This paper examines a set of questions concerning moralia in Peter of Abano's Expositio Problematum (1310) and shows that its author takes a naturalistic approach, heavily reliant on medical doctrine, to propose that not only the lower virtues, but also those dependent on the rational soul, are closely tied to physiological states. For the irrational soul, this close connection with the body is not surprising. However, in the case of the rational virtues, the dependence on the body is more unusual and offers a significant example of Peter's application of medical doctrine beyond the established bounds of the discipline. His is a very different approach to human virtue than that of his contemporaries, and it blurs the distinction between moral virtue and natural virtue throughout his exposition. At the same time, this commentary offers insight into Peter's broader position on the soul.