Dale Jacquette is Professor of Philosophy at the Pennsylvania State University. He is the author of Philosophy of Mind (1994), Meinongian Logic: The Semantics of Existence and Nonexistence (1996), Wittgenstein's Thought in Transition (1998), Symbolic Logic (2001), David Hume's Critique of Infinity (2001), and On Boole: Logic as Algebra (2001), as well as numerous articles on logic, metaphysics, philosophy of mind, and Wittgenstein. He is editor of Philosophy of Mathematics: An Anthology (Blackwell 2001) and Philosophy of Logic: An Anthology (Blackwell 2001).