Evert Willem Beth

Evert Willem Beth (7 July 1908 – 12 April 1964) was a Dutch philosopher and logician, whose work principally concerned the foundations of mathematics.

Beth was born in Almelo, a small town in the eastern Netherlands. His father had studied mathematics and physics at the University of Amsterdam, where he had been awarded a Ph.D. Evert Beth studied the same subjects at Utrecht University, but then also studied philosophy and psychology. His 1935 Ph.D. was in philosophy.

In 1946, he became professor of logic and the foundations of mathematics in Amsterdam. Apart from two brief interruptions – a stint in 1951 as a research assistant to Alfred Tarski, and in 1957 as a visiting professor at Johns Hopkins University – he held the post in Amsterdam continuously until his death in 1964. His was the first academic post in his country in logic and the foundations of mathematics, and during this time he contributed actively to international cooperation in establishing logic as an academic discipline.

In 1953 he became member of the Royal Netherlands Academy of Arts and Sciences.

He died in Amsterdam.

The definition theorem states that a predicate (or function or constant) is implicitly definable if and only if it is explicitly definable. Further explanation is provided under Beth definability

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