What Chance Doesn't Know

Humean accounts of chance have a problem with undermining futures: they have to accept that some series of events are physically possible and have a nonzero chance but are inconsistent with the chances being what they are. This contradicts basic platitudes about chances and is inconsistent with plausible constraints on credences. We show how Humeans can avoid these contradictions by drawing on metaphysically impossible worlds that are, nevertheless, scientifically possible. The guiding idea is that chance “doesn't know” at least some of the metaphysical facts. Unlike previous approaches to undermining (e.g., Lewis (1994), Thau (1994), and Hall (1994)), our account is part of a unified solution to a variety of challenges that the Humean faces. And it connects more closely with the way we employ stochastic theories in scientific practice. But perhaps most importantly, the idea that chance doesn’t know metaphysical facts flows from the Humean conception of chance.