John Cassian’s Nosology of the Soul

Abstract This chapter continues studies of Cassian while shifting focus from dreams to passions, or vices (vitia). Cassian develops Evagrius’ “eight wicked thoughts” into the “eight principal vices.” He experiments over the course of the Conferences with several ways of organizing these and other related vices, though he generally relies on taxonomic approaches that differentiate between genera (the principal vices) and species (more specific manifestations). Cassian’s approach is best contextualized against Evagrius and wider traditions of organizing passions, virtues, and vices, in lists. However, Cassian inflects his lists of vices through a diagnostic study of thoughts and strong emotions as exteriorizations of interior dispositions. Thus, he ultimately hangs the eight principal vices on the tripartite soul in a complex medical analogy that provides a stable nosology of passions, relating transient emotional states to biopsychosocial disorders in interior dispositions.