Why lewisians should love deterministic chance

David Lewis claimed that deterministic chance was impossible. But deterministic chance seems ubiquitous in casinos, in statistical mechanics, and in evolutionary theory. It would be best for Lewis’s metaphysics if, in spite of what he says, we could reconcile his core views with deterministic chance. In this chapter, the author briefly rebuts two Lewisian objections to deterministic chance. The first is that our world is indeterministic at the quantum level, and this lower-level indeterminism translates to indeterminism at higher levels. The chapter explains how deterministic chances are possible on a broadly Lewisian theory. It also explains how there can be deterministic chances that function as nomological magnitudes, guide credence, and arise in objectively chancy situations. It is true that the author’s deterministic chances are not time-indexed. It is also true that they do not exactly satisfy principles, proposed by Lewis and others in a broadly Lewisian tradition, that presuppose time-indexing.