Using sources from the fourth century CE, Thomas E. Hunt analyses how people imagined breath in late antiquity. Breathing was a way to mark out and understand human difference in the complex social world of the late Roman Empire. In this context, a person’s breath was used to judge the quality of their social relationships. Breath also held cosmic import, for when a person drew in air they participated in the wider structure of the universe. Christian writers described the inner life of God by referring to these models of breath and breathing. In this essay, Hunt shows how social and theological accounts of breathy relation reinforced each other.