Alonzo Church

Alonzo Church (June 14, 1903 – August 11, 1995) was an American mathematician and logician who was responsible for some of the foundations of theoretical computer science. Born in Washington, DC, he received a bachelor's degree from Princeton University in 1924, completing his Ph.D. there in 1927, under Oswald Veblen. After a post-doctoral fellowship at Göttingen, he taught at Princeton, 1929–1967, and at the University of California, Los Angeles, 1967–1990.

Mathematical work

Church is best known for the following accomplishments:

• His proof that Peano arithmetic and first-order logic are undecidable. The latter result is known as Church's theorem.
• His articulation of what has come to be known as Church's thesis.
• He was the founding editor of the Journal of Symbolic Logic, editing its reviews section until 1979.
• His creation of the lambda calculus.

The lambda calculus emerged in his famous 1936 paper showing the existence of an "undecidable problem". This result preceded Alan Turing's famous work on the halting problem which also demonstrated the existence of a problem unsolvable by mechanical means. He and Turing then showed that the lambda calculus and the Turing machine used in Turing's halting problem were equivalent in capabilities, and subsequently demonstrated a variety of alternative "mechanical processes for computation." This resulted in the Church-Turing thesis.

The lambda calculus influenced the design of the LISP programming language and functional programming languages in general. The Church encoding is named in his honor.

Students

Church's doctoral students were an extraordinarily accomplished lot, including C. Anthony Anderson, Peter Andrews, Martin Davis, Leon Henkin, John George Kemeny, Stephen Kleene, Gary Mar, Michael O. Rabin, Hartley Rogers, Jr, J. Barkley Rosser, Dana Scott, Raymond Smullyan, and Alan Turing. See [1].

Death

He died in 1995 and was buried in Princeton Cemetery.

See also

• Church-Turing-Deutsch principle
• Higher-order logic
• Universal set
• Church-Rosser theorem

Books

• Alonzo Church, Introduction to Mathematical Logic (ISBN 0-691-02906-7)

Sources and external links

• O'Connor, John J; Edmund F. Robertson "Alonzo Church". MacTutor History of Mathematics archive.  
• H B Enderton, In memoriam: Alonzo Church
• Alonzo Church at the Mathematics Genealogy Project
• "Fine Hall in its golden age: Remembrances of Princeton in the early fifties" by Gian-Carlo Rota. Contains a section on Church at Princeton.
• Interview of Church about his time at Princeton
• Archived papers
• A bibliography of Church's reviews for The Journal of Symbolic Logic, with a link to each

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