 He was productive throughout his career, publishing such important papers as “The Function of General Laws in History” (1942) and “Studies in the Logic of Confirmation”, “Geometry and Empirical Science”, and “The Nature of Mathematical Truth” (all in 1945), before leaving City College for Yale. While there, Hempel would publish “Problems and Changes in the Empiricist Criterion of Meaning” (1950) and “The Concept of Cognitive Significance: A Reconsideration” (1951), as well as his first book, a volume in the International Encyclopedia of Unified Science, Fundamentals of Concept Formation in Empirical Science (1952). Hempel moved to Princeton in 1955, where his research program flourished and his influence upon professional philosophers became immense.