This thesis seeks an orderly set of theological reflections on the declaration that “God is light” (1 Jn. 1:5). Such talk of divine light, this study argues, must begin with the doctrine of God, namely, with God’s light in se and his “shining forth” ad extra towards creatures in the darkness of sin and death. This work therefore follows a precise pathway in expounding this theme. Chapter 1 offers a brief survey of the historical and scriptural uses of the concept of light in order to fix its linguistic and conceptual boundaries. Chapter 2 seeks to reflect upon God’s light as the light of his own radiant triune identity, as well as offering a preliminary examination of God’s economic, covenantal shining forth to creatures. Chapter 3 gives a much more detailed rehearsal of this act of shining forth by an account of God’s light as manifest in the economy of his works with which he lovingly elects, reconciles, and illuminates creatures. Chapter 4 proposes that with the treatment of God’s shining forth there belongs a treatment of the light of the church called out of darkness, gathered into the “marvelous light” of God, and set to proclaiming the “excellencies” of God. Chapter 5 concludes this study by examining what bearing the reality of God’s shining forth as Father, Son, and Holy Spirit might have on the work and call of theology as an activity of the “illumined mind.”