Emil Leon Post reached a conclusion regarding the completeness of propositional calculus in 1921, effectively mapping the logic foundations of Principia Mathematica. His career evolved through significant mathematical research in the United States, spanning from his early doctoral studies at Columbia University to his long-standing teaching position at the City College of New York.
Academic Foundation
Born in Augustów in 1897, Post relocated to New York City as a child. He attended Townsend Harris High School and completed his B.S. at City College of New York before earning his Ph.D. at Columbia University in 1920 under the supervision of Cassius Jackson Keyser. His early professional path included a post-doctorate year at Princeton University, followed by stints at Cornell University and secondary school teaching before he secured a faculty appointment at City College of New York in 1932.
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Post independently developed truth tables and expanded the theory of elementary propositions. By 1936, he formulated a model of computation equivalent to the Turing machine, now referenced as the Post–Turing machine. His work on canonical systems, published in 1943, established methods for string rewriting that remain fundamental to modern programming language design. In 1946, he introduced the Post correspondence problem to demonstrate undecidability in formal languages.
Polyadic Groups and Post's Problem
Beyond his contributions to computability, Post conducted extensive research into polyadic, or n-ary, groups. His 1940 paper provided a foundational theorem proving that such structures could be expressed via standard group operations. Later, in an address to the American Mathematical Society in 1944, he proposed a question concerning the existence of an uncomputable recursively enumerable set with a Turing degree lower than the halting problem, a challenge now known as Post's problem.
Management of Health
Beginning during his time at Princeton, Post struggled with manic attacks. Following medical advice, he limited his daily research duration to no more than three hours. He was married to Gertrude Singer in 1929, with whom he had a daughter, Phyllis Post Goodman. Post died of a heart attack in New York City in 1954 after receiving electroshock treatment for depression and was buried at Mount Hebron Cemetery.
Fast facts
- Born: 1897, Augustów
- Died: 1954, New York City
- Education: City College of New York, Columbia University
- Spouse: Gertrude Singer
- Daughter: Phyllis Post Goodman
- Key Contribution: Post correspondence problem
- Final Resting Place: Mount Hebron Cemetery
Questions readers ask
What was the significance of the 1921 thesis?
It proved that the propositional calculus of Principia Mathematica was complete, meaning all tautologies were theorems.
Did Post discover Gödel's incompleteness theorem first?
Post came close to the discovery while at Princeton in 1921 but did not publish his ideas at that time.
Achievements
- Notable work: Post correspondence problem
- Notable work: Post's inversion formula
- Notable work: Post's lattice
- Notable work: Post's theorem
- Held posts at City College of New York, Princeton University and Columbia University
- Fields: mathematics
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