Book excerpt: Saint Gregory of Nazianzus stands as the founding father of the Byzantine religious synthesis, and his own conception of the vision of God as light made him an important figure for Byzantine spiritual writers. This study is a critical analysis of the man, his writings and inner life in the English language. It offers an insight into the mind of one of the greatest protagonists of Nicene theology and opens a window onto the world of late antiquity and the place of the Christian Church in it.