Volume 2, 1999
Metaphysics
Philip Percival
Pages 105-122
The Explanation of Chance Events
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.