when we look inside, all we find is gray matter.” No, it is just too obvious—look! listen!—that the patient is conscious. And it would be just as obvious, really, if we were to open up somebody’s skull while he or she is conversing with us and find the cranial cavity packed with microchips. We’d learn, perhaps to our surprise, that a conscious robot was not just easy to conceive of or imagine, but actual.

Some philosophers think that your imagination would be playing a trick on you if you fell for this “merely behavioral” evidence of consciousness and jumped to that conclusion. “Don’t fall, don’t jump!” might be their motto. Proving that another person is conscious is much harder than that, since that person might—it’s at least a logical possibility—be a “zombie.” Not a voodoo-style zombie of the sort that one sees in movies or dresses up as at Halloween. The walking dead are readily distinguishable from normal people by their behavior (and their horrible appearance). Philosophers’ zombies, in contrast, can be delightful company, the life of the party, as loving and joyous and spontaneous as anybody you know. Some of your best friends might be zombies. Philosophers’ zombies are (by definition) behaviorally indistinguishable from normal conscious human beings, but “there’s nobody home”—they entirely lack any inner life, any conscious experience. They just appear from the outside to be conscious. If you agree with these philosophers that this is a serious issue, if you wonder—given the logical possibility of philosophers’ zombies—how there could ever be a scientific, materialistic theory of consciousness, then you are gripped by the Zombic Hunch.

Let me acknowledge right away that I can feel the Zombic Hunch as vividly as anyone. When I squint just right, it does sort of seem that consciousness must be something in addition to all the things it does for us and to us, some kind of special private glow or here-I-am-ness that would be absent in any robot, and that is all but unimaginable as a “mere” physical activity of the brain. But I’ve learned not to credit the hunch. I think it is a flat-out mistake, a failure of imagination, not an insight into necessity. Convincing others of this, however, proves to be no easy task, and we will need several different intuition pumps to loosen the grip of the Zombic Hunch.

To start, we may get our bearings on this logical possibility by comparing it with a few others. It is logically possible that you are living in the Matrix, and all of the life you see around you and apparently participate in is a virtual reality show designed to keep you calm as your actual body lies motionless in a high-tech pod of some kind. It is logically possible that there aren’t really any carbon atoms; what appear to scientists to be carbon atoms are actually kazillions of tiny spaceships piloted by aliens whose life work is to pretend that they are carbon atoms. It is logically possible that the entire universe was created about six thousand years ago, with all the so-called fossils in place and photons streaming in as if from galaxies light-years away. (It’s logically possible that the world was created ten minutes ago, complete with all the purported memories of your past installed in your brain.) We may find such logical possibilities amusing premises for fiction, but we don’t take them seriously as signs that our physics and chemistry and biology need to be overhauled or abandoned. Is there anything that makes the Zombic Hunch more substantial, more worthy of consideration? Many serious thinkers have thought so.

Perhaps the grandfather of all intuition pumps designed to yield something like the Zombic Hunch was invented hundreds of years ago by Gottfried Wilhelm Leibniz, the philosopher/mathematician who shares credit with Isaac Newton for inventing calculus. He was as smart and ingenious as any thinker in his age, and yet he fell for this intuition pump of his own devising.

And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception. Thus [my italics] it is in a simple substance, and not in a compound or in a machine, that perception must be sought for. [Leibniz, 1714, para. 17]

This “Thus” is one of the most glaring non sequiturs in all of philosophy. Leibniz doesn’t give us any intervening argument for the conclusion; he thinks it is too obvious to need any. Consider William Bateson, the early-twentieth-century geneticist who couldn’t imagine that genes could be material entities (see p. 100 of the source). Just as Bateson had no way of taking seriously the extravagant idea of three-billion base-pairs in a double helix inside every cell (preposterous!), Leibniz had no way of taking seriously the idea of a “mill” with trillions of moving parts. He would insist, no doubt, that “just adding more parts” couldn’t take you from machinery to mind, but that would be only his hunch, not anything he could claim to demonstrate. But if Darwin, Crick, and Watson have exposed Bateson’s failure of imagination, Turing has rendered Leibniz’s intuition pump obsolete. Except that he hasn’t. Not yet. In due course, I think, the Zombic Hunch will fade into history, a curious relic of our spirit-haunted past, but I doubt that it will ever go extinct. It will not survive in its current, mind-besotting form, but it will survive as a less virulent mutation, still psychologically powerful but stripped of authority. We’ve seen this happen before. It still seems as if the earth stands still and the sun and moon go around it, but we have learned that it is wise to disregard this as mere appearance. It still seems as if there’s a difference between a thing at absolute rest and a thing that is merely not accelerating within an inertial frame, but we have learned not to trust this feeling. I anticipate a day when philosophers and scientists and laypeople will chuckle over the fossil traces of our earlier bafflement about consciousness: “It still seems as if these mechanistic theories of consciousness leave something out, but of course we now understand that that’s an illusion. They do, in fact, explain everything about consciousness that needs explanation.”

I think the Zombic Hunch is also fostered by thought experiments such as John Searle’s Chinese Room, the inspiration for my coinage, “intuition pump.”

Footnote: One reader of an early draft of this book thought I was making all of this up. If you share that suspicion, check out the long, deadly serious article on philosophical zombies in the august Stanford Encyclopedia of Philosophy, online at http://plato.stanford.edu/entries/zombies/.