De Morgan, Augustus (1806–1871)

Indian-born British mathematician. He initiated and developed a theory of relations in logic. He devised a symbolism that could express such notions as the contradictory, the converse, and the transitivity of a relation, as well as the union of two relations.

In his books Formal Logic (1847) and Syllabus of a Proposed System of Logic, De Morgan developed a logic of noun expressions. He also extended his syllogistic vocabulary using definitions, giving rise to new kinds of inferences, both direct (involving one premise) and indirect (involving two premises). He was thus able to work out purely structural rules for transforming a premise or pair of premises into a valid conclusion.

De Morgan was born in Madura (now Madurai), Tamil Nadu, India, and studied at Cambridge. He was the first professor of mathematics at University College, London 1828–58.