A System of LogicJohn Stuart Mill

Mill's A System of Logic is the most ambitious empiricist account of reasoning and scientific method produced in the nineteenth century. Its aim is to show that all knowledge, including logic and mathematics, ultimately rests on experience and induction, not on a priori intuition.

The early books analyze propositions, names, and the syllogism. Mill argues that the syllogism does not actually prove anything new; its conclusion is already contained in its premises. The real engine of discovery is induction: the move from particular observations to general laws. Book III, the heart of the work, lays out Mill's four methods of experimental inquiry (agreement, difference, residues, concomitant variations) as the canons by which causal connections are established. These methods formalize what working scientists already do and remain a standard reference in the philosophy of science.

The later books extend the inductive framework to the "moral sciences," what we would now call the social sciences. Mill argues that human behavior is lawful, subject to causal explanation, and amenable to scientific treatment, though prediction in social matters will always be less precise than in physics. He rejects the intuitionist position that moral and political truths are self-evident, insisting that they too must be tested against experience. The work gave philosophical rigor to the empirical tradition running from Bacon through Hume and provided the methodological foundation on which Mill's own political and ethical writings rest.