Leo Harrington

Leo Anthony Harrington (born May 17, 1946) is a professor of mathematics at the University of California, Berkeley who works in recursion theory, model theory, and set theory.
Harrington and Jeff Paris proved the Paris–Harrington theorem.
Harrington showed that if the Axiom of Determinacy holds for all analytic sets then x# exists for all reals x.
Harrington and Saharon Shelah showed that the first-order theory of the partially ordered set of recursively enumerable Turing degrees is undecidable.