Augustus De Morgan

Born in Madurai, India, in 1806, and appointed in 1828, aged twenty-one, as the first professor of mathematics at the newly founded University College London. He resigned the post twice on principle over how the college handled religious considerations in appointments, which says something about how literally he took a principle.

De Morgan's laws state that the negation of a conjunction is the disjunction of the negations: NOT (A AND B) equals (NOT A) OR (NOT B), and dually. In code that is the rewrite from !(a && b) to !a || !b — the one every developer performs by hand when a condition has become unreadable, and every optimising compiler performs without asking. He also introduced the term mathematical induction in 1838 and gave it its modern form, tutored Ada Lovelace in mathematics by correspondence from 1840, and defended George Boole's work during the years when almost nobody else would.