Hilary of Poitiers (c300-368), Bishop and Theologian, was instrumental in shaping the development of pro-Nicene theology in the West. Carl Beckwith engages the extensive scholarship on the fourth-century Trinitarian debates and brings new light on the structure and chronology of Hilary'smonumental De Trinitate.There is a broad scholarly consensus that Hilary combined two separate theological works, a treatise on faith (De Fide) and a treatise against the 'Arians' (Adversus Arianos), to create De Trinitate. In spite of this the question of when and why Hilary performed this task has largely remainedunanswered. Beckwith addresses this puzzle, situating Hilary's De Trinitate in its historical and theological context and offering a close reading of his text. He demonstrates that Hilary made significant revisions to the early books of his treatise; revisions that he attempted to conceal from hisreaders in order to give the impression of a unified work on the Trinity.Beckwith argues that De Fide was written in 356 following Hilary's condemnation at the synod of Beziers and prior to receiving a decision on his exile from the Emperor. When Hilary arrived in exile, he wrote a second work, Adversus Arianos. Following the synod of Sirmium in 357 and his collaborationwith Basil of Ancyra in early 358, Hilary recast his efforts and began to write De Trinitate. He decided to incorporate his two earlier works, De Fide and Adversus Arianos, into this project. Toward that end, he returned to his earlier works and drastically revised their content by adding newprefaces and new theological and exegetical material to reflect his mature pro-Nicene theology. Beckwith provides a compelling case for the nature of these radical revisions, crucial textual alterations that have never before been acknowledged in the scholarship on De Trinitate.