 For helpful comments on the whole or parts of this article, I am grateful to Matthew J. Brown, Jacob Busch, Arthur Fine, Gregory Frost-Arnold, David Harker, Christopher Hitchcock, Kareem Khalifa, Timothy D. Lyons, Ilkka Niiniluoto, Elliott Sober, Bas C. van Fraassen, and K. Brad Wray. For special assistance, many thanks are due to Jamee Elder, Alex Koo, and Dean Peters.