What the Engine Cannot Do

There is a question I have never once succeeded in laying aside — it has cost me more in the small hours than any sum I ever set the operations to compute — and it is this: where, precisely, does the engine leave off, and where do I begin? I am asking it still, in this dim room, with the December of the year coming on and my reason guttering where it once burned steady; and I am no nearer the floor of the thing than I was that summer of 1843, bent over the proofs by lamplight, when I felt — for once in a life — that I had laid my hand flat against the very boundary of the possible, and could feel it pushing back against my palm.

Let me set down the wonder first; for I will not have it said that I came to my own creation with a cold heart.

I had written, in the Note I marked with the letter A, that the engine did not deal in Number alone. This was the thought that had taken me by the throat and would not let me sleep — that the cards, and the Store, and the Mill, care nothing whatever for what the symbols may mean, but only for the relations between them, the order in which one quantity is made to bow to another. Mr. Babbage had given the world a machine for arithmetic, and called that the half of his meaning; I saw — or believed that I saw — the whole. For if the engine could be brought to act upon the abstract relations of things, and not upon the things themselves, then it might act upon anything whose relations could be set down in the strict grammar of operation. I likened it then to the loom at Spitalfields, which weaves its brocaded flowers and curling leaves not because the weaver has painted them afresh, but because the punched cards command the threads; and I wrote that the Analytical Engine weaves algebraical patterns just as the Jacquard-loom weaves flowers and leaves.

And then I let myself go one step further into the dark — and I have never once repented it. Suppose, I wrote; suppose the science of harmony, the relations between pitched sounds, the intervals and consonances a master sets down when he composes, could be expressed in those same numerical relations, made tractable to the operations of the cards. Then the engine might compose elaborate and scientific pieces of music of any degree of complexity or extent. I remember the precise sensation of framing that sentence — not unlike the vertigo of the high gallery at Ashley Combe, where William had cut his terraces into the hillside, and one looks down through the trees to the sea and feels the ground at once firm and falling away. A machine of brass and steel, never yet built, fed with the right relations, might sing. Might lay down a fugue — not by accident, not as the wind frets a tune from a casement, but by reasoned construction, exactly and forever repeatable. I was not so many years out of my mother's schoolroom, where music had been pressed upon me as one of the rational accomplishments, a corrective to my father's fire; and I had taken that drilled and dutiful art and handed it to the engine as a thing it might one day do. I confess I was proud. I am proud of it yet.

But here is the discipline of the matter — and it is the harder half; and I set it down as the true summit of all my labour, higher than the music, higher than the patterns, higher even than the long ladder of operations I built in the last Note for the Numbers of Bernoulli.

For no sooner had I let the imagination off its leash than I called it sharply back. I wrote, in the Note I marked with the letter G, the sentence I believe will outlast every other I have committed to paper: The Analytical Engine has no pretensions whatever to originate any thing. It can do whatever we know how to order it to perform. I underscored the originate in my own mind, though not, I think, upon the page. It is the whole of my creed in a single clause. The engine composes nothing; it executes. It can follow the relations of harmony into a symphony of whatever extent you please — but only if some living soul has first conceived those relations, grasped them, ordered them, and laid them upon the cards. It anticipates no truth. It discovers no law it was not handed. It throws no new thing into the world. It is the most faithful servant ever contrived — and a servant only; it will run further, and faster, and with a patience no clerk could match, down whatever road we have surveyed for it, and not one inch down a road we have not.

I have heard it said — by warmer admirers than I deserve — that such a machine might one day think; might pass beyond its instructions into something resembling a mind. I do not believe it; I did not believe it even in the heat of my own enthusiasm; and I held the wonder and the warning in the one hand, on purpose, that neither should run away with the truth. The engine has no self to be surprised by. Whatever appears to issue from it was folded into it beforehand by the hand that set the cards; the cleverness is ours, lent out, and returned to us magnified — but not transmuted. The originating, the conceiving — the act by which a relation that was nowhere is of a sudden here, in a human skull, demanding to be born — that remains entirely upon our side of the boundary. That is the imagination, which my mother spent the whole of her vigilance labouring to school out of me, and which the engine, for all its brass, has not got, and shall never get. The faculty that so frightened her is the very faculty no mechanism can counterfeit. I find a tart justice in that, lying here.

Mr. Babbage — who is the warmer of us two by temperament, for all his quarrels with the world — was inclined, now and again, to let the engine swell into something grander than it was. He had carried the half of the Bernoulli computation himself; and I caught him in an error among his figures, and made him set it right — a small thing, but I mention it, for it taught me the texture of the engine's honesty. It does not forgive. Order it wrongly, and it will carry your mistake out to the last decimal place with perfect obedience and no blush whatever. There is no genius in it to save you from yourself. That is precisely why I could not let the music passage stand without the chain upon it. To promise the world a machine that originates is to promise a falsehood; and I would sign my Notes with my initials only, A.A.L., and quarrel with him over his angry unsigned preface, and very nearly break the whole collaboration upon a point of honour — but I would not, for any enthusiasm whatever, put my name to a thing that was not true.

And yet. And yet.

Here is where the dying woman parts company a little from the woman of nine years since; and I will be honest about the seam between them, for honesty is very nearly all I have left to spend. I called the engine's domain a servant's domain — bounded, modest, executing only — and some nights I wonder whether I did not draw that boundary too near in. For consider what lies within it, even so. Whatever we know how to order it to perform. The whole of analysis is folded into that one phrase. Every relation the mind of man has ever seized, or shall yet seize — in Number, in symbol, in the unfolding of one quantity from another — all of it is orderable; and therefore all of it is, in principle, within the engine's reach. The country behind the cards does not shrink because the engine cannot originate; it widens — for the engine can carry us so much further into it than our own short patience and shorter lives will allow. The limit is not the machine's poverty. The limit is the poverty of our ordering — how much we have yet learned to conceive, and to command. Push that frontier outward, and the servant follows you, tireless, into country no human reckoner could ever have walked to on foot.

So which is it — small, or limitless? I have decided that it is both; and that the doubled answer is no contradiction at all, but the truest thing I know. The engine is small in its nature and unbounded in its reach; it originates nothing, and may yet help us to originate everything; it is a mirror, and not a lamp — and a mirror set at the right angle may show us round corners we could never have turned alone. I shall not live to see it raised in iron and brass. I have made my peace — or very nearly — with knowing that the thing I understood better than any soul now living will stand only in a heap of drawings, and in my Notes, when I am gone into the Byron vault at Hucknall, beside the father I never met. I let the old boast stand — that what I conceived was made for more than my own short years. But I will add to it the discipline I gave the engine, for the two belong indissolubly together: I conceived; I did not finish. I ordered the cards for a Mill I shall never hear turning. Whether the world ever learns to order it further — that is the one operation I cannot compute from this bed, and must, with whatever faith is left in me, hand forward into the dark.