Hempel Carl G(ustav) (1905–97), eminent philosopher of science associated with the Vienna Circle of logical empiricist philosophers in the early 1930s, before his emigration to the United States; thereafter he became one of the most influential philosophers of science of his time, largely through groundbreaking work on the logical analysis of the concepts of confirmation and scientific explanation. Hempel received his doctorate under Reichenbach at the University of Berlin in 1934 with a dissertation on the logical analysis of probability. He studied with Carnap at the University of Vienna in 1929–30, where he participated in the ‘protocol-sentence debate’ concerning the observational basis of scientific knowledge raging within the Vienna Circle between Moritz Schlick (1882–1936) and Otto Neurath (1882–1945).
Hempel was attracted to the ‘radical physicalism’ articulated by Neurath and Carnap, which denied the foundational role of immediate experience and asserted that all statements of the total language of science (including observation reports or protocol-sentences) can be revised as science progresses. This led to Hempel’s first major publication, ‘On the Logical Positivists’ Theory of Truth’ (1935). He moved to the United States to work with Carnap at the University of Chicago in 1937–38. He also taught at Queens College and Yale before his long career at Princeton (1955–1975). In the 1940s he collaborated with his friends Olaf Helmer and Paul Oppenheim on a celebrated series of papers, the most influential of which are ‘Studies in the Logic of Confirmation’ (1945) and ‘Studies in the Logic of Explanation’ (1948, coauthored with Oppenheim). The latter paper articulated the deductive-nomological model, which characterizes scientific explanations as deductively valid arguments proceeding from general laws and initial conditions to the fact to be explained, and served as the basis for all future work on the subject. Hempel’s papers on explanation and confirmation (and also related topics such as concept formation, criteria of meaningfulness, and scientific theories) were collected together in Aspects of Scientific Explanation (1965), one of the most important works in postwar philosophy of science. He also published a more popular, but extremely influential introduction to the field, Philosophy of Natural Science (1966). Hempel and Kuhn became colleagues at Princeton in the 1960s. Another fruitful collaboration ensued, as a result of which Hempel moved away from the Carnapian tradition of logical analysis toward a more naturalistic and pragmatic conception of science in his later work. As he himself explains, however, this later turn can also be seen as a return to a similarly naturalistic conception Neurath had earlier defended within the Vienna Circle. See also CARNAP, COVERING LAW MODEL, EXPLANATION , PHILOSOPHY OF SCIENCE , VIENNA CIRCL. M.F.