Throughout his adult life Saint John Henry Cardinal Newman was fascinated by the controversies over the relations between Father, Son, and Spirit that exploded in the first decades of the fourth century, that led to the Council of Nicaea in AD 325, and that then divided the Christian world for decades afterwards. Newman’s explorations of the ways in which the church’s expressed doctrine of the Trinity emerged through these doctrinal battles forced him to rethink his understanding of how Scripture should be read, and were fundamental in his conversion to Catholicism. These essays offer new investigations of Newman’s methods, theories, and conclusions in honor of the 1700th anniversary of the Council of Nicaea, and show how his work remains vital for our own investigations of Christianity’s history and development. They were offered first at a symposium held at Mundelein Seminary in April 2024, a meeting made possible through the generous support of Jim and Mary Perry.