The Fixation of Belief and How to Make Our Ideas Clear

Two essays published in Popular Science Monthly in November 1877 and January 1878 as the opening papers of his series 'Illustrations of the Logic of Science'; together they founded pragmatism. 'The Fixation of Belief' treats inquiry as the struggle to move from the irritation of doubt to the settled state of belief, a habit that guides action. Peirce compares four ways of fixing belief: tenacity, clinging to what one already thinks; authority, imposed by institutions; the a priori method, accepting what seems agreeable to reason; and the method of science, which lets beliefs be determined by real things independent of us, and is the only one that allows a right and a wrong way of inquiring. 'How to Make Our Ideas Clear' criticises Descartes's test of clear and distinct ideas and proposes the pragmatic maxim: our idea of an object is our idea of its conceivable practical effects. He applies it to hardness, weight and reality, and links truth to the opinion all inquirers are fated to agree on.

Short and readable, these essays launched pragmatism and still offer one of the best tests for clearing up empty disputes: ask what practical difference a claim would make.