God’s Shining Forth offers a theological presentation of divine light in which the leading motif is the doctrine of the Trinity. More precisely, this study is organized around a double trinitarian theme: God is light in himself, and from himself God is radiant in relation to human creatures. This double affirmation is expounded by considering its extensions in the work of God’s grace, in ecclesiology, and in the nature of theological intelligence. The chosen conversation partners in this study are some of the leading pro-Nicene trinitarian theologians of the fourth century, plus John Calvin, Karl Barth, and a selection of contemporary authors. Andrew Hay argues that the scriptural statement God is light is best understood as a confession of the eternal, fully realized life of the triune God in its wholly gratuitous electing, reconciling, and illuminating human creatures in the darkness of sin and death.