Joseph Keim Campbell is Associate Professor in the Department of Philosophy at Washington State University. Michael O'Rourke is Professor in the Department of Philosophy at the University of Idaho. Harry S. Silverstein is Professor Emeritus in the Department of Philosophy at Washington State University. Campbell, O'Rourke, and Silverstein are coeditors of three previous volumes in the Topics in Contemporary Philosophy series, Causation and Explanation (2007), Knowledge and Skepticism (2010), and Time and Identity (2010), all published by the MIT Press.