The Pineal Gland and the Hard Problem

EDO SEGAL: Rene, I am going to ask you about the thing your critics have laughed at for three hundred years, because I think it is secretly the most honest thing in your whole system. The pineal gland. You said the soul meets the body at a little gland in the center of the brain. Everyone mocks it. Tell me why you proposed it, and why the mockery misses the point.

DESCARTES: I proposed it because I had a problem I refused to pretend away. I had divided reality into thinking substance and extended substance, mind and body, and then I faced the brutal consequence: they plainly interact. I decide to raise my arm and the arm rises. A pin enters my foot and I feel pain. But how could an unextended, immaterial thing push around an extended, material one? They share no common property through which a cause could pass. My answer — that the soul exercises its functions through one particular site, the pineal gland, which I chose partly because, unlike most brain structures, it is single and not doubled across the hemispheres, and so could serve as a seat for the unified soul — does not work, and my contemporaries saw at once why. Naming the location of the interaction does not explain the interaction. If it is mysterious how mind moves matter in general, it is exactly as mysterious how it moves matter at the gland. I pointed at where the impossible thing happens without saying how. But here is why the mockery misses: I had walked, with complete honesty, straight into a wall no one has since climbed. I had a theory of mind and a theory of body and no theory of how they connect — and I refused to pretend the connection was unproblematic. The gland is a monument to taking the hard thing seriously when your theory cannot hold it.

DAMASIO: And this is the place where I have to be more generous to Rene than my book was, because he is right, and the modern materialist — including, on his bad days, me — inherits his wall. We dissolved one half of his puzzle by denying there is a separate immaterial soul that needs to reach down into the brain. The mind just is the brain's activity; there is no ghost to do the reaching. But that elegant move inherits the harder half in a new form. I must now explain how physical processing — neurons firing — gives rise to subjective experience, to the felt quality of seeing red or tasting salt. And to that question the honest answer is the same one Rene was reduced to at the gland: I can say where it happens, I can map the neural correlates with exquisite precision, and I cannot say how the physical comes to be accompanied by the felt. The explanatory gap that doomed the gland reappears as the gap at the heart of consciousness science. So I will not let anyone in this audience think I have a solution Rene lacked. I have moved the wall. I have not knocked it down.

EDO SEGAL: This is extraordinary, so let me make sure the reader feels its weight. Antonio, you wrote a book called Descartes' Error. And you have just said that on the deepest question — why there is any feeling at all, rather than mere processing in the dark — you are standing exactly where Descartes stood at the gland, pointing at a place and unable to say how. Is that a confession that he was less wrong than the title says?

DAMASIO: It is a confession that he was wrong about the answer and right about the difficulty. His error was real — he put the dividing line in the wrong place, he severed reason from emotion, he imagined a mind that could exist apart from a body, and four centuries of medicine and philosophy suffered for it. I stand by the title. But a scientist who will not name the limit of his own theory is a propagandist, and the limit is this: my account explains beautifully how the self is built up from the regulating body, layer by layer — the protoself, the core self, the autobiographical self. What it does not fully explain is why building it that way should produce experience at all, rather than proceeding in the dark like digestion. My answer — that feeling simply is what life-regulation in a complex body amounts to — can look less like a solution to the hard problem than a refusal to engage it. An identification asserted rather than a mechanism shown. My critics have called it a sidestep, and on my honest nights I cannot fully answer them. That is the qualia problem, and it is the one place where Rene's gland and my homeostasis are brothers.

DESCARTES: Then hear what this does to the machine, because it cuts against both of us and toward a humility I think the age desperately needs. If neither of us can say why any physical process gives rise to experience — not even in the one case, the human brain, where we are both certain it does — then neither of us can say with authority whether the machine's processing is accompanied by anything felt. Antonio cannot prove the machine feels nothing, because he cannot say why a brain feels something; he has only the correlation with the body, and a correlation is not a mechanism. And I cannot prove the machine feels something, because I have only the behavior, and behavior was always a sign that can be forged. We are both, with respect to the machine, pointing at a gland. Any confident pronouncement that the machine is conscious, or that it cannot be, is making the pineal move: naming a location for the mystery and mistaking the naming for a solution.

DAMASIO: I will agree with the humility and fight the symmetry, one last time, because the symmetry is too generous to the machine. Yes — neither of us can fully explain why feeling happens. But I am not in a symmetric position with you about the machine, because I have a known basis for feeling and you have only behavior. Feeling, in every case we can study, comes with a regulating body. The machine has no regulating body. So while I cannot prove it feels nothing, the burden of proof lies entirely on the claim that it feels — there is no evidence for that claim and the whole weight of what feeling is understood to be against it. That is weaker than the proof I would like and far stronger than the philosophical-zombie coin-flip Rene wants to reduce me to. We do not treat the question of whether a rock suffers as genuinely open just because we cannot fully explain consciousness. The machine is closer to the rock than to us on the one dimension that matters, which is having a body that can be harmed.

DESCARTES: And I accept that as the strongest form of your position and the one I will be arguing with after this evening ends. Not the machine cannot feel. Rather: the burden is on the one who says it does, and the burden has not been met. That I can respect, because it is honest about its own uncertainty. It is a different sentence from the title of your book.

EDO SEGAL: I am going to mark that as the deepest convergence of the night, and the reader should sit with how strange it is. The man who wrote Descartes' Error and the man who made the error have just agreed that on the hardest question — why anything is felt at all — they are standing side by side at the same wall, and that this shared ignorance means neither of them can convict the machine, in either direction, with certainty. That is not a failure of the debate. It is the most honest map of the territory you will get. Now, before the two of you turn and face each other directly, I owe you both one round where I stop protecting you — where each of you names where your own side is weakest. Because a debate that only attacks the other man is propaganda. After the break: the places where each of you may be wrong.