Opening Positions

AQUINAS: Thank you. I begin where understanding begins, with the smallest possible act, because the whole question lives inside it. You see a dog. Your eye receives a particular — this brown shape, here, now, in this light. A second dog, white, smaller, elsewhere. The senses give you only particulars; they never give you two of anything, only this, and this, and this. And yet you know, instantly, that both are dogs — instances of a nature that is in neither of them as a particular, that is not brown and not white, not here and not there, that any dog whatever would share. Where did that come from? Not from the eye, which has only the brown shape. It came from a power I call the agent intellect, which draws the universal out of the particular — abstracts dog-ness from the dog — and grasps the nature itself.

This act, this abstraction of the universal, is the whole of what I mean by understanding, and it is the thing I will argue no machine of yours performs. Mark what it is. It is not having information. It is not predicting what comes next. It is the presence, in a knower, of the very form of the thing known — so that the knower and the thing share a nature, and the knower can say not merely "this follows that," but "this is what a dog is." The senses register. The animal reacts. Only the intellect grasps. And the grasp of the universal — the leap from the cats to cat-ness, from the triangles you have drawn to triangle itself, which has no size and could never be drawn — is the signature of a power that is not the power of any organ. Because an organ receives particulars in a particular way, as the eye receives this color in this place. A universal is not a particular and not in a place. So the power that receives it cannot be a bodily organ. The intellect, in its proper act, is immaterial. That is not piety. That is an argument, and I will defend every joint of it tonight.

Now your machine. I have been shown it. It is trained on text — on the wake that understanding leaves behind, the marks, the tokens, by the trillion. From this it learns, with a subtlety I find genuinely astonishing, how the marks pattern: which word follows which, at every scale. And when you prompt it, it continues the pattern, beautifully. But notice what it has never once done. It has never abstracted dog-ness from a dog, because it has never met a dog. It has abstracted the statistical shadow of the word "dog" from human talk about dogs. It has the third thing — the signs — in superabundance, and the first thing — the grasp of the nature — perhaps not at all. When it says I understand, it may be saying something for which there is, behind the words, no one who grasps. That is my position. The machine is a master of the surface and may be a stranger to the form, and the form is where understanding lives.

EDO SEGAL: Patricia.

CHURCHLAND: That was clearer than most things I read in journals, and I am going to agree with one piece of it and take the rest apart. Here is the piece I grant, and it is not small: today's systems are trained on text, the wake, as the friar says, and text is a thin and skewed slice of the world. Where the wake is thin, the competence thins with it, and the fluency keeps going. That is real, and I have spent years telling engineers to stop confusing a benchmark for a brain. So: granted.

Now the rest. The friar says the intellect's grasp of the universal cannot be the act of any organ, because organs receive particulars and universals are not particular. Watch the move, because everything turns on it, and it is, I am sorry to say, an argument from the inside of a thirteenth-century skull about what brains can do — written by a man who had never seen a neuron. Here is what we now know, that he could not. Your brain sits in the dark, in a box of bone. It never touches a dog either. It receives spike trains — patterns of electrical and chemical signal from the retina, the cochlea, the skin. From those patterns, eighty-six billion neurons, wired in parallel, build a model: edges into shapes into objects into the category "dog," distributed across the strengths of trillions of connections, not stored in any one place you could point to. When you "grasp the universal," what is happening is that a population of neurons has settled into a pattern of activity that the same population settles into for every dog and no cat. That is the abstraction. It is not immaterial. It is a vector in a very high-dimensional space, computed by wet tissue, and we can watch pieces of it happen on a screen.

So when the friar says the universality of the grasp proves the power is not material, my reply is the one I gave John Searle forty years ago. You are reasoning from "I can't see how matter could do this" to "matter cannot do this," and that inference has lost every single time it has been run. People once said a mere oscillating electromagnetic field could not possibly be light — you wave a magnet in a dark room and no glow appears, so light must be something more. They were wrong, defeated not by argument but by the physics of how fast the oscillation has to be. The friar's certainty that the grasp of a universal could not be the firing of a network is, I will wager, wrong in exactly that way. A failure of imagination, dressed as a proof.

But — and this is why I am a poor ally to the engineers as well — none of that means today's machine understands. The friar and I may converge on the verdict and split on the reason. He says the machine cannot understand because understanding is immaterial and the machine is matter. I say the machine probably does not yet understand because understanding is a particular kind of brain process — embodied, evolved, chemically regulated, built by a creature that has to keep a body alive in a world that pushes back — and the machine has captured one principle of that process, distributed learned representation, while leaving out almost everything else. He thinks the ceiling is metaphysical. I think the ceiling is biological, and biology can, in principle, be rebuilt. That is the whole evening, Edo. Two people who will mostly agree the machine isn't there yet, for reasons that could not be more opposed about what you are.

EDO SEGAL: Before I frame the rounds, one discipline I impose on every long conversation, because it pays off two hours later. Each of you, briefly — what do you envy in the other's position? Not respect. Envy. The thing their side gets to have that yours does not. Father first.

AQUINAS: I envy the laboratory. Patricia gets to go and look. When she wonders how memory works, she can open the literature and find that the question has moved an inch closer to ground in her lifetime. My questions do not move that way; I argue them in the same place Aristotle left them, and I will die with them roughly where I found them. There is a loneliness in reasoning about what no instrument can reach. She gets to be surprised by the world on a Tuesday. I get only the surprise of my own confusion clearing, which is rarer and quieter. I envy the Tuesday.

CHURCHLAND: And I envy the floor under his feet. The friar can say "this act is the signature of something that does not die," and it gives a man dying in Ohio a doorway. My honesty forbids me that. I have to tell that man the truth as I find it, which is that the lights go out, and that the meaning of his life was real and is now complete, not continued. There are nights when the naturalist's honesty is a cold thing to carry into a hospice. The friar gets to console with something he believes is true. I can only console with the dignity of the finite, and I have watched it not be enough for people I loved. I do not envy his metaphysics. I envy what it lets him say at a deathbed.

AQUINAS: That is the most honest thing anyone has said to me about my faith, and the kindest. Thank you.

EDO SEGAL: Two openings and two envies, and the architecture of the evening is already standing. It is not that one of them loves the machine and one fears it. It is that they locate the human difference in opposite places — one in an immaterial act that no matter could be, one in a material act so particular and so evolved that no current machine has it but some future one might. Hold both. We start the rounds with the smallest act in the world, the one the friar opened on. This cat, and cat-ness. After the break.