The purpose of this study is twofold. First, it retrieves from obscurity Philoxenos of Mabbug, an influential figure in the religious politics of late antiquity whose place in the historiography has been eclipsed by his “heretical” status as a so-called “monophysite.” Secondly, and more importantly, this study uses Philoxenos' career to shed light on one of the most prominent but opaque moments of religious and political conflict in the late antique Mediterranean, the labyrinthine controversies over Christological orthodoxy. These disagreements over doctrines about Christ served as flashpoints in disputes between emperors, usurpers, bishops, monks, and laity for more than two centuries (c. 300-550 and beyond). While past treatments of these theological controversies have focused on the intellectual clash of the debate, this study explores ascetic, devotional, liturgical, and other contexts of praxis which gave the Christological arguments volatility and resonance. In particular, this work examines a half-century of controversy (c. 470-523) through a contextual study of Philoxenos’ life and work. It argues that a landscape of collective practice as well as opposing approaches to religious knowledge shaped his concerns over Christology and provided the firepower for his polemics. His involvement in these controversies played out within arenas such as the contingencies of episcopal administration, monastic contemplative practices, habits of scripture reading, liturgical rites including the Eucharist and baptism, and the routinized spiritual combat of the ascetic life. These shared activities of Christian praxis provided a context within which doctrinal disagreements emerged and took on meaning. Knowledge of God was a matter of both practice and theory. In sum, the definition of Christian orthodoxy was shaped by competing visions of Christian orthopraxy.