Mill's proof of the principle of utility

Abstract

John Stuart Mill’s proof of the Principle of Utility is deductively valid when interpreted through his technical vocabulary and instrumentalist theory of practical reasoning. The first stage of the argument, moving from the fact of desire to the desirability of happiness, relies on a foundationalist structure where “desirable” is synonymous with “desired” at the terminus of a chain of justification. This renders the inference a tautological repetition consistent with Mill’s radical empiricist rejection of deductive proof as a source of new information. The second stage, moving from individual to general happiness, is secured by the “decided preference criterion,” which identifies the good with the preferences of the experientially privileged. By projecting a future where social institutions produce a majority of natural utilitarians, the general happiness becomes desirable for every individual. However, this reconstruction reveals a fundamental incoherence in the underlying theory of practical reasoning. Instrumentalism cannot justify the “black box” of corrected preferences without resorting to non-instrumental inference, which it explicitly excludes. Ultimately, this moral theory fails because it rests on an unexamined, a priori account of practical reason that contradicts Mill’s broader empiricist commitments. – AI-generated abstract.