 Thanks to Hakwan Lau and Susanna Siegel and especially Dave Chalmers who refereed the article. Special thanks to Mark Sprevak and David Barak for organizing discussion groups on the entry at the University of Edinburgh and at Columbia University respectively and for their feedback. Thanks to Jorge Morales and Doug Ruff for extensive feedback on central sections. Among many others, thanks for comments to: Jake Berger, Ned Block, Richard Brown, Alessandra Buccella, Denis Buehler, Tony Cheng, Mazviita Chirimuuta, Andy Clark, Sam Clarke, Carrie Figdor, Cressida Gaukroger, Michelle Liu, Chris Mole, John Morrison, Will Nalls, David Papineau, David Rosenthal, Ian Phillips, Adina Roskies, Forrest Schreick, Nick Shea, and Cecily Whiteley.