Post

Emil Leon Post

Born: 11 Feb 1897 in Augustów, Poland
Died: 21 April 1954 in New York, USA

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Emil Post lived most of his life in USA. In his Ph.D. thesis (1921) he proved the consistency of the propositional calculus described in Whitehead and Russell's Principia mathematica . It marks the beginning of proof theory. He introduced the concepts of completeness and consistency. He attained results similar to Gödel, Church and Turing in the 1920's but did not publish them.

In 1936 he proposed what is now known as a Post machine, a kind of automaton which predates the notion of a program which von Neumann studied in 1946. Post showed that the word problem for semigroups was recursive insoluble in 1947, a problem posed by Thue in 1914.

References:

  1. Dictionary of Scientific Biography
  2. Obituary of E L Post, The Campus (City College) (1954). 
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JOC/EFR February 1996