First collected edition, comprising some of Jevons’s major earlier works, and including the first appearance in book form of his essay entitled ‘John Stuart Mill’s philosophy tested’. Edited posthumously by the philosopher Robert Adamson and Harriet Jevons, the author’s wife.

Pure logic, first published in 1864, was Jevons’s first work on logic, and one of two pamphlets in which he developed the calculus presented by Boole in An investigation of the laws of thought (1854). Jevon’s other pamphlet – The substitution of similars (1869) – also appears here. Jevons’s principal advance was to reduce the operations of the Boolean calculus to a mechanical procedure. He here stood at the start of a road that led to the modern application of logic in computer-programming; he himself designed a ‘logical abacus’ (illustrated here) and ‘logical piano’, ancestors of the computer which performed the operations of the revised Boolean calculus, and which constitute precursors to the truth-table.