When writers of the stature of Augustine provide explicit direction on how particular texts of theirs should be approached, it is always wise for readers to pay due attention to the guidance offered. Failure to do so will almost inevitably lead to distorted readings. In this major new work of Augustinian scholarship, a revision of his Oxford doctoral dissertation, Luigi Gioia offers a telling instance of the point, in relation to recent scholarly work on the De Trinitate.

In his first chapter, ‘Augustine and his Critics’, Gioia calls attention to the influential 1966 study of Augustine's trinitarian theology by Olivier Du Roy, with its conclusion that ‘Augustine handed over to the West a dogmatic pattern which tends to cut off the Trinity from the economy of salvation’. In his own work, Gioia aims to disprove the main thrust of Du Roy's study by demonstrating that it rests on a superficial acquaintance with the De Trinitate and a consequent assumption of the internal incoherence of the treatise, in contradiction of Augustine's own explicit statement to the contrary, in Letter 174. Taking as his starting-point important work by Rowan Williams and Lewis Ayres (whose own new study of the De Trinitate was not then out), Gioia proceeds on the presumption of the essential unity and coherence of the work as a whole. An immensely detailed examination of the whole text enables Gioia successfully to show that, for Augustine, the question of the identity of God the Trinity is inseparable from theological reflection on the way we know him, and that polarisation between the doctrine of the Trinity on the one hand, and the areas of Christology and soteriology on the other, reveals serious misunderstanding.

Gioia's approach enables him to uncover the coherence of the two halves of the treatise: the theological investigations of books 1–7 and the more explicitly epistemological focus of books 8–15. Gioia's analysis of the first seven books reveals the presence of two layers: an ‘outer’ layer corresponding to Augustine's formal topic, an exposition of the doctrine of the Trinity, and an ‘inner’ layer (where, according to Gioia, we perceive Augustine's real purpose in the work), which is a prolonged reflection on how human beings come to know God, by loving God through Christ. The two layers meet together, and their connection are explored, in the key fourth book, in the explicit identification between reconciliation and revelation. God reveals himself to us and reconciles us to himself through Christ. Gioia convincingly argues that Christ's role as Mediator and Redeemer is the bond of unity of the whole treatise. This is supported by its central place in the two pivotal books in the unfolding argument, book 4 and (for the second half of the work) book 13.

The epistemological implications of the earlier theological discussion are focused from book 8 onwards in an explication of the priority of love in the process of knowledge. Knowledge of God, in Christ and by the Holy Spirit, is restored to fallen humanity only through love. Gioia's lengthy concluding chapter, ‘The Image of God’, solidly confirms his unitive reading of the De Trinitate by showing how the dynamic, relational nature of God's image necessarily involves a movement towards the vision of God which is constituted by love.

Gioia has provided us with a stimulating work of lucid and detailed scholarship which will be required reading for all who wish seriously to grapple with Augustine's monumental, but too frequently either overlooked or misrepresented, treatise.