The outstanding importance of Augustine's De trinitate for western Trinitarian theology is beyond doubt. In its wake it provoked a constant stream of interpretations, the history of which is worthy to be a topic of scholarly interest on its own. In Augustins Trinitätsdenken Roland Kany presents an overview of research on De trinitate since the middle of the nineteenth century. With respect to the vast number of publications during this time he wants to clarify which results of the discussion are beyond dispute and which questions remain to be debated. Far from just reporting the status quo, Kany adds new observations and answers to old questions.

After two chapters on the text of De trinitate and its chronology the elaborate third chapter on ‘Sources, influences and adversaries’ reflects one of Kany's main interests: to root Augustine's Trinitarian theology firmly in the historic context of fourth-century theological debate. In detailed analysis of the pagan and Christian Greek and Latin sources Kany presents the broad spectrum of the discussion in which Augustine develops his arguments. The categories of ‘neoplatonism’ or ‘antiarianism’ prove to be far too unspecific to describe the many theological strands, arguments and schools that Augustine deals with.

It is no contradiction to say that Kany, while insisting on historic differentiation, judges the great interpretations of Augustine's Trinitarian theology according to whether or not they manage to integrate the many perspectives which are contained in the De trinitate. He shows the legitimate points of view that dominate the various interpretations, but insists that neither of them can be the interpretation of Augustine's thinking. The juxtaposition of theological and philosophical interpretations in particular has to be overcome in favour of a view that integrates both Augustine's interests.

Kany devotes two chapters to the theological and philosophical aspects of De trinitate. As before he insists on the precise context in which the theological concepts are developed, and has no patience with intellectual vagueness to make a concept fit for its theological use. On the other hand, he likewise notices shortcomings in philosophical literature on De trinitate that have links with the more biblical and theological parts of the book and consider them merely as decoration or detours away from the ‘hardcore philosophy’. Kany presents the richness of philosophical inspirations and themes that Augustine delivers and that has especially been rediscovered in recent scholarship after a time of neoscholastic dominance of Augustine. A chapter on Augustine's Trinitarian theology in his other works, including some informative pages on the legend of Augustine and the boy at the seashore, complete the discussion of Augustine's text.

The following chapters deal with the place of Augustine in the history of dogma. The works of F. Chr. Baur, A. von Harnack and Catholic authors are discussed insofar as their various conceptions of ‘history of dogma’ reflect on their interpretation of Augustine. In this context Kany deals with the old question of ‘Greek vs. Latin Trinitarian theology’ and the thesis connected with de Régnon. In his chapter on the ‘Wirkungsgeschichte’ of the De trinitate Kany not only presents, as might be expected, the western tradition, but also takes a look at Augustine's reception in the Churches of the east, though not much research has been done in this field.

To present the impact of Augustine's Trinitarian theology on contemporary theology, the theologies of Barth, Rahner, von Balthasar, Moltmann and Pannenberg and their criticisms of Augustine are discussed. For each of these very different authors De trinitate is the founding document for just that concept of Trinitarian theology that they want to overcome. In his metacritique Kany notices that these authors contradict themselves in their criticism of Augustine, and he takes this as an indication of the difficulty of the task, i.e. to overcome Augustine's approach. On the other hand he can show that some of contemporary criticism falls short of Augustine's reflections, because some of the assumed alternatives had already been discussed and dismissed by him.

Kany ends his book with a substantial chapter on ‘Augustine's original insight in De Trinitate’. Here he brings together the results of his previous chapters and tries to integrate them into a coherent interpretation. According to Kany the purpose of the first seven books of De trinitate is to reject false interpretations of the Trinitarian faith. The first four exegetical books are not, as was thought in neoscholastic tradition, a biblical proof of the dogma, but a discussion of false interpretations. Since the Arian and homoian adversaries of the Nicaean faith are as skilled in exegesis as are orthodox theologians, Augustine takes pains to show where those adversaries bring false interpretation of Scripture, and that the Nicaean faith can be demonstrated to be the result of a sound exegesis. Likewise books v–vii are not the precursors of the neoscholastic ‘formulation of the dogma’ or ‘proof from catholic tradition’, but a detailed review of theological approaches of his time and a discussion of their strengths and weaknesses. Augustine is honest enough not only to scrutinise opposing theories, but also Nicene and neoNicene theology, none of which satisfies his theological demands. It is this result that triggers the develeopment of his own approach, developed mainly in books viii–x. In short it is Kany's thesis that Augustine presents the threefold structure of the mind not only as an analogy of the divine Trinity, but as a true image insofar as the human mind is related to its divine origin. In books xi–xv Augustine elaborates and deepens this ‘original insight’ of his Trinitarian theology.

While the details of Kany's historical and systematic thesis may be subject to scholarly discussion, the outstanding value of his book is beyond doubt. Kany has meticulously gathered together the results of the last 150 years of research on Augustine's De trinitate. His book is overflowing with historical and theological information that will inspire every reader, scholar and student to start or to continue his or her own study of the great Father of the Church. The fifty-page bibliography alone is a most valuable starting point. Those who are not experts on the details of fourth-century Trinitarian theology and that of Augustine in particular, will find this book well-structured and full of profound information and hints for further studies.

For decades now Trinitarian theology has been gaining prominence among theological disciplines. Whether Augustine's thinking is accepted or criticised, the importance of his De trinitate will remain undiminished in future Trinitarian scholarship. With this excellent book Kany has set a benchmark for all further work in this field.