These are class sessions from Ideas of the Twentieth Century, Fall 2013, at the University of Texas at Austin.Professor Bonevac works mainly in metaphysics, philosophy of mathematics, semantics, and philosophical logic. His book Reduction in the Abstract Sciences received the Johnsonian Prize from The Journal of Philosophy. The author of five books and editor or co-editor of four others, Professor Bonevac's articles include "Against Conditional Obligation" (Noƻs), "Sellars v. the Given" (Philosophy and Phenomenological Research), "Reflection Without Equilibrium," (Journal of Philosophy), "Free Choice Permission Is Strong Permission" (Synthese, with Nicholas Asher), "The Conditional Fallacy," (Philosophical Review, with Josh Dever and David Sosa), "The Counterexample Fallacy" (Mind, also with Dever and Sosa), and "The Argument from Miracles" and "Two Theories of Analogical Predication" (Oxford Studies in the Philosophy of Religion). He was Chairman of the Department of Philosophy from 1991 to 2001.