Neuroscience & Mind Icon Neuroscience & Mind

What Is Consciousness?

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The most intractable question in modern neuroscience and philosophy of the mind is often phrased “What is consciousness?” The problem has been summed up nicely by philosopher David Chalmers as what he calls the Hard Problem of consciousness: How is it that we are subjects, and not just objects? Chalmers contrasts this hard question with what he calls the Easy Problem of consciousness: What are the neurobiological substrates underlying such things as wakefulness, alertness, attention, arousal, etc. Chalmers doesn’t mean of course that the neurobiology of arousal is easy. He merely means to show that even if we can understand arousal from a neurobiological standpoint, we haven’t yet solved the hard problem: the problem of subjective experience. Why am I an I, and not an it?

Chalmers’s point is a good one, and I think that it has a rather straightforward solution. First, some historical background is necessary.

“What is consciousness?” is a modern question. It wasn’t asked before the 17th century, because no one before Descartes thought that the mind was particularly mysterious. The problem of consciousness was created by moderns.

The scholastic philosophers, following Aristotle and Aquinas, understood the soul as the animating principle of the body. In a human being, the powers of the soul — intellect, will, memory, perception, appetite, and such — were no more mysterious than the other powers of the soul, such as respiration, circulation, etc. Of course, biology in the Middle Ages wasn’t as advanced as it is today, so there was much they didn’t understand about human physiology, but in principle the mind was just another aspect of human biology, not inherently mysterious. In modern parlance, the scholastics saw the mind as the Easy Problem, no more intractable than understanding how breathing or circulation work. Human beings are composites of soul and body, integrated form and matter, like (in Aristotle’s phrase) the shape of wax and the matter of the wax are just different aspects of one thing — the wax itself. The scholastics didn’t believe there was a Hard Problem.

René Descartes in the 17th century created the Hard Problem, out of whole cloth. Descartes cast aside the hylemorphic (matter-form) metaphysics of the scholastics, and replaced it, in his psychology, with substance dualism. Descartes proposed that the mind and the body were separate substances, rather than just two principles inherent to one human being. The body (res extensa) and the soul (res cogitans) were joined, in Cartesian metaphysics, to make a whole person, but he identified the person with the res cogitans (the intellectual substance), and depicted the res extensa (the physical substance) as essentially a machine. After Descartes, a human being was a “ghost in a machine.” His new psychology solved no problems, and created many. How do the soul and the body interact, if they are completely different substances? If the soul is separable from the body, how is the soul to be identified as belonging to one body and not another?

In time, with the rise of metaphysical materialism, Descartes’s res cognita was tossed aside, leaving the physical body — the res extensa — identified with the human being. And of course the mind became a mystery, because the only substrate remaining for the mind — the physical body — was stripped of all mental properties, which were discarded with the res cogitans. If a human being was identified only with his res extensa — with his matter extended in space — then of course it would be impossible to explain subjective experience and other aspects of human thought. In the Cartesian model, modified by materialism, the only aspect of a human being that exists is physical, stripped of all mental properties.

The Hard Problem of consciousness is a self-imposed wound. Descartes split the soul from the body, and materialists tossed out the soul. We are left with the body, stripped of mental properties, which means we are left with the Hard Problem.

Only since the emergence of Cartesian dualism and materialism has the question “What is consciousness?” arisen. Let’s take a closer look at the question, and see how to answer it.

When we ask what consciousness is, we usually mean: How is it that we are subjects and not just objects? By subjects, we mean how is it that we experience things, like taste and pain and touch? How is it that we are aware of things like objects and thoughts? How is it that we are self-aware?

From the materialist perspective, there is no satisfactory explanation for subjective experience. This is because of the corner into which materialists have painted themselves: they (tacitly) accept Descartes’s res extensa/res cogitans metaphysics, and then toss out res cogitans, leaving only res extensa. If mental properties are stripped from human beings, obviously one is at a loss to explain mental properties.

The scholastic hylemorphic perspective presents no problem for subjective experience. Sensation, perception, memory, etc. are powers of the soul — powers of matter organized in a specific way. Notice that the hylemorphist and the physicalist can both do neuroscience. The hylemorphist faces no contradiction in his science. The human being, a composite of matter and form, can be studied just fine with the methods of empirical science. The materialist can’t escape the contradiction in his science. While the materialist does his neuroscience of, say, perception, he must admit (if he’s honest) that his metaphysical perspective provides no explanation for how perception as subjective experience is even possible. Materialist neuroscience is an unending exercise in cognitive dissonance.

In my view, an even more salient question about consciousness than the question of subjective experience is this: How is it that a thought can be about something? After all, objects in themselves aren’t inherently about anything. A tree is just a tree — it’s not about anything. If a thought is merely a process in the brain, how can a thought in the brain be about a tree, which is not in the brain? In philosophical parlance, this “aboutness” goes by the technical name intentionality. Intentionality, in my view, is the essence of what it is to think. What distinguishes thoughts from material things is that thoughts are always about something, whereas material objects are just what they are, without any intrinsic aboutness. German philosopher Franz Brentano in the 19th century said it best: “Intentionality is the hallmark of the mental.”

Intentionality is a catastrophe for the materialist paradigm in neuroscience. Materialists have struggled for a century to explain how a thought in the physical brain can be about something. No materialist explanation has succeeded, nor will one succeed. When materialists stripped res cogitans from res extensa, they were left with mere matter extended in space. The mind becomes inexplicable. No mental acts are explicable in a metaphysical system created by eliminating the mental and leaving only the physical.

Yet the hylemorphist has a straightforward explanation for intentionality. In hylemorphism, the person is a composite of soul and matter. Mental acts are powers inherent to the soul. The soul grasps the form of the object of thought, and comes to contain the form of the object without actually becoming the object. When you perceive a tree, the form of the tree is grasped by the form of your mind. Aristotle noted the profound implication of this insight: “the soul is in a way all existing things…” (De Anima III.8). We contain the form of that which we perceive and understand. What we understand becomes, in a way, a part of us. Intentionality is explained easily and naturally by hylemorphism.

So the question “What is consciousness?” refers to a problem that we moderns have created. It is a problem created by our metaphysics — our Cartesian and materialist metaphysics — and it was created by our abandonment of Aristotelian and Thomist hylemorphic metaphysics. We can only answer the question correctly — consciousness is several powers of the human soul, the hallmark of which is intentionality — by returning to the scholastic hylemorphic understanding of nature and of the human person.

Image: Portrait of René Descartes, after Frans Hals, via Wikicommons.

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.