84 The very important difference between value in use and value in exchange was recognized oven by Aristotle. _Aristot._ Pol. I, 9. _Hutchinson_, System of Moral Philosophy (1755), II, 53 ff. The Physiocrates speak very frequently of _valeur usuelle_ and _vénale_, on which, according to _Dupont_, Physiocratie, CXVIII, the difference between _biens_ and _richesses_ is based. _La valeur d’un septicr de blé, considéré comme richesse ne consiste que dans son prix._ (_Quesnay_, éd. Daire, 300.) _Turgot_ distinguishes between “_valeur estimative_” and “_échangeable_ or _appréciative_;” the former designating the relation between the amount of energy, physical and mental, which one is willing to spend in order to obtain the goods, to the sum total of his energies, physical and mental; the latter the relation between the aggregate like energy of two persons which they are willing to spend in order to procure each of the goods to be exchanged, and the sum total of their energies in general. (Valeurs et Monnaies, p. 87, seq., éd. Daire.) _Ad. Smith_, in his Wealth of Nations, I, ch. 4, shows that he knew the difference between value in use and value in exchange; but he afterwards drops the consideration of the former, altogether. In this respect he has had only too faithful and one-sided followers among his countrymen, so that _Ricardo_, Principles, ch. 28, asks what value in exchange can have in common with the capacity of commodities to serve as food or clothing. (See, however, ch. XIX seq.) Many “free traders” would have no objection to interpose, if a people should abandon the cultivation of wheat, etc., to devote themselves exclusively to the manufacture of point lace, provided the latter had a greater value in exchange. The two degrees of the idea of value have been examined with much thoroughness by _Hufeland_ in his Neue Grundlegung der Staatswirthschaftskunst (1807), I, 118 ff.; _Lotz_, Revision der Grundbegriffe (1811 ff.), I, 31, ff.; _Storch_, Handbuch, I; _Rau_, Lehrbuch, I, 56, ff.; _Thomas_, Theorie des Verkehrs, I, p. 11; _Knies_, Tübing. Zeitschr. 1855; _Bastiat’s_ declaration (Harmonies, p. 171 ff.): that “_valeur_” (by which Bastiat means only value in exchange), = _le raport de deux services échangés_, contains a two-fold error: the ambiguity of the word _services_, which applies equally to a yielding or affording of utility, as to useful labor, and the error that the labor necessary to produce a commodity, and of which the purchaser is relieved, alone determines its value in exchange. Compare _infra_ §§ 47, 107, 110, 115 ff., and _Knies_, loc. cit., p. 644 ff. _ 85 Proudhon_, Système des Contradictions économiques, 1846, ch. 2.