ABSTRACT
Though the great idea is now known as marginal utility, Jevons himself did not use that term (he called it final utility). Value, Jevons insisted, must be given a precise meaning. The value of a commodity is its utility to us, and the utility of an article varies "according as we already possess more or less of the same article."2 The final degree of utility, which Jevons described as "that function upon which the theory of Economics will be found to turn," is based on the fact that each increment of a commodity possesses less utility than the previous one because this final portion is less urgently desired or needed: a pound of bread per day may be essential; a second, highly desirable though not indispensable; but a third, superfluous.
