Church?Turing thesis

In computability theory the Church?Turing thesis, Church's thesis, Church's conjecture or Turing's thesis, named after Alonzo Church and Alan Turing, is a hypothesis about the nature of mechanical calculation devices, such as electronic computers.

History

The thesis is named after mathematicians Alonzo Church and Alan Turing. In his 1936 paper "On Computable Numbers, with an Application to the Entscheidungsproblem" Alan Turing tried to capture the notion of algorithm (then called "effective computability"), with the introduction of Turing machines. In that paper he showed that the 'Entscheidungsproblem' could not be solved. A few months earlier Alonzo Church had proven a similar result in "A Note on the Entscheidungsproblem" but he used the notions of recursive functions and lambda-definable functions to formally describe effective computability. Lambda-definable functions were introduced by Alonzo Church and Stephen Kleene (Church 1932, 1936a, 1941, Kleene 1935) and recursive functions by Kurt Gödel and Jacques Herbrand (Gödel 1934, Herbrand 1932). These two formalisms describe the same set of functions, as was shown in the case of functions of positive integers by Church and Kleene (Church 1936a, Kleene 1936). When hearing of Church's proposal, Turing was quickly able to show that his Turing machines in fact describe the same set of functions (Turing 1936, 263ff).

Related Topics:
Alonzo Church - Alan Turing - 1936 - Entscheidungsproblem - Recursive function - Lambda-definable function - Stephen Kleene - Kurt Gödel - Jacques Herbrand

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