Janet Sidaway argues that the originality of Hilary of Poitiers's De trinitate rests with his novel interpretation of how believers ‘become God’. Hilary emphasises Christ's perfect human nature as the means of the believer's transformation or glorification. The word used by Sidaway to describe this process is anthropophany. Becoming God, deification, means that believers progressively become the perfect human that they were intended to be. Sidaway demonstrates this by showing Hilary's use of the exchange formula, which she expresses in the more familiar words of Gregory of Nazianzus and Irenaeus/Athanasius: ‘the unassumed is the unhealed’ and ‘God became man so man could become God’. Hilary linked these two phrases of the formula with his original exegesis of Philippians ii.6–8, 1 Corinthians xv.24–8 and the Transfiguration, as especially seen in book xi of De trinitate. The Fatherhood of God secures the coequality of the Son and the brotherhood of Christ secures our identity with him. Believers ‘become God’ by sharing in the glorified human body of the ascended Christ and collectively become the Kingdom of God returned to God, who becomes ‘all in all’. Sidaway further argues that Hilary has cleverly embedded the notion of progress (profectus) into the very structure, imagery, vocabulary and style of De trinitate. For Sidaway the autobiographical narrative in book i introduces Hilary as a spiritual ‘Everyman’, leading the reader through difficult theological arguments in the ‘carefully crafted progression of the whole twelve books of De trinitate’ (p. 23). In other words, Hilary is both author and actor, progressively explaining and exhibiting our anthropophany throughout De trinitate. Sidaway's reading of De trinitate book xi and her explanation of Hilary's understanding of deification is convincing and complements other scholarship on Hilary's Christology (Burns, Ladaria, Scully among others). I am less convinced by her claim that De trinitate is ‘not in fact about the Trinity per se’ (p. 7) but is rather a carefully crafted twelve books on the transformation of the believer. Sidaway exhibits a broad knowledge of the scholarship on Hilary and acknowledges the long-standing scholarly debates on the structure of De trinitate. Since we know that Hilary combined two distinct works to form De trinitate, and revised his early books in light of his mature pro-Nicene theology, more needs to be said about the structure of De trinitate if we are to believe that Hilary wrote these twelve books to explain and exhibit our anthropophany.