John Phillip Preskill (born January 19, 1953) is an American theoretical physicist and the Richard P. Feynman Professor of Theoretical Physics at the California Institute of Technology (Caltech).Preskill was born in Highland Park, Illinois. After earning a B.A. in physics at Princeton University, summa cum laude, in 1975, he received his Ph.D. in the same subject from Harvard University in 1980.