 Hans Reichenbach’s The Direction of Time was published posthumously in 1956. In it, Reichenbach is concerned with the origins of temporally asymmetric phenomena, particularly the increase in entropy dictated by the second law of thermodynamics. In this work, he presents the first fully developed probabilistic theory of causation, although some of the ideas can be traced back to an earlier paper from 1925 (Reichenbach 1925).