This study examines the role of theology in the biblical commentary of a fourth-century pastor and teacher. The notion that theology and scripture are inextricably connected in early Christian thinking has become a scholarly commonplace in contemporary patristic scholarship. But the nature of the connection has been less than clear, particularly with respect to the commentary on Psalms 1-50 (ca. 372) composed by Diodore of Tarsus (d. ca. 394). Despite the fact that Diodore identifies pronoia (providence) as the central doctrinal theme of the Psalms in his Prologue to the Commentary, scholars have largely overlooked Diodores engagement with pronoia in his exegesis of the Psalms. This study argues that a specific account of pronoia supplies Diodores primary theological framework for interpreting the Psalms by generating the questions he asks of the text and shaping his view of other themes in the Psalms. For Diodore, pronoia is more than a theme he identifies in the Psalms. Rather, the nature of God's pronoia is for Diodore the main doctrinal question posed by the Psalter, to which his exegesis of the Psalms provides the answer. That answer, then, is a view of pronoia which can be described as cooperative, reciprocal, and immanent.