Abstract

Quantum mechanics gives us reason to think both that the world is indeterministic, and that there are irreducibly statistical laws governing objectively chancy processes. Lewis notes that this raises a two-horned dilemma between two options deemed unacceptable: severely curtail our explanatory practices with respect to macro events, or revise our conception of the essence of chance. He maintains, however, that we can escape this dilemma by making a distinction between ‘plain’ why-questions of the simple form ‘Why did D occur?’ and ‘contrastive’ why-questions of the more complex form ‘Why did E occur rather than E*?’ I will argue that even if a chance event receives a nontrivial explanation, there is still a sense in which it happens for no reason if there is a time prior to its occurrence at which the change of its happening when it does is fixed.