Mind Matters Natural and Artificial Intelligence News and Analysis
Photo by Julien-Pier Belanger
Photo by Julien-Pier Belanger at Unsplash

Neuroscientist Michael Graziano Should Meet the P-Zombie

To understand consciousness, we need to establish what it is not before we create any more new theories

In 1992, philosopher Daniel Dennett published Consciousness Explained. In it, Dennett explained quite a few things, but not consciousness.

Now Princeton neuroscientist Michael Graziano takes a crack at it in an essay in New Scientist titled “True nature of consciousness: Solving the biggest mystery of your mind.”

Here I offer excerpts from his text, with my comments:

Graziano’s subtitle:

Far from being a mystical “ghost in the machine”, consciousness evolved as a practical mental tool and we could engineer it in a robot using these simple guidelines

Let’s take it bit by bit:

Far from being a mystical “ghost in the machine”, consciousness… [emphasis mine]

“A ghost in a machine”? That was philosopher Gilbert Ryle’s apt synopsis of Descartes’ substance dualism. Few adhere to substance dualism today. It is a metaphysically vacuous view of nature and the interaction problem—the problem of how an immaterial spirit can connect to a material body—remains a crippling flaw. In my view, to be a substance dualist is to misunderstand substance dualism. It’s not a credible perspective although I understand the attraction. It appears (superficially) to refute materialism, which is a laudable task. But that is a misunderstanding as well.

It’s ironic that modern materialism—the ideology to which Graziano subscribes—came from Cartesian dualism. Descartes’ conception of matter was a sharp break from the Aristotelian/scholastic understanding of nature, in which matter is potency and is brought to actuality by form. Descartes cast aside Aristotelian metaphysics—I don’t think he ever really understood it—and defined matter as res extensa—“extended substance”—meaning that matter was that which was extended in space, as opposed to res cogitans—“thinking substance”—which is that which thinks but is not extended in space. Descartes saw man as a composite of two separable substances—matter and spirit (machine and ghost).

In time, philosophers and scientists exorcised Descartes’ ghost (res cogitans), which left them (still mired in Cartesian metaphysics) with only Cartesian matter—res extensa. Modern materialists understand matter as Descartes understood it—stuff extended in space. As you might imagine, “stuff extended in space” is not a promising way to explain the mind. And sure as heck, materialists have failed to explain the mind ever since.

It’s gotten to the point that eliminative materialists have denied that the mind even exists. If there were ever evidence that the mind doesn’t exist, eliminative materialism itself would be that evidence. It’s mindless nonsense.

So the irony is that materialists inherit their metaphysical framework from a particularly unworkable version of dualism. Of course, Graziano understands none of this. But in a limited sense, he is right. Consciousness is not a ghost in a machine. But that is because Cartesian metaphysics is a mistake. And his own metaphysics—materialism—is degenerate Cartesianism.


Far from being a mystical “ghost in the machine”, consciousness… [emphasis mine]

Graziano brings us to a fundamental question: what is consciousness? He states, and we all implicitly agree, that consciousness is subjectivity—the existence of an “I” rather than merely an “it”. This question follows: can science, which is the study of “it” (i.e. third-person things like rocks and bodies and galaxies), explain the first-person — the “I” — nature of consciousness?

A fanciful, but thoughtful, answer to that question is a philosophical challenge called ‘the conceivability of p-zombies’. It’s worth a brief discussion:

A p-zombie (a philosophical zombie, as distinguished from the kind that sells movies) is identical to a human being but has no first-person (subjective) experience. It’s a meat robot, so to speak, that is indistinguishable in behavior from a human being. Thus, my p-zombie would look exactly like me, walk like me, talk like me, write blog posts like me, etc.. It would do exactly as I do but it would not have an “I” like me. It would feel nothing and think nothing. It would have no “I” at all. To borrow a concept from philosopher Thomas Nagel, there would be nothing it is like to be a p-zombie.

I’m not concerned here to argue whether a p-zombie is practically possible but rather whether it is conceptually possible. Specifically, does a p-zombie break any physical laws of science?

If a p-zombie is conceptually possible—that is, if it does not violate any scientific principles—then it is reasonable to conclude that whatever gives us first-person subjective experience must be something that is not physical, as the term is understood scientifically. If p-zombies, who lack consciousness, are conceptually consistent with physical science, then consciousness is something outside the purview of physical science.

Thus, the conceivability of p-zombies is an argument against materialism and for some kind of dualism. This challenge has given rise to some debate, as you might imagine, and prominent philosophers are to be found on both sides.

I think it’s a pretty good argument. P-zombies are conceivable in the sense that they violate no principle established in physical science. It follows then that our consciousness can only be explained by invoking an explanation beyond physical science.

So if one accepts the definition of consciousness as “that which p-zombies lack and humans have”, consciousness isn’t something that science (as it is now) can explain. I think that’s true, but that’s a weak definition of consciousness.

More rigorously, I think consciousness is a set of abilities—sensation, perception, imagination, emotion, and (for man) intellect and will. This is the Aristotelian/Thomistic view, although I suspect Aristotle would say that “what is consciousness?” is a vague question to start with.

All of these abilities—sensation, perception, imagination, emotion, intellect and will—are powers of the soul. They are specifically powers of the souls of animals (except for intellect and will, which are powers of the souls of humans.)

So Aristotle would say that “consciousness” is the state of having a soul, which is the form of a living thing. That’s a pretty good definition of consciousness, I think. But that gets us into some real metaphysics, which is clearly not territory into which Graziano (or any materialist) ventures.

Well, we didn’t even get past Graziano’s subtitle yet. There a lot more to say about his theory but that is for future posts.

Here is a selection of Dr. Egnor’s articles on consciousness:

In one sense, consciousness IS an illusion. We have no knowledge of the processes of our consciousness, only of the objects of its attention, whether they are physical, emotional, or abstract

Does Your Brain Construct Your Conscious Reality? Part I A reply to computational neuroscientist Anil Seth’s recent TED talk


Does Your Brain Construct Your Conscious Reality? Part II In a word, no. Your brain doesn’t “think”; YOU think, using your brain

Michael Egnor

Senior Fellow, Center for Natural & Artificial Intelligence
Michael R. Egnor, MD, is a Professor of Neurosurgery and Pediatrics at State University of New York, Stony Brook, has served as the Director of Pediatric Neurosurgery, and award-winning brain surgeon. He was named one of New York’s best doctors by the New York Magazine in 2005. He received his medical education at Columbia University College of Physicians and Surgeons and completed his residency at Jackson Memorial Hospital. His research on hydrocephalus has been published in journals including Journal of Neurosurgery, Pediatrics, and Cerebrospinal Fluid Research. He is on the Scientific Advisory Board of the Hydrocephalus Association in the United States and has lectured extensively throughout the United States and Europe.

Neuroscientist Michael Graziano Should Meet the P-Zombie