In his book Religion within the Boundaries of Mere Reason, Kant presents his thesis that human nature is “radically evil.”2 To be radically evil is to have a corrupted moral orientation or, equivalently, an evil disposition. However, the very coherency of Kant’s radical evil thesis has often been questioned, as has the nature of the argument Kant supposedly offers for this thesis. Kant’s argument for radical evil consists primarily of two parts: an evil disposition derivation, where Kant argues that from a single evil maxim one can infer an evil disposition, and the universality claim, where Kant argues that all humans have an evil disposition. The first but not second of these arguments succeeds. Even so, radical evil is likely to be very widespread, if not universally so, among humanity. As such, Kant’s thesis deserves to be taken seriously by any moral and political theory. It deserves to be taken seriously, or so I shall argue, because it paints an eminently plausible picture of the human moral condition.