Since textbook quantum mechanics already contains certain rules for calculating probabilities, the first innovation of the histories approach, stochastic dynamics, is not very startling and by itself causes few conceptual difficulties. It is the second innovation, in the domain of logic and ontology, that represents the most radical departure from classical thinking. However, the new quantum logic reduces to the old familiar classical propositional logic in the same domain where classical mechanics is a good approximation to quantum mechanics. That is to say, the old logic is perfectly good for all practical purposes in the same domain where classical mechanics is perfectly good for all practical purposes, and a consistent, fully quantum analysis explains why this is so.