Gregory Nazianzen's doctrine of the Trinity has had a most unusual reception in modern times. Since the Council of Chalcedon in 451 Gregory has been honored with the title “the Theologian” for his definitive teaching on the Trinity in the late-fourth century. His influence was then strongly felt in the christological developments that continued through the eighth century, and his stature in Greek Christian tradition is comparable only to that of Augustine in the West, although his influence is felt there as well. Yet despite his acknowledged ecumenical significance, Gregory's theological achievement has often eluded modern patristic scholars and systematic theologians. Even the most recent wave of specialized work on Gregory and the current synoptic studies of patristic doctrine have tended to overlook major aspects of his work. One of the most acute points of confusion in current scholarship—and a matter of no little significance for Nicene theology—is Gregory's doctrine of divine causality and the monarchy of God the Father within the Trinity. The recent debate over this topic, I would suggest, reflects the extent to which Gregory's doctrine has yet to be assimilated in contemporary historical and systematic theology. In this article I will seek to clarify Gregory's doctrine of divine causality in light of its current reception and to give some indication of its wider significance.