FROM ROBERT LAWRENCE KUHN, HOST AND CREATOR OF CLOSER TO TRUTH: What are we? What’s the relationship between the thoughts in our minds and the brains in our heads? Is mind stuff different from brain stuff? Or is there something special about mental activity that’s not crammed into craniums? Something special that makes us human? Something non-brain? Something nonphysical?
These questions compose the “mind-body problem,” which has enticed philosophers for centuries (and beguiled me for decades) and touches all we know and do as human beings. I thought that getting a doctorate in brain research would help me figure it out. I’m not sure it did.
To frame the mind-body problem, I start with John Searle, a renowned philosopher of mind at the University of California, Berkeley. Searle critiques both standard solutions—materialism (all thought is reduced to brain) and dualism (mind is totally different from brain). He says both materialism and dualism are “trying to say something true—it’s just that they both end up saying something false. And the trick is to try to preserve the true part .... The materialist says, ‘Reality is ultimately physical particles and fields of force.’ That’s right. But then the materialist denies the irreducibility and existence of the mental. The dualist grants the irreducibility and existence of the mental, but then says it’s ‘not part of the physical world.’ That’s wrong. Most philosophers are materialists of some kind or another because they just think dualism fails.”
Searle’s position is clear: Consciousness is real and based entirely on the brain, and once we learn enough about the brain, we will know everything about consciousness. I know something about the brain, but I cannot yet imagine how knowing even a whole lot more would explain our inner sense of consciousness.
Ned Block, formerly at the Massachusetts Institute of Technology, now at New York University, draws an analogy: “Consciousness is like water. It has a biological essence. So the mind-body problem for consciousness is one where the question is: What is the biological nature of the mind? The mind-body problem for thought and other aspects of cognition likely turns out to be mainly functional; it’s a matter of how thought, how representations in the mind, function so as to produce thinking.” As to what happened to the postulation of the “Identity” solution—that is, that the mind is wholly equal to the brain—Block states, “The problem is the explanatory gap: how it could be that the neuro basis of a given phenomenal state is the neuro basis of that state as opposed to some other phenomenal state or no state at all. We don’t understand that, and furthermore, we don’t even see how we could understand it.”
With all I know about the brain, I can imagine explaining expressions or outputs of consciousness but never its inner sense or feeling.
Some would say that I’m looking in the wrong direction. Traditionally, almost everyone assumed that human beings had a nonphysical soul. The soul was the real you, a position most philosophers now reject.
Not J.P. Moreland, a Christian philosopher, who claims that the “fundamental questions about the nature of consciousness and whether there is a soul are just not scientific questions; they’re questions like, what is a thought? What is a semantic meaning? There has never been a single discovery in neuroscience or any other branch of science that a dualist—that is, one who believes in a soul—could not easily accommodate within his or her theory.”
Moreland goes on to argue, “There are things true of conscious states that aren’t true of physical states, so they can’t be the same thing. Thoughts are either true or false, but no brain state is either true or false. A thought can’t be located close to my left ear, but the brain state that’s going on while I’m having a thought is located in a region of the brain. The brain state has a shape and a size, but the thought itself doesn’t. Thoughts have internationality—they are about things—but no material state of the brain is about anything. One more example: There is a what-it’s-like to be conscious. There is a what-it’s-like to feel pain, a what-it’s-like to see red. What-it’s-like is not something that can be captured in the language of physics, chemistry, or neuroscience.”
As for the neural correlates of consciousness, Moreland gives this analogy: “Suppose that I were in an automobile and I was trapped in the driver’s seat with a seat belt and I couldn’t get out. My ability to drive around town would depend on whether the car was working; if the car broke down, I wouldn’t be able to move. That wouldn’t prove I was the car. That would simply prove that I am functionally dependent upon the car when I’m in the car. So I think that neural scientific correlations are exactly what the dualists would expect.” Correlation and identity are not the same.
I’d love to see the soul exist, solve the mind-body problem—and get a shot at immortality as a kind of bonus. But if it’s that simple, and that important, why doesn’t everyone get it?
Marvin Minsky certainly doesn’t get it. He’s a pioneer of artificial intelligence and argues quite the opposite: that what we call the mind is entirely the output of the biological machine we call the brain. When I tell Minsky that many believe that there’s something extra, some soul, that we need to introduce or inject to make human consciousness—that we need to marry some sort of a nonphysical thing with a physical thing—he responds with indignation: “That sounds just plain silly because how does a soul help? Unless you tell me what are a soul’s parts and how they work, you haven’t answered anything. All you’ve done is provided a word to keep you from thinking about a hard question. When you think you see ‘redness,’ there isn’t any redness. There’s a very complicated process that goes on in many different parts of the brain when you see red. People who talk about a soul are just people who are too ignorant or unambitious or lazy or faith-ridden—I don’t know what insults to hurl at them ....”
To Colin McGinn, a University of Oxford philosopher teaching in the United States, the mind-body problem is a profound mystery. McGinn is so passionate about the depth of this mystery, he is called a “mysterian.” He claims that consciousness “has a nature which makes it really different from the brain .... What is it about the brain which explains why the brain and only the brain gives rise to this phenomenal experience that we call consciousness?”
McGinn rejects brain complexity as a solution for two reasons. “First,” he says, “lots of things are very complex, and yet those things don’t have lower degrees of consciousness. The kidneys are less complex than the brain; do kidneys have a degraded or lower form of consciousness? There’s no reason to think that. So why should the mere number of connections between neurons generate consciousness? We’re moving from one kind of thing to another kind of thing, and complexity doesn’t seem to breach the gap at all .... As far as we can see, within the conceptual scheme that we have now, which has worked so well with the empirical world, nothing removes the mystery.”
Lest there be misunderstanding, McGinn adds quickly, “But that doesn’t lead me to any position which postulates a purpose of the universe or anything of the kind because my explanation for why consciousness is so baffling to us is a resolute naturalistic explanation. It arises from the fact that our own intelligence has been evolved, has evolved as an adaptation, and has the kind of limits that any intelligence or any species on the planet has.”
To me, here’s what’s odd: all these distinguished philosophers, each with a different solution to the mind-body problem. Not just “different.” Radically different! To some, our mind is just our brain. To others, we need a soul. To others still, we don’t even need a brain—any good machine could do. Finally, some say consciousness is such a mystery that it may remain forever so.
Such divergence is not the way of science, especially with increasing knowledge about the brain. What’s going on?
Perhaps this paradox is a type of clue? Perhaps the answer is of a different kind?
The mind-body problem, ages old but perennially new, leads us … closer to truth.

Robert Lawrence Kuhn speaks with John Searle, Ned Block, J.P. Moreland, Marvin Minsky, Alva Noë, and Colin McGinn in "What Is the Mind-Body Problem?" the 20th episode in the Closer to Truth: Cosmos, Consciousness, God TV series, which airs Thursdays on the PBS HD network and many other PBS stations. Every Friday, participants in the series will share their views on the previous day's episode.