Actualism is a fundamental assumption of secular natural history. It replaced the Christian view of causality through providence, and it asserted an absolute physicochemical and geological continuity. Though often confused with uniformity and uniformitarianism due to secular obfuscation, actualism, at root, is a method of geology that limits historical processes and events to observed present-day causes. Actualism fails as an absolute explanation of historical causality: it cannot be precisely defined, it surreptitiously assumes unjustified metaphysical positions, and its secular formulations fail logical and empirical truth tests. Only when justified as a contingent manifestation of providence does it avoid these problems. However, that formulation is of little help in deciphering the rock record, because it was largely shaped by nonactualistic discontinuities.