Charles Sanders Peirce

Peirce was the son of the Harvard mathematician Benjamin Peirce, who drilled him from childhood in logic games and sensory discrimination; he had finished a logic textbook by twelve. He studied chemistry at Harvard, joined the United States Coast Survey in 1861 and did thirty years of scientific work, measuring gravity and the wavelength of light, the first to define the metre by a wavelength. He could write a question with his left hand and its answer with his right at the same time, suffered lifelong from trigeminal neuralgia and had a violent temper.

In 1879 he became lecturer in logic at Johns Hopkins, where Dewey was among his students, but in 1884 he was dismissed after the scandal of having lived with his mistress before divorcing his first wife, and never held an academic post again. In 1887 he used an inheritance to buy a house at Milford, Pennsylvania, and wrote there in poverty for twenty-seven years, living on book reviews and a fund of friends that James organised, without money for coal in winter, and died leaving eighty thousand pages of unpublished manuscript.

In the 1870s, in the 'Metaphysical Club' in Cambridge, he formulated the pragmatic maxim: to make a concept clear, consider what conceivable practical effects its object might have; the sum of those effects is the whole meaning of the concept. 'How to Make Our Ideas Clear' of 1878 is the founding document of pragmatism. James credited him publicly in 1898 but stretched the maxim into a theory of truth; to mark the difference Peirce renamed his own doctrine 'pragmaticism', a name he said was ugly enough to be safe from kidnappers.

His other work was almost unknown in his lifetime: he independently invented quantifier logic and the logic of relations, built a semiotics centred on triadic relations, dividing signs into icons, indices and symbols; proposed 'abduction' as a third mode of inference beside deduction and induction; held that truth is the opinion on which the community of inquirers would agree in the indefinite long run; and argued that the laws of the universe themselves evolve and that chance is real. Dewey, Royce, Quine, Putnam, Habermas and Eco all mined his manuscripts.