A conversation with Jack Tannous (Princeton University) about the "simple believers" who made up the majority of the population of Byzantium (as well as the caliphate and just about any premodern monotheistic society). They probably knew little about the minutiae of theology, but what did they know about their faith, and how important was theology for their religious identity? The discussion is based on Jack's recent book The Making of the Medieval Middle East: Religion, Society, and Simple Believers (Princeton University Press, 2018), which highlights the role of religious practice and interpersonal attachments.