 The author is grateful for helpful comments on various earlier drafts from Julian Cole, Mauro Corneli, Salvatore Florio, Teresa Kouri, Lisa Shabel, Stewart Shapiro, Matthew Souba and Ed Zalta. Thanks are owed especially to John MacFarlane, who provided detailed, insightful and helpful refereeing comments on later but still ancestral drafts. The author is solely responsible for any defects that remain.