Aquinas on the Impossibility of Sin in Dreams

Abstract In this article, I discuss how Aquinas weaves together several sources to argue that dreams can never be sinful, although their causes may be. While asleep, no sin can occur because reason cannot function, and reason cannot function because the senses are impeded. I then consider why his treatment of dreams differs from his typical treatment of the effects of sinful acts, which he generally holds to be culpable even if they are not voluntary in their own right. I argue that the relevant difference is that weakening of reason in sleep, a necessary condition of dreaming, is natural rather than voluntary.