In this lecture, Professor Mazzotta introduces Purgatory and proceeds with a close reading of Cantos I and II. The topography of Mount Purgatory is described, and the moral system it structures is contrasted with that of Hell. Dante’s paradoxical choice of Cato, a pagan suicide, as guardian to the entrance of Purgatory ushers in a discussion of freedom from the standpoint of classical antiquity, on the one hand, and Judaism, on the other. In his refusal to be enslaved by the past, both on earth and in the afterlife, Cato is seen to embody the virtues of exile, setting an example for the penitent souls of Ante-purgatory (Purgatory II), including the pilgrim, who still clings to the comforts of the past.