We might naturally expect a superior treatment of exchange following upon this new theory of value. If value is simply the satisfaction of want, exchange creates two values when it satisfies two needs at the same time. The characteristic of exchange is that each of the two parties yields what it has in superabundance in return for what it needs. But what is given up is superabundant, is useless, and consequently valueless; what is demanded has greater utility, and consequently greater value. Two men come to market each with a useless thing, and each returns with a useful one.[119] Consequently the Physiocratic saying that exchange means no gain to anyone, or at least that the gain of one only compensates for the loss of the others, is seen to be radically false. The Physiocrats—notably Trosne—attempted a reply, but, for reasons already given, they never succeeded in realising the subjective character of value. This same theory should have carried Condillac a stage further, and helped in the rectification of the Physiocratic error concerning production. If value is simply utility and utility itself is just the correspondence between things and our demand for them, what is the agency that produces this harmony between things and desires? It is very seldom that nature succeeds in establishing it. “Nature is frequently fertile in things we have no desire for and lavish of what is useless”—a profound remark that ought to have cooled the Physiocrats’ love of the _Alma Parens_. “Matter is transformed and made useful by dint of human labour. Production means giving new form to matter.”[120] If this be true, then there is no difference between agricultural and industrial production, for they both transform what already exists.[121] Moreover, the theory proves very clearly that if artisans and proprietors are dependent upon the agriculturists—as, indeed, they are—the latter in their turn are nothing but artisans. “If someone asks whether agriculture ought to be preferred to manufacture or manufacture to agriculture, we must reply that we have no preferences, and that the best use should be made of both.”[122] Lastly, his definition of wages, short as it is, is of immense significance. “Wages represent the share of the product which is due to the workers as co-partners.”[123] Wages only “represent” the share that is due to the workers. In other words, the wage-earner, either through want of will or of power, cannot exercise his rightful claim to his own work, and simply surrenders the claim in return for a money price. This constitutes his salary, which is regulated, like every other price, by competition between buyers and sellers. Condillac makes no reference to an iron law of wages, but regards them as determined by the forces of demand and supply. He does, however, hint at the implicit alliance which exists between capital and labour.[124]