 PCC*. The joint probability of any distinct, correlated events, x and y, which are not causally connected to each other, factorizes upon the union of their partial (separate) causes and their common cause. That is, let CC(x,y) denote the common causes of x and y, and PC(x) and PC(y) denote respectively their partial causes. Then, the joint probability of x and y factorizes upon the Union of their Causal Pasts (henceforth, FactorUCP), i.e., on the union of PC(x), PC(y) and CC(x,y):