William Stanley JEVONS (1835–1882), British economist and lo - Lot 44

William Stanley JEVONS (1835–1882), British economist and logician. L.A.S., Manchester, May 12, 1874, to Professor Léon Walras; 7 pages, in-8 format (ink stamp of the H. Monge collection); in English. A very interesting letter on economics addressed to Léon Walras. Jevons thanks Walras for his letter and his paper [Principles of a Mathematical Theory of Exchange], which he had already noted in the *Journal des Économistes*. Their research is aligned, and he is delighted that his “theory of exchange”—which had been overlooked and criticized upon its publication in England—is now confirmed by Walras. Jevons had taken an interest in it as early as 1862 and presented a paper on the subject “at the meeting of the British Association in Cambridge”; a summary of which was published in 1866 in the Journal of the London Statistical Society, and a volume appeared from Macmillan in 1871 under the title *Theory of Political Economy*. We can thus see that their work coincides, despite different symbols and a few variations, certain aspects of which he elaborates upon: “The utility of a commodity is not proportional to its quantity; what you call the rarity of a commodity appears to be exactly what I first called the coefficient of utility, and later the degree of utility, which I also explained was really the differential coefficient of the utility considered as a function of the quantity of the commodity.” And he summarizes the theory of exchange in a single sentence: “An equivalence may then be established on either side between the utility gained and sacrificed at the ratio of exchange of the whole commodities, upon the last increments exchanged,” which can be expressed as an equation, which he sets forth and comments on…