Who was Alonzo Church?

Alonzo Church was an American mathematician who made most of his contributions to mathematics and logic while teaching at Princeton University.

His most famous accomplishment was the development of the λ-Calculus and the use of it to resolve the Entscheidungsproblem. His resolution of this problem became widely known as Church's Theorem. The Entscheidungsproblem was also resolved about the same time by Alan Turing in his paper where he introduced what became known as the Turing Machine. However, it is Alonzo Church who gets the credit for solving the Entscheidungsproblem because he published his paper first.

After the publication of both of these papers in 1936, Alan Turing came to Princeton to continue his studies in mathematics and received his Ph.D. in 1938 with Alonzo Church as his Ph.D. Advisor.

When Alonzo Church died in 1995, the New York Times carried a nice obituary about him.