Recent years have seen a significant shift in Augustine scholarship: a movement to pay more attention to neglected texts in his dauntingly large corpus. Aided by the translation of previously unavailable texts into English, scholars are increasingly challenging the old commonplace that Augustine was not a systematic thinker and pointing out the complexity and depth of the theological views he expressed in his sermons, commentaries and less popular treatises. While Augustine typically wrote on an occasional basis, his thinking across multiple genres exhibits significant coherence and nuance, even as it often developed over time.

Adam Ployd capably advances this movement in this discussion of forty-one sermons Augustine preached in the course of a year. As Ployd convincingly argues, these sermons attacked the Donatists by suggesting that their schismatic view of the church is connected to a misapprehension not merely of the nature of baptism and martyrdom but of the triune God who is the hope of martyrs and the power behind baptism. Ployd advances his argument clearly and skilfully, situating Augustine in his intellectual milieu with opponents such as Cyprian and the Donatists and intellectual predecessors such as Ambrose and Hilary. He also puts Augustine in conversation with himself by drawing illuminating links to and distinctions from other works Augustine wrote. This is especially true of De Trinitate, whose influence Ployd seeks to decentre, following the ‘New Canon’ approach of Lewis Ayres and others.

Ployd's main thesis is that Augustine's sermons evince a ‘trinitarian ecclesiology’. Chapter 1 focuses on the church's pedagogical task of deepening knowledge and love of God. Augustine offers his hearers intellectual training by teaching them to distinguish between material and spiritual realities. In order for progress in knowledge to take place, progress in reorienting our desires must also occur. Augustine combines these themes by emphasising the virtue of humility, which the Donatists lack because they consider themselves morally and spiritually pure. The church, however, is composed of those who cling to Christ like a raft in order to be saved.

Chapter 2 reflects on the unity the church has as Christ's body. Sharing in the body of Christ makes it possible for Christians to know and love Christ in his divinity, and therefore to know and love the entire Trinity. Lovers of God should also love their neighbours, and here is where the Donatists fail. The church is meant to be a means of grace, not a club for the elite. Chapter 3 builds on these themes by reflecting on love, which the Spirit gives to the church. The Donatists’ failure of love, from Augustine's perspective, is a rejection of the source of love, the triune God. The Donatists thus fail to image God rightly, because they do not rightly imitate God's activity. The Trinity has a unique unity; Augustine even indicates that whenever scripture speaks of the Father and Son together the Spirit is implied. Ecclesial unity is weaker (not perichoretic) yet real because it is based in God's redemptive work in Christ and the giving of the Spirit.

Chapter 4 considers Augustine's view of baptism as expressive of and a basis for church unity. Baptism is an act accomplished by all three persons of the Trinity together; Augustine particularly speaks of Christ giving the Spirit. Bishops, by contrast, provide not the power of baptism but its administration. Bishops can therefore be imperfect while the baptism itself remains powerful. The power of baptism is a common work of the triune persons, whose actions are inseparable even if they are also characteristically referred to one or another person. These claims offer glimpses of the development of a theology of ecclesial participation in the divine life, but Ployd notes that Augustine does not develop a full version of such a theology in the sermons he surveys.

As Ployd is aware, his discussion broaches complex questions, some too briefly. His focus on Augustine's exegesis and its relation to his African and Roman interlocutors is illuminating, but only rarely allows readers insight into the Donatist perspective. It seems too quick to merely say that for Augustine the spiritually mature must distinguish the material from the spiritual; the import of Christ's body and the sacramental nature of created reality suggest that one need not simply move away from the material in order to find the spiritual (that makes Augustine too Platonist). It would have been helpful, too, to hear more about how separate or integrated love and knowledge are in Augustine's thought, and how they bear on one another. Ployd has, however, made an instructive and stimulating contribution to our understanding of Augustine's trinitarianism, the Donatist controversies and the complex unity of Augustine's thought. The themes he highlights suggest that the Donatist controversy quite naturally set the stage for aspects of the Pelagian controversies to come. And Ployd's discussion of Augustine's inspired exegesis of such biblical images as the oil dripping down from Aaron's beard (the Holy Spirit) and the moaning of doves (the cry of the sojourning church) would, alone, make his book worth reading.