Value, the marginalists taught, is not a property of things but a relation between things and wants. A loaf of bread is worth nothing to the man who cannot eat another bite, and everything to the starving; the diamond is dear not because it costs much to find but because it is wanted and scarce. What a thing is worth, on this view, is fixed not by the labor it took to make nor the cost of its making but by the want it satisfies — by its utility, the service it renders to desire. This was the great inversion of the nineteenth century: value moved from the object to the subject, from the sweat in a thing to the wanting of it. And at the center of the new science stood utility, the measure of want, on which every price was now said to rest.
To grasp the inversion one must first see what it inverted. For the great classical economists, value came from the side of production. Adam Smith held that the real measure of a thing's worth was the labor it could command or the toil it had cost; David Ricardo refined this into the proposition that the relative values of goods are governed, in the main, by the relative quantities of labor required to produce them; and Karl Marx carried the labor theory to its most rigorous and most radical conclusion, making value the socially necessary labor congealed in a thing, and profit the portion of that labor the worker is not paid for. However they differed, the classicals agreed on the essential point: worth was rooted in the making, an objective residue of the effort and the resources a thing embodied. Value was something a thing carried within it, deposited there by the labor of its production — a property of the object, to be discovered by tracing it back to its cost.
Against this rooted and reassuring picture stood a puzzle the classicals could acknowledge but not dissolve. Smith himself had posed it: nothing is more useful than water, yet it will buy almost nothing; a diamond has scarcely any use, yet commands a great price. If value flowed from utility, water should be precious beyond reckoning; if from labor, the puzzle only sharpened, for much that costs great labor is cheap and much that costs little is dear. The classical answer was to cleave value in two — a value in use, which water has in abundance, and a value in exchange, which it lacks — and then to let exchange-value be governed by cost of production, quietly setting use-value aside as irrelevant to price. The distinction was old, older than Aristotle's separation of the proper use of a sandal from its use in barter; but as a solution it was an evasion, for it named the difficulty without explaining it. Why usefulness and price should diverge so wildly remained dark, and the darkness lay at the very center of the theory of value.
The overturning came in the eighteen-seventies, and it came three times at once. Working in ignorance of one another, William Stanley Jevons in Manchester, Carl Menger in Vienna, and Léon Walras in Lausanne arrived within a few years at the same revolutionary thought: that value originates not in the cost of a thing but in the want it satisfies — that a good is valuable because, and exactly insofar as, someone desires it. The thought was not wholly new. The Abbé de Condillac had argued a century earlier that things take their value from our need and our esteem, not from the labor in them; Ferdinando Galiani, earlier still, had made value a compound of utility and scarcity. But the marginalists made the insight systematic and raised a science upon it. Value, in their hands, ceased to be a property residing in the object and became a relation between an object and a desiring subject — and it was the subject's want, not the object's cost, that was the wellspring. The thing did not contain its value; the wanting conferred it.
The new doctrine triumphed because it explained what the old could not. It accounted at once for what the labor theory had to treat as anomaly: that the same loaf is worth nothing to the sated man and everything to the starving, though the labor in it is identical; that value rises and falls with circumstance, season, and mood while the toil embodied stays fixed; that a thing made with enormous effort but wanted by no one is worthless, while a thing got for nothing but keenly desired is dear. By placing value in want, the marginalists made demand a source of price alongside supply, where the classicals had let cost reign nearly alone. The psychological ground had been prepared by Jeremy Bentham, who made pleasure and pain the springs of all human action, so that to want a thing was to anticipate the pleasure it would bring; utility was simply that capacity to please or to serve, scaled to the wanting. And the ancient paradox began to dissolve — its full resolution belonging to the value of the last unit, worked out in the volume on the margin, but its direction now plain: water is cheap not because it is useless but because it is abundant, so that one more draught is wanted little. Within a generation, value-from-want was no longer heresy but the foundation of the field.
There is a democratic music to this doctrine, and it is worth hearing before one hears the discord beneath it. To locate value in want is to make the ordinary person's desire the source of worth, to crown the consumer sovereign, to ask of no one that he justify what he wants: his wanting is itself the ground of value, as good as any other's. Value becomes a fact about what people actually desire — a natural fact about the human heart, which price merely reads off and reports. A price is a verdict on a hidden contest, mistaken for a fact of nature; and here is the first place the mistaking enters, for the wants a market counts are not all wants but only those armed with the means to pay. Desire alone moves no market; desire backed by money does. The subjective theory, by defining value as want, lets the moneyed whim and the penniless need both pass under the single name of demand, and so presents as a neutral reading of what people want what is in truth a reading of what people want weighted by what they have. The consumer is sovereign, but the votes are counted in dollars.
Two defenses of the doctrine must be set down at their full strength. The first is that the subjective theory is simply correct as an account of value in exchange, and the labor theory simply wrong: things do trade at rates governed by the utility and scarcity of the last unit, and no rival theory survives contact with a found diamond, an old master, or a glass of water in a desert, none of which can be priced by the labor in them. To observe that markets weight wants by money is not to refute this account but to restate it, for a theory of price must reflect what people will actually give, and what they will give depends on what they have. The second defense is that placing value in want was a liberation, not an imposition: it freed economics from the metaphysics of intrinsic worth — from the notion that things possess a value independent of any valuer — and grounded value instead in real human preference rather than in custom, authority, or decree. Far from demeaning the ordinary person, it honors his desires as the very source of worth, asking no priest or aristocrat to certify what is good. On this view the subjective theory is the most respectful, and the most truthful, theory of value there has ever been.
Both defenses are sound, and neither reaches the difficulty. Grant that the subjective theory describes exchange truly and the labor theory fails: that very truth is what exposes the theory's limit as a measure of desire, for to describe how prices form is to show that the wants they register are filtered through wealth, and a filtered want is not the same as a want. The theory's correctness about the market is precisely its insufficiency about the heart. And grant the liberation: still the relocation of value from labor to want was never the innocent discovery it appeared. The labor theory had carried a claim — that the laborer, making the value, held a title to it — and the subjective theory quietly dissolved that claim, for if value springs from want and not from work, the worker creates no value to which he holds special right, and his wage, like every price, merely records a marginal contribution. The turn from labor to want thus cleared the ground for the marginal-productivity theory of distribution, in which each factor is paid its marginal product and the question of desert is declared already answered. A doctrine that decides, in passing, what the worker may claim of the worth he handles is doing work in a quarrel, however true its account of how a thing comes to have a price. It can be right about exchange and partisan about justice in the same breath.
The subjective theory of value is the foundation of the modern science, and the foundation is sound: value is a relation between things and wants, and the centuries spent seeking worth inside the thing were centuries spent looking in the wrong place. A price is a verdict on a hidden contest, mistaken for a fact of nature; and to have shown that value is want is to have located the contest, not to have dissolved it. For the wants a price records are weighted by the means to satisfy them, so that what is offered as a reading of desire is a reading of desire backed by money; and the doctrine that worth springs from wanting arrived in the world as a move in the long contest over how the product of labor should be divided. The want is real, and the theory that names it is true. But a price built upon that want measures desire only as far as wealth permits desire to speak, and calls the result the value of things. To read a price as a report on what human beings want, one must ask not what is wanted merely, but what is wanted by those who can pay — and, beneath that, whether the want it claims to register can be seen at all.
Value is not in the thing but in the wanting of it. A market counts the wants — but it counts them in dollars.
The want, then, is where value lives, and the marginalists were right to put it there. But a foundation one cannot inspect is an uneasy thing to build upon, and the want at the root of all value is, of all quantities, the least observable: felt with perfect certainty by the one who has it, and invisible to everyone else. The theory of value rests, that is, on a quantity that can be suffered but not seen, inferred but never measured directly — a circumstance the next plate examines, and finds more troubling than the triumph of the subjective theory has let most of its heirs admit. Value is a relation to human desire; whether that desire can be known is the question on which everything built upon it depends. The argument remains open.