 Frances Howard-Snyder is grateful to Jonathan Bennett, Tom Downing, Dan Howard-Snyder, Hud Hudson, Phillip Montague, Alastair Norcross, John Hawthorne, Stuart Rachels and Kadri Vihvelin for comments on earlier drafts of the single-author entry on which this paper is based. She is also grateful to the Bureau for Faculty Research at Western Washington University for support while writing it. 