I discuss the role of translatability in philosophical justification. I begin by discussing and defending Thomas Reid’s account of the role that facts about comparative linguistics can play in philosophical justification. Reid believes that common sense offers a reliable but defeasible form of justification. We cannot know by introspection, however, which of our judgments belong to common sense. Judgments of common sense are universal, and so he argues that the strongest evidence that a judgment is a part of common sense is that it is to be found in all languages. For Reid, then, evidence that a certain distinction is to be found in all languages is evidence that the distinction is part of common sense rather than being a common local prejudice. From such a perspective, empirical work in comparative linguistics can play a defeasible justificatory role in philosophical arguments. I contrast Reid’s position with the more radical position of defenders of the Natural Semantic Metalanguage approach, such as Anna Wierzbicka, who argues that only judgments that are translatable into all natural languages are justifiable. I show how such a position is rooted in an implausible view, although one common among cognitive scientists and linguistics, about the nature of concepts, which does not allow for novel concepts.