The publication of this former doctoral thesis brings readers a welcome focus on Basil of Caesarea's letter collection. Silouan Fotineas treats philological issues and questions of attribution and chronology in his introduction; however, his main aim is to investigate how Basil used his correspondence to ‘foster communion’. He argues that the letters not only provide evidence of Basil's conception of ‘communion’ (koinōnia), but also that, for Basil, ‘the act of letter-writing was itself an instrument of communion’ (p. 8). After an introduction which helpfully sets Basil's letter-collection in the context of late antique letter-writing (including some fascinating comments on the function of the letter-carrier), the first part of the book sets out Basil's context, education and vocation, his theology and his ministry as bishop. The chapters in the second part focus more closely on the book's main argument and add more substantially to our understanding of Basil. In chapter iv, Silouan begins from a topos of the ancient letter-writing genre: that letters bring together those unable to meet face-to-face. His discussion of Basil's use of letters to bring about communion seems to assume that this is a theological and ecclesiastical extension of that purpose; however, this potentially very fruitful argument is not driven home very explicitly. Instead, the author turns to examples of how Basil used letters in doctrinal and ecclesiastical disputes and to a helpful analysis of Basil's use of the term koinōnia, including its metaphorical expression (as body, ship and garment). Theologically, the author relates koinonia firmly to Basil's Trinitarian theology, especially as it has been interpreted by theologians such as John Zizioulas. Practically speaking, communion is manifested in participation in the sacraments – especially the eucharist, but also baptism and repentance, as the author shows in chapter v. Crucially, the ‘head of each eucharistic community was Christ, who in each ecclesiastical diocese was made manifest through its presiding bishop’ (p. 245) and Silouan spells out the theological and practical implications of this very richly in chapter v/2. He also draws from Basil's letter-collection some fascinating observations about suffragan/assistant bishops (pp. 283–90). As a metropolitan, Basil acted in his correspondence to establish communion within his region of oversight, but also (as the author boldly puts it) aimed ‘to restore into the communion of the Nicene church all dioceses within the Eastern Roman Empire that were forced to conform to the Empire's non-Nicene legislation’ (p. 245). This broader function is examined in chapter vi, which stresses that, for Basil, ‘for every local diocese there was only one bishop’ (p. 297). The communion of the wider Church rested on the communion of each of these bishops with each other – and with the Nicene faith. For this reader, the strongest parts of this book are its contributions to our understanding of fourth-century conceptions of the vocation of a priest and bishop, both theologically and politically. The drawing out of a strongly theological dimension to Basil's understanding is an especially helpful complement to recent studies of Gregory of Nazianzus.