Thymos (or thumos), cognate with Indo-European words meaning “smoke,” is one of a number of terms in Greek which associate psychological activity with air and breath. In the Homeric poems, thymos is one of a family of terms associated with internal psychological process of thought, emotion, volition, and motivation. Though the range of the term’s applications in Homer is wide, that in itself gives us a sense of the unity of cognitive, affective, and desiderative processes in Homeric psychology. No post-Homeric author can rival that range, but something of the richness of the Homeric conception of thymos as an interrelated set of motivations re-emerges in Plato’s conception of the tripartite soul in the Republic and the Phaedrus. Plato’s thymos represents a pared-down model of human agency typified by one central desire or aim in life but also exhibiting whatever further capacities of persons are necessary to enable it to pursue that aim in interaction with the other elements of the personality. As in Homer, the metaphorical agency of Plato’s thymos does not detract from the notion of the individual as the real centre of agency.