Mill's ‘proof’ of Utility and the composition of causes

Abstract

John Stuart Mill proposed that all policy precepts, be they in the areas of morality or prudence or aesthetics, are all subordinate to the precepts of the Art of Life. The value which he assumes in defining the Art of Life is the Principle of Utility. This principle, being normative rather than fact, can admit of no proof based solely on deductive inference. Yet Mill proposed considerations that he believed capable of rationally persuading one to accept his principle as the basic principle for the Art of Life. This paper aims to evaluate this argument. In particular, it tries to show that a crucial step, often thought to be a logical ‘howler’, is not to be so simply dismissed. It is shown that if one accepts certain theses from Mill's philosophy of science and of social science, concerning the composition of causes, then the crucial step is fully justified. It is also suggested that these theses of Mill's philosophy of science are mistaken. So Mill's ‘proof’ of utility is, after all, unsound, but the reconstruction proposed shows it to be much more plausible and much more philosophically interesting than is often thought.