Saunders Mac Lane (1909–2005) was professor of mathematics at the University of Chicago for thirty-five years and Max Mason Distinguished Service Professor for almost twenty of those years. A graduate of Yale University (Ph.B.), the University of Chicago (M.A.), and Göttingen University in Germany (Ph.D.), Mac Lane served as vice president of the National Academy of Sciences and also helped to edit several scholarly journals, including the Journal of Algebra. His books include Sheaves in Geometry and Logic: A First Introduction to Topos Theory. Mac Lane was awarded the National Medal of Science in 1989.