  Thanks to Ian Blaustein, Roger Crisp, Charles Griswold, Knud Haakonssen, James Harris, Colin Heydt, David McNaughton, Amelie Rorty, Daniel Star, and Bob Tennant for extremely helpful comments and suggestions. Thanks to Stephen Darwall for suggesting the article, to Ray Frey for initiating my interest in Butler, and to the students in my Butler seminar for helping me think through the issues discussed in the article.