Hans Reichenbach

Hans Reichenbach was a German philosopher of science and a leading figure in logical empiricism, who founded the Berlin Circle in 1928 as a counterpart to Vienna's own circle of scientifically oriented philosophers. Reichenbach distinguished between the context of discovery, the psychological and historical process by which a scientist arrives at a hypothesis, and the context of justification, the logical structure by which that hypothesis is tested and confirmed, a distinction that shaped later philosophy of science's focus on justification over discovery. He made lasting contributions to the philosophical interpretation of Einstein's theory of relativity in his 1928 book The Philosophy of Space and Time, distinguishing axioms of coordination, which link abstract geometry to physical measurement, from purely mathematical axioms of connection. Reichenbach also developed an influential frequency interpretation of probability and, in his posthumously published book The Direction of Time, proposed an analysis of time's asymmetry rooted in the increase of entropy. Dismissed from his position in Berlin under Nazi racial laws in 1933, Reichenbach emigrated first to Istanbul and then in 1938 to the University of California, Los Angeles, where he helped build one of the leading philosophy of science departments in the United States and mentored students including Carl Hempel.