## de Morgan, Augustus (1806–1871)His most important published work, Formal Logic, included the concept
of the quantification of the predicate, an idea that solved problems
that were impossible under the classic Aristotelian logic. de Morgan coined
the phrase "universe of discourse,"
was the first person to define and name mathematical induction,
and developed a set of rules to determine the convergence
of a mathematical series. In addition, he devised a decimal coinage system,
an almanac of all full moons from 2000 BC to AD
2000, and a theory on the probability of life events that is still used
by insurance companies. de Morgan was also deeply interested in the history
of mathematics. In Arithmetical Books (1847) he describes the work
of over fifteen hundred mathematicians and discusses subjects such as the
history of the length of a foot, while in A Budget of Paradoxes he
gives a marvelous compendium of eccentric mathematics including the poem:
Great fleas have little fleas upon their backs to bite 'em,the first lines of which paraphrase a similar rhyme by Jonathan Swift. On one occasion, when asked his age, De Morgan replied: "I was x
years old in the year x." How old must he have been at the time?
(Answer: 43 – the only number that, when squared, gives a number between
the years of De Morgan's birth and death.) ## Related category• MATHEMATICIANS | ||||||

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