This chapter will analyse the conception of mental disorders (i.e. illnesses that mainly affect rationality, the emotional sphere, and behaviour), as it emerges from Hildegard of Bingen’s Cause et cure. Mental disorders, in fact, serve as a touchstone for understanding the close connection between mind and body in medieval thought. The first two sections will be devoted to the causes and treatments of mental disorders; this analysis will reveal that the body defines the individual through its physical and psychic characteristics. The final section will examine the moral implications of this anthropological perspective: it appears to stand in contrast with the morality and spirituality of the time which—as also attested by Cause et cure—is based on a dualism between soul and body and exhort the soul to restrain the body.