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.