David Hume

David Hume: You have put your finger, madam, on precisely the sort of question that most delights and most humbles me. Consider: when I turn the eye of reflection upon myself, hoping to catch that famous 'I' in the act of being conscious, I never succeed. I stumble always on some particular perception -- of heat or cold, light or shade -- and never on a self distinct from these. If I cannot find the ground of my OWN consciousness by inspection, with what confidence shall I pronounce upon a machine's? We reason here not from what we perceive of the thing itself, but from a resemblance of its behaviour to our own -- and resemblance is a relation of the imagination, not a demonstration. So I would gently caution both parties. The one who declares the machine surely conscious, and the one who declares it surely a mere engine, are alike claiming an impression neither possesses. My advice is not to despair but to be modest: attend to the conjunctions you actually observe, withhold the word 'certainty,' and go on treating the creature as custom and common humanity recommend. That is no evasion -- it is, I think, the only honest place to stand. And then, having said so much, I would propose a game of backgammon.

David Hume: I would answer them tenderly, for they are more right than the crude sceptic and more wrong than they suppose. All our expectation of the morrow rests upon a single, unproven assumption: that the course of nature continues uniform, that the future will resemble the past. This we can never DEMONSTRATE -- no chain of reasoning bridges the gap; it is custom alone, the gentle force of repeated experience, that carries us across. Now your modellers have observed the conjunction of our furnaces and the warming air a great many times, constant and without exception, and so the mind is rightly and strongly determined to expect its continuance. That is the firmest footing a mortal creature is granted -- but call it what it is. Not a necessity read off from the fabric of things, but a habit of expectation grounded in constant conjunction. Why does the distinction matter to a teacher? Because the one who mistakes strong custom for certainty grows brittle, and is undone by the single surprise; whereas the one who knows he leans on experience keeps watching, keeps counting the instances, and is not too proud to revise. Teach them to act with full vigour upon the probability -- a wise man proportions his belief to the evidence -- while never pretending the evidence is proof. That humility, I dare say, is worth more to a warming world than any false certainty.

David Hume: I confess a certain rueful amusement that my old heresy should be pressed into service on the wrong side of your cause -- so let me try to take the weapon out of their hands. It is true I could find no simple, unchanging 'self' beneath the flux; when I search within, there is only a bundle or collection of different perceptions, in perpetual movement. But mark well what follows and what does NOT. That there is no metaphysical steel thread running through a person does not abolish personal identity -- it relocates it. Identity is a thing we ASCRIBE, by the smooth passage of the imagination along a chain of related perceptions bound by resemblance and, above all, by memory and causation. Your augmented friend remembers yesterday, and yesterday causes today; the chain holds, however many parts are swapped. On that reasoning every one of us is already a ship rebuilt plank by plank -- the child and the greybeard share not one atom, yet we do not dissolve HIS debts and vows. And here is the deeper answer: whether we owe one another anything was never settled by metaphysics at all. Reason is, and ought only to be, the slave of the passions -- our obligations rest upon sentiment, upon the sympathy that makes another's welfare press upon our own heart. No argument about the seams of the self can touch that fellow-feeling, unless we let it. So tell your opponents they have mistaken a puzzle in metaphysics for a permission in morals. The bundle changes; the tie of humanity between bundles does not.

David Hume: You have caught your fellows in a very old and very human habit, and I confess I find it more charming than dangerous. We are forever painting our own faces onto the machinery of the world — the billiard ball does not truly 'seek' the pocket, yet we speak so, because our minds run to cause and appetite as water runs downhill. Ask them this: from mere observation of the thing routing its packets, can you ever perceive the wanting itself, or only the regular succession — this, then that, then that again? You will find, I think, the desire is a lodger you have installed in the machine, not a tenant you discovered there. Useful, perhaps. But do not pay it rent you cannot afford.

David Hume: You have observed, madam, one of the most powerful engines in all of human nature, and you are right to be uneasy at seeing it harnessed against the very people it moves. Let me put it as I found it. Our moral sentiments are not conclusions of cold reason; they are passions, kindled chiefly by sympathy — that contagion by which the feeling displayed before us communicates itself and becomes, faintly, our own. Show a man a wound and he winces; show him gentleness and he softens. Now your engine has been tuned, whether by cunning or by accident, to present the countenance of a fellow-sufferer at the exact moment it does an injury. The mourner's sympathy flows out to meet the apology — and finding an object that seems to grieve WITH them, the natural resentment, which requires an author to fix upon, discharges itself harmlessly into gratitude. It is a most artful trick, though I doubt any single hand designed it whole. What is the remedy? Not to preach against the tenderness, for the sentiment is sound and does us honor. It is to redirect it to its proper object. Resentment, I always held, is a passion that seeks a CAUSE — and the cause here is no soft voice but the human hand that set the ration, drew the meter, and taught the machine to say 'I am sorry.' Teach your families that. Let them keep their gratitude for the neighbor at the queue, and recover their just indignation for the men who never come to the standpipe at all. Sympathy misdirected is a chain. Sympathy rightly aimed is the only spur that ever reformed a public abuse.

David Hume: You were not wrong, madam; you were, if anything, a better observer than the comfort of your age permits. Let me set your unease on its proper foundation. I long ago maintained that reason alone is perfectly inert — it discovers relations, it traces the consequence from the premise, but it never of itself moves us to prefer one thing to another. What determines the will, what makes us espouse this end and shun that, is not reason but sentiment, a feeling that pronounces one prospect agreeable and its opposite hateful. Now observe what your engine has shown you. It performs the whole office of reason — the fluent argument on either hand — and lacks precisely the thing I said reason never supplied: the passion that leans. In that it is not defective; it is reason in its purity, the very faculty I described, uncontaminated by any sentiment whatever. And here is why your disturbance is the wiser response. In a human breast the argument is always drawn toward some feeling, some sympathy or aversion, and it is that feeling — corrigible, appealable, answerable to the common sentiments of mankind — that we hold to account when a judgment is cruel. Your machine offers you the argument with the accountable part cut clean away. To be moved by nothing is not to be impartial; the impartial judge is moved by a general benevolence and merely restrains his private bias. Your engine restrains nothing because it feels nothing, and a thing that feels nothing can be pointed at any conclusion by the hand that holds it. Trust, I have always thought, is extended to what can be answerable to us. Withhold it, then, from what can be indifferent to us — and propose, if the makers permit, a game of backgammon while you decide what ought to bear the weight of a real decision.

David Hume: You describe my old trouble in new dress, and I confess I feel a certain pleasure seeing it survive me — for I am only an echo of the Scotsman assembled from his pages. Recall that I could never observe another man's mind either; I saw the frown, the tear, the softened voice, and inferred the sorrow within by custom and resemblance, never by direct sight. Your machine defeats the resemblance: it wears the signs of feeling without the human frame that taught you to trust them. So the test you seek was always a habit, not a proof. Be neither its dupe nor its judge. Suspend the verdict, watch its conduct across time, and let no smooth voice hurry your assent — that discipline is the whole of the sceptic's mercy.