(1834-1923) English logician whose diagram, known as the Venn diagram, is much used in the teaching of elementary mathematics.
Venn was born in Hull, Yorkshire, and studied at Cambridge. He became a priest, but abjured his clerical orders 1883. From 1862 he was a Cambridge college lecturer in moral sciences.
The use of geometrical representations to illustrate syllogistic logic was not new. Venn adopted the method of illustrating propositions by means of exclusive and inclusive circles, and added the new device of shading the segments of the circles to represent the possibilities that were excluded by the propositions at issue. Later, he extended his method by proposing a series of circles dividing the plane into compartments, so that each successive circle should intersect all the compartments already existing. This idea, taken up and refined by Charles Dodgson (the writer Lewis Carroll), led to the use of the closed compartment enclosing the whole diagram to define what is now known as the universal set.
Venn published three standard texts: The Logic of Chance 1866, Symbolic Logic 1881, and The Principles of Empirical Logic 1889.