Achille C. Varzi is Professor of Philosophy at Columbia University in the City of New York. 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, Synthese, Dialectica, The Review of Symbolic Logic, and other journals. He also writes for the general public and contributes regularly to several Italian newspapers, and is currently teaching at Taconic Correctional Facility within the framework of Columbia University’s Justice In-Education Initiative.