Gerald Sacks

Gerald Enoch Sacks (born October 4, 1933, in Brooklyn, New York; died October 4, 2019) was an American logician whose most important contributions were in recursion theory. He is credited with Sacks forcing, a forcing notion based on perfect sets, and the Sacks Density Theorem, which states that the partial order of recursively enumerable Turing degrees is dense. Sacks held a joint appointment as a professor at the Massachusetts Institute of Technology and at Harvard University starting in 1972. He became emeritus at M.I.T. in 2006 and at Harvard in 2012. Sacks earned his Ph.D. in 1961 from Cornell University under the guidance of J. Barkley Rosser, with his dissertation titled "On Suborderings of Degrees of Recursive Insolvability." He had several notable students, including Lenore Blum, Harvey Friedman, Sy Friedman, Leo Harrington, Richard Shore, Steve Simpson, and Theodore Slaman.