 Described as perhaps “the greatest empiricist of the 20th century” (Salmon, 1977a), the work of Hans Reichenbach (1891–1953) provides one of the main statements of empiricist philosophy in the 20th century. Provoked by the conflict between (neo-) Kantian a priorism and Einstein’s relativity of space and time, Reichenbach developed a scientifically inspired philosophy and an uncompromisingly empiricist epistemology. He was literate in the physical science of his time, and acquainted with many of its most eminent practitioners. Criticism and justification of scientific methodology formed the core of almost all his philosophical efforts, which he promoted in a crescendo of books, in the journal Erkenntnis, which he founded and edited with Rudolf Carnap, and within a group of philosophers, mathematicians and scientists he led in Berlin. His commitment to objectivity and realism in science together with his probabilistic justification of belief in scientific results carried philosophical and technical difficulties that shaped much of the subsequent debate in philosophy of science. Reichenbach’s contributions cover large swathes of formal philosophy, especially in philosophy of physics, logic, induction and the foundations of probability, and his later work encompassed linguistics, philosophical logic, and ethics. The fruits of some of his insights are only belatedly having their full impact. For example, several of the recent accounts of causality employ ideas that can be traced to Reichenbach’s The Direction of Time. 