Two Definitions of a Living Thing

MORAVEC: Thank you. I want to start with a fact so ordinary that we walk past it every day, because the whole argument is hiding inside it. The atoms in your body are not the atoms you were born with. They are not even the atoms you had seven years ago. You eat, you breathe, you shed, you rebuild — the matter that composes you is a river running through a shape, and the shape stays while the water changes completely. The cells of your gut lining turn over in days. Even the long-lived neurons are swapping out their molecules constantly. So here is the first thing I want the audience to sit with: you are already not made of any particular stuff. You never were. The thing that has persisted from your childhood to this moment is not a lump of matter. It is an organization — a pattern of structure and process that the changing matter keeps re-instantiating.

I call this the pattern-identity view, and I set it against what I call body-identity — the common, unexamined conviction that you are a specific hunk of flesh. Body-identity is false, and you can prove it to yourself at the breakfast table. If you were the matter, you would have died a hundred times over by now, replaced by a stranger made of newer atoms. You didn't. You persisted through the replacement, which means the thing that is you was never the atoms. It was the pattern they were arranged into. And a pattern — this is the move that changes everything — is the kind of thing that can be read off one substrate and written onto another.

So picture the procedure. You're awake on a table. A surgeon — call it a very good machine — works on your brain one small region at a time. It measures, precisely, what a cluster of your neurons does: what comes in, what goes out, how they transform the one into the other. It builds an electronic device that does exactly the same thing, indistinguishably, and it swaps that device in for the biological tissue while you keep talking. You feel nothing change, because nothing relevant has changed — the function is identical. Then the next cluster. And the next. Region by region, your mind migrates from neurons to circuits, and at no point are you ever unconscious, at no point is there a gap, at no point does anyone die. At the end, the last of the meat is gone, and you — the same unbroken stream of you — are running on a machine. You walk out. The body stays on the table. And the question I want to leave with Aristotle is brutally simple: at which neuron did you die? Name it. Because if you can't name the neuron where the lights went out, then they never went out, and the thing that walked out the door is you, and I have just shown you that a life can be moved.

EDO SEGAL: Aristotle, before you answer — I want to make sure the reader has the strongest version of what he just said, because it's the engine of everything. The claim is: there is no fact about you over and above the organization of you, and so duplicating the organization duplicates you, full stop. The body is a scaffold, the pattern is the building, and you'd be a fool to mourn the scaffold. Is that the version you find most compelling, Hans?

MORAVEC: It is, with one sharpening. It's not that I think the scaffold is worthless. The scaffold is precious — it's the only place the pattern has ever run. I think it's replaceable, which is a different and much more hopeful thing. Your love for your children doesn't live in particular carbon atoms. It lives in a structure. Save the structure, and you've saved the love.

EDO SEGAL: Aristotle. He has named your tradition's oldest temptation — to say the mind is one thing and the body another — and then weaponized your own biology against you, because you of all people know the atoms turn over. The floor is yours, and take all the time you need.

ARISTOTLE: I want to begin by agreeing with him, because half of what he said is not only true, it is mine. He says you are not a lump of matter. Correct. I spent my life arguing exactly that against the materialists of my own day. He says what persists is an organization, a structure, a pattern that the changing matter keeps instantiating. Correct again — I have a word for it, older than his, and the word is form. So let no one think the dispute is between his pattern and my flesh. We both reject the flesh-as-such. The dispute is about what kind of thing the form is.

Here is where he and I divide, and it is the deepest division a person can draw. Moravec thinks the form is information — a description, a blueprint, the sort of thing that can be written down, copied, transmitted, and re-instantiated anywhere, like the plan of a house. I think the form of a living thing is not a description of the thing. It is the thing — its actuality, its living, the activity of this matter being alive in this way. In [On the Soul] I put it precisely: the soul is the first actuality of a natural body that has life potentially within it. Read that slowly, because every word fights him. Actuality — not a plan but a doing. This body — not body in general but this one, with life in it, not described about it. The soul is to the body as sight is to the eye, as cutting is to the axe. You cannot have the cutting without the axe; cutting is not a file you copy off one axe and load onto another. It is what this axe does when it is an axe at all. Separate the cutting from the axe and you do not have portable cutting. You have nothing.

MORAVEC: But sight is portable. We copy it. A camera sees. A blind man gets an implant and sees again on different hardware —

ARISTOTLE: You copy seeing-in-general, the function. You have never once copied this man's seeing — his life of looking, accumulated, his eyes that have wept and aged and learned this particular face. You build a new axe that also cuts. Splendid. You have not moved the old axe's cutting into it. You have built a second axe. And that, precisely, is what your surgery does. Let me answer your brutal question with the seriousness it deserves, because it is a good question and it has a precise answer.

EDO SEGAL: The neuron. He asked you to name the neuron where you die.

ARISTOTLE: And the answer is that he has hidden the death inside the word "identical." He says each electronic replacement does "exactly the same thing." But the same thing as what? It produces the same outputs. The wax takes the same impression. He has shown me a copy so good I cannot tell it from the original from the outside — and then declared that being indistinguishable from the outside is being the same on the inside. That is the entire trick, performed in a single adjective. I do not need to name the neuron where the man dies, any more than I need to name the brick at which a forged painting becomes the original. It never becomes the original. At every stage you have the living man plus a growing region of excellent forgery, and at the end you have a complete excellent forgery and a dead man, and the smoothness of the transition is not evidence that no one died. It is the anesthetic that lets you not notice.

MORAVEC: That's begging the question and you know it. You're assuming the electronic part is a forgery rather than a continuation. I gave you a reason it's a continuation — unbroken consciousness, no gap, no copy event. You answered "forgery" by fiat.

ARISTOTLE: No. I answered it from a principle you have not refuted: that the form of a living thing is inseparable from the matter whose form it is. Your "unbroken consciousness" is the very thing in dispute — you assume the stream continues into the circuit; I say you have no access to whether it does, only to whether it appears to from outside. You and I are not yet arguing. We are stating two definitions of a living thing, and the audience should hold them side by side, because everything tonight grows from this root. He says: a living thing is a pattern of information, and patterns are portable. I say: a living thing is a particular matter actively living, and the living cannot be peeled off the liver.

EDO SEGAL: I want to stop the room, because we are two openings in and I already need a discipline I impose on every long conversation — it pays off two hours later. Each of you, briefly: what do you envy in the other's position? Not respect. Envy. The thing his side gets to have that yours doesn't. Hans first.

MORAVEC: I envy that his view comes with grief built in, and grief is load-bearing for meaning. If the body can't be saved, then every moment is final, and finality is where humans have always located preciousness. My view has to earn preciousness some other way, and on the bad nights I'm not sure I can. He gets to say "this is the only chance you'll ever get to be alive" and have it land like a bell. I have to say "you can always make more of yourself," and somehow that's colder, even though it's more hopeful. I envy the bell.

ARISTOTLE: And I envy the hope. I taught that the human good is bounded by death — that a life has a shape because it ends, the way a melody is a melody because it stops. That is true, and it is also a consolation I built for people who had no other option. Moravec has, perhaps, another option. He stands in front of the dying and says maybe not, and I have stood in front of the dying and could only say bear it well. If he is right, I spent my life teaching people to make peace with a wall that has a door in it. I do not think he is right. But I would give a great deal to be the one holding the key, and I will not pretend the wanting isn't there.

EDO SEGAL: Two openings, two envies, and the architecture of the evening is already standing. Notice it isn't that one of them loves the machine and one fears it — Aristotle is not afraid of the machine at all, and Moravec is not in love with it; he's in love with what it might carry. The fork is deeper. One says you are the actual living of this actual body, and it ends. The other says you are a pattern this body is merely running, and it doesn't have to. Hold both. We start the rounds at the place the whole quarrel was born — twenty-three centuries ago, in a treatise about a soul, with an image of a seal and a piece of wax.