There’s a sort of creature invented by philosophers called philosopher’s zombie or a p-zombie for short. The p-zombie, unlike say the movies featured in movies by George Romero (may he rest in peace), are not shambling, stupid, re-animated corpses. Rather, they’re people just like you or me except in one respect: they are completely unconscious. They have no inner life, no feelings, no memories, no imaginations, none of that. But in spite of not having an inner life, they are behaviorally identical to people who do have inner lives. Poke one with a pin and it will say “ouch” and act indignant with you, as if it were really feeling pain. Ask a p-zombie about a sad incident in its childhood and it may be able to do so, perhaps with tears in its eyes. But it is not “remembering” its childhood anymore than a record player is “remembering” the contents of a disk it is playing, and it is not sad any more than a classically-trained actor playing Lear is actually mourning Cordelia.
You can’t tell a p-zombie from a “real” person by observing what it does, because what it does is the same thing a as “real” person. More unsettling than that, you can’t somehow peer inside someone and tell whether or not they are a “real” person or a p-zombie. Look inside a “real” person’s brain, and all you will see are a bunch of cells squirting electrochemical signals at one another. A p-zombie’s brain is just the same way. In neither case can you observe a “mind,” see a “person,” or observe “feelings.” To be sure, you might come to confident that certain brain-states correlate reliably with states of mind. You might, for example, come to believe based on evidence from a long series of tests that a certain neuronal firing pattern is someone thinking of a white bear. But this again is only correlations of observed behaviors: when the state is observed, the subject reports thinking of a white bear. The problem is that p-zombies just as readily as “real” people can report thinking of a white bear. It’s just that the p-zombie is not really thinking of anything at all, while the “real” person is. In neither case do you actually see something inside the head that looks like a white bear, or directly observe the White Bear State of Mind.
Most philosophers think that p-zombies are physically impossible and can’t exist in our world, and at least some think that they are metaphysically impossible, that is, that they can’t exist in any possible world. One has to admit that the p-zombie is a pretty unsettling concept. Anyone you know could (in theory, anyway) be not a person, but a p-zombie. Your boss. Your parents. Your spouse. Your adorable toddler daughter who says “I wuv you” as she drifts off to sleep in your arms might not love you at all, but just be a piece of machinery carrying out its programming, unfeeling as any rock.
The concept of the p-zombie makes an interesting thought experiment possible. Suppose there were a drug that could turn you, permanently, instantly, and irrevocably into a p-zombie. Upon taking a does of the drug your consciousness would be instantly annihilated and gone for good. But no one would ever actually be able to tell that you had taken the drug. Future history will be exactly the same as if you had not done so, because the p-zombie that was you will behave exactly as you would have behaved. It will continue to get up in the morning, catch the train to work, stand around the watercooler with colleagues griping about the boss, come home in the evenings, help its children with their homework, have increasingly dutiful and diminishingly frequent sex with your spouse, age, retire, move to the Sunbelt, collect various government benefits, and die, just like you would have. Through all of this, “you” will be gone, together with all the joys and sufferings the balance of your life might contain. The p-zombie will act happy or sad or angry, happy at your daughter’s wedding or angry during its periodic quarrels with your spouse. But it just as much as you will live in the blessed calm of complete consciousness.
Thus p-zombification might be thought of not so much as a kind as an alternative to suicide, and leads me to wonder whether if it were somehow available, it wouldn’t cut off a slice both of suicides and non-suicides. I should think it would do both, and my reason for thinking so is at least in part autobiographical. At the closest I ever personally came to suicide, around the age of thirty or so, the thought that stayed my hand more than any other was that of the suffering that my killing myself would inflict on people I loved, most particularly on my parents (ironic for an antinatalist to feel that way perhaps, but emotional life is messy). I can’t really guarantee that things would have been the same had there been a way out of suffering that they and no one else need ever have known about.
I think I find myself — though no philosopher — in the “metaphysically impossible” camp. Indeed, the very concept of the p-zombie reminds me of the old classicists’ joke about discovering that The Odyssey was not actually written by Homer, but by another man with the same name.
I am aware that consciousness itself is a sometimes-disputed concept, but I feel as if the p-zombie notion embeds within itself the belief in consciousness as existing distinct from behavior. My intuition tells me that thinking of a white bear and acting in every respect as if I think of a white bear might be two sides of the same unsplittable coin. If consciousness is anything, it’s an emergent property of the scandalously-awful program running badly on my meat, and the meat always *twitches* during execution. Phrasing it less organically, he physical manifestations of the running program (the things the world can observe about me) seem likelier-than-not to be inextricable parts of the program’s execution. The fact that I can be observed acting as if I think of a white bear is the highest, nay the *only*, evidence we have that, in that moment, I am a thinking being at all. To say that I can still be thus observed, but postulate (even as a thought experiment) that there’s nobody home inside? It may be the same sort of Carrollian nonsense as saying that my foot is executing a high kick but my ankle and leg are not moving, when in reality if they aren’t moving together then nothing at all is happening in the kicking department. Bad news for a weary leg; you don’t get to stay home from the kicking party. There *is* no kicking party without you.
At first blush this seems not to reach the thought experiment. “Yes, yes, of course, but move past that; imagine that there *was* a drug that made it possible.” And yet I find that I cannot so imagine. I do not think the p-zombie trick is possible; and so the invitation to essay the thought experiment reminds me of (has to me the emotional flavor of) various too-familiar appeals to religion. “It’s easy,” they say. “Merely have faith, and the vast wonders of the Lord’s grace will flow into your heart.” But the words “have faith” have always seemed to me to be Corrollian nonsense, the same as our high-kicking man with the motionless leg or the conscious-acting p-zombie with no consciousness. To me they all parse like Alice’s exhortation to believe impossible things before breakfast. Which would be very fine if I had the knack, but instead it puts my brain into a halting state beyond which it (or me, if there’s a distinction) is unwilling or unable to progress.
Upon re-reading I feel the need to elaborate on my notion of nonsense. “Imagine that you are a pink elephant” is nonsense, but it’s perfectly functional nonsense. I can do that, and I can pretend (within the limits of physicality and my acting ability) to act as a pink elephant might, even though there’s no actual way for me to actually *be* a pink elephant. No, my argument is that the p-zombie notion is a higher-order nonsense: “Imagine a square circle.” Squares and circles don’t work like that; the exhortation itself is broken upon utterance. “Have faith in the Lord” is broken nonsense of the same sort, or so it has always seemed to me; and the purpose of these comments is to explain why the p-zombie thought experiment strikes me as similarly challenged.
Strangely, I find it quite easy (or so it seems to me, anyway) to imagine an absence of consciousness combined with apparent intelligent responses to the world. Start with something very simple — you might recall a very simple computer program called ELIZA which would respond to cues in natural language to carry on a “conversation” with a user, which at least some users found rather immersive. But no one actually thought that when ELIZA “asked” a user to “tell me more about your mother” that there was any consciousness curious about your family living inside your TRS-80. Some philosophical thought experiments in effect scale up from ELIZA to argue for far more sophisticated kinds of non-conscious intelligence — think of John Searle’s famous Chinese room thought experiment. Most people would think that the Chinese room isn’t conscious either, even if it can carry on genuinely human-level conversation with another (Chinese speaking!) human. From another perspective, my old teacher Derek Parfit (may he rest in peace and fuck you, year 2017) often argued that consciousness might be a superfluous phenomenon — one we could easily imagine the world being without, using the known psychological phenomenon of blindsight as an example of how this might work: if people can respond to visual stimuli while reporting no conscious experiences of them, why not extend our imaginations all the way to the complete elimination of consciousness?
One possible test of whether we can “imagine” something might be whether we can write a coherent story about them. It’s probably hard for p-zombies, but arguably this has been done by the hard sci-fi writer Peter Watts in his novel Blindsight, the full text of which is available for free here.
There’s also a larger question about the relevance of the “possibility” of a premise when the point of a thought experiment is not to try to elicit not a physical or logical intuition but a value judgment, which is why I’m interested in the p-zombie. Consider a simpler example: suppose that someone asked you to imagine having a time machine and asked you where and when you might use it to visit. Now I don’t know your views about time-travel, but it would certainly be respectable of you to see it as physically impossible and perhaps even logically impossible (all those ugly paradoxes about cuckolding your great-grandfather have to be avoided somehow!). But even if you had such views, it would seem sort of strange to say that you couldn’t come up with an answer to the question (and of course, “I like it fine right here and now, thanks” is a perfectly respectable, if unadventurous, answer to the question) on the basis of the fact that you just don’t get how there could be time travel.