JEVONS, WILLIAM STANLEY (1835-1882), English economist and logician, was born at Liverpool on Sept. I, 1835. His father, Thomas Jevons, a man of strong scientific tastes and a writer on legal and economic subjects, was an iron merchant. His mother was the daughter of William Roscoe. He was educated at University college school and University college, London. In 1853 he was appointed assayer to the new mint in Australia. He left England for Sydney in June 1854, and remained there for five years. In the autumn of 1859 he returned to University col lege, London, proceeding in due course to the B.A. and M.A. degrees of the University of London. Although he now gave his principal attention to the moral sciences, his interest in natural science continued throughout his life, and his intimate knowledge of the physical sciences contributed to the success of his chief logical work, The Principles of Science. In 1866 he was elected professor of logic and mental and moral philosophy and Cobden professor of political economy in Owens college. Next year he married Harriet Ann Taylor, whose father had been the founder and proprietor of the Manchester GUardian. Jevons, who suf fered from ill health, found the delivery of lectures covering so wide a range of subjects burdensome, and in 1876 he was glad to exchange the Owens professorship for the professorship of political economy in University college, London. He found his professorial duties irksome, and in 188o he resigned. On Aug. 13, 1882, he was drowned whilst bathing near Hastings.
Jevons arrived quite early in his career at the doctrines that constituted his most characteristic and original contributions to economics and logic. The theory of utility, which became the keynote of his general theory of political economy, was practi cally formulated in a letter written in 1860; and the germ of his logical principles of the substitution of similars may be found in the view which he propounded in another letter written in 1861, that "philosophy would be found to consist solely in pointing out the likeness of things." The theory of utility above referred to, namely, that the degree of utility of a commodity is some continuous mathematical function of the quantity of the com modity available, together with the implied doctrine that eco nomics is essentially a mathematical science, took more definite form in a paper on "A General Mathematical Theory of Political Economy," written for the British Association in 1862. This
paper does not appear to have attracted much attention either in 1862 or on its publication four years later in the Journal of the Statistical Society; and it was not till 1871, when the Theory of Political Economy appeared, that Jevons set forth his doctrines in a fully developed form. After the publication of this work Jevons became acquainted with the applications of mathematics to political economy made by earlier writers, notably A. A. Cour not and H. H. Gossen. The theory of utility was about 1870 being independently developed on somewhat similar lines by Carl Men ger in Austria and M. E. L. Walras in Switzerland. As regards the discovery of the connection between value in exchange and final (or marginal) utility, the priority belongs to Gossen, but this in no way detracts from the great importance of the service which Jevons rendered to English economics by his fresh discovery of the principle. In his reaction from the prevailing view he some times expressed himself without due qualification : the declaration, for instance, made at the commencement of the Theory of Politi cal Economy, that "value depends entirely upon utility," lent itself to misinterpretation.
It was not, however, as a theorist dealing with the fundamental data of economic science, but as a brilliant writer on practical economic questions, that Jevons first received general recogni tion. A Serious Fall in the Value of Gold (1863) and The Coal Question (1865) placed him in the front rank as a writer on ap plied economics and statistics; and he would be remembered as one of the leading economists of the 19th century even had his Theory of Political Economy never been written. Amongst his economic works may be mentioned Money and the Mechanism of Exchange (1875), a Primer on Political Economy (1878), The State in Relation to Labour (1882), and two posthumous works, Methods of Social Reform and Investigations in Currency and Finance. The last-named volume contains Jevons's speculations on the connection between commercial crises and sun-spots. He was engaged at the time of his death upon the preparation of a large treatise on economics; this fragment was published in 1905 under the title of The Principles of Economics: a Fragment of a Treatise on the Industrial Mechanism of Society, and other Papers.