Barrett and others have used Lewis-style evolutionary games to argue that we ought not to trust our scientific languages to inform us about ontology. More specifically, Barrett has shown that in some simple evolutionary contexts the best descriptive languages need not cut nature at its joints, that they may guide action as successfully as possible while simultaneously being deeply conventional. The present article expands upon Barrett’s argument, exploring the space for conventionalism in more metaphysically robust causal evolutionary models. By using (...) evolutionary prediction games, the present article examines the range of metaphysical facts in these models and shows how Barrett’s sceptical argument may be both challenged and expanded to cover these systems, resulting in a more thoroughgoing scepticism about what metaphysical conclusions may be drawn from linguistic and theoretical structure. (shrink)