 Reichenbach’s Direction of Time (1956) was centrally concerned with temporally asymmetric phenomena. Much of the work is devoted to the status of the Second Law of Thermodynamics, which says that in a closed system, entropy can increase but will never decrease. But Reichenbach also tried to define a macroscopic statistical asymmetry using the Common Cause Principle. Suppose that events A and B are correlated, i.e., that \(p(A \cap B) &gt; p(A)p(B)\). If there is an event C that satisfies conditions  (2)–(5)  above, Reichenbach called the trio ACB a conjunctive fork. If C occurs earlier than A and B, and there is no event satisfying (2)–(5) that occurs later than A and B, then ACB is said to form a conjunctive fork open to the future (see  Figure 6(a)). 