 The Theory of Probability uses class terms—A, B, C—and individual variables—x, y, z—as well as real variables—p, q, u, r, w. Distinct individual variables are (unnecessarily) sometimes and sometimes not associated with distinct class names, but Reichenbach’s formulae without iterated probability conditionals can be read as universally quantified with a single individual variable. The earlier 10 axiom schemes for probability implication (1925d) are replaced by 4 axiom schemes expressed in Reichenbach’s abbreviated form as (1949f, p. 53–65): 