Abstract

This paper develops a modification of the notion of incommensurable worlds upon which Dreyfus and Spinosa base their robust realism. In particular, I argue that we cannot make sense of a conception of incommensurability according to which incommensurable worlds entail cognitively incompatible claims. Instead, as Dreyfus and Spinosa sometimes suggest, incommensurable worlds should be understood as being practically incompatible, meaning that the inhabitants of one world cannot, given their practices for dealing with some things, engage in practices central to the other world. Practical incompatibility grounds a defensible account of incommensurability while securing a necessary step in Dreyfus and Spinosa's argument for robust realism. At the same time, it shows how their idea of incommensurability is immune to the sorts of objections Donald Davidson makes to the idea of a plurality of conceptual schemes, without at the same time refuting Davidson's argument. Finally, an appreciation of the failings of cognitive accounts of incommensurability demonstrates that Dreyfus and Spinosa are not entitled to deny that all true descriptions of the universe are compatible.