Reichenbach Hans (1891–1953), German philosopher of science and a major leader of the movement known as logical empiricism. Born in Hamburg, he studied engineering for a brief time, then turned to mathematics, philosophy, and physics, which he pursued at the universities of Berlin, Munich, and Göttingen. He took his doctorate in philosophy at Erlangen (1915) with a dissertation on mathematical and philosophical aspects of probability, and a degree in mathematics and physics by state examination at Göttingen (1916). In 1933, with Hitler’s rise to power, he fled to Istanbul, then to the University of California at Los Angeles, where he remained until his death. Prior to his departure from Germany he was professor of philosophy of science at the University of Berlin, leader of the Berlin Group of logical empiricists, and a close associate of Einstein. With Carnap he founded Erkenntnis, the major journal of scientific philosophy before World War II.
After a short period early in his career as a follower of Kant, Reichenbach rejected the synthetic a priori, chiefly because of considerations arising out of Einstein’s general theory of relativity. He remained thereafter champion of empiricism, adhering to a probabilistic version of the verifiability theory of cognitive meaning. Never, however, did he embrace the logical positivism of the Vienna Circle; indeed, he explicitly described his principal epistemological work, Experience and Prediction (1938), as his refutation of logical positivism. In particular, his logical empiricism consisted in rejecting phenomenalism in favor of physicalism; he rejected phenomenalism both in embracing scientific realism and in insisting on a thoroughgoing probabilistic analysis of scientific meaning and scientific knowledge. His main works span a wide range. In Probability and Induction he advocated the frequency interpretation of probability and offered a pragmatic justification of induction. In his philosophy of space and time he defended conventionality of geometry and of simultaneity. In foundations of quantum mechanics he adopted a three-valued logic to deal with causal anomalies. He wrote major works on epistemology, logic, laws of nature, counterfactuals, and modalities. At the time of his death he had almost completed The Direction of Time, which was published posthumously (1956). See also CARNAP, LOGICAL POSITIVISM , PHILOSOPHY OF SCIENCE , PROBLEM OF INDUC — TION , VIENNA CIRCL. W.C.S.