Achille Varzi is Professor of Philosophy at Columbia University, New York (USA). A graduate of the University of Trento (Italy), he received his Ph.D. in philosophy from the University of Toronto (Canada). His main research interests are in logic and metaphysics. He is an editor of «The Journal of Philosophy», a subject editor of the Stanford Encyclopedia of Philosophy, and an associate or advisory editor of The Monist, Studia Logica, Synthese, Dialectica, The Review of Symbolic Logic, and other journals. He also writes for the general public and contributes regularly to several Italian newspapers.