How can we understand God's revelation to us? Throughout the church's history, theologians have often answered this question by appealing to a doctrine of illumination whereby the Holy Spirit shapes our knowledge and understanding of Scripture. Without denying the role of the Holy Spirit or the cognitive role of illumination, Ike Miller casts a broader vision of divine illumination and its role in the Christian life. In his constructive approach, Miller argues for a fully trinitarian view of illumination that forms not just our intellect, but also appeals to the affections and encourages our ethical action. In order to develop this theology of illumination, Miller explores both Augustine's and Karl Barth's readings of the Gospel and Epistles of John, including Barth's previously untranslated lectures on the Gospel of John. In the light of his careful study of both the Johannine literature and the theologies of two giants from Christian history, Miller contends for a doctrine of illumination whereby we are enabled to know God and participate in Christ by the power of the Holy Spirit.