This is an excellent introduction to the man, his times and his legacy, but much more than an introduction. The fruit of many years of study and writing about Irenaeus, it both reveals and invites a deep and sympathetic engagement with the thought of the great second-century theologian. The first section situates Irenaeus in his time and place, notes his connections in Rome, explores his relationship with Polycarp, and offers a chronology of his life and writings. The title of this section, ‘Irenaeus of Lyons: ambassador for peace, reconciliation, and toleration’, signals one of Behr's central contentions, as he states it in the conclusion:

Marcion, Behr observes, ‘broke from the common fellowship’ and the Valentinians ‘were already aware of the distance that separated themselves, as truly “spiritual”, from the lower “psychic” Christians of the other communities before Irenaeus intervened’ (p. 206). Moreover, it was Irenaeus who upheld and defended a diversity of practice among apostolic Christian communities. The second section, ‘Against the heresies’, guides the reader through the five books of Irenaeus' magnum opus, providing helpful outlines and summaries of each. Behr argues that the title that Irenaeus gave to his work, Refutation and overthrowal of knowledge falsely so-called, really describes only the first two books, probably the original scope of the project, and that the last three books are more a demonstration of the apostolic faith itself. Outside of book i (which is given over to the depiction of the heresies), the remaining four books are found to have the same threefold pattern of organisation: ‘one God (haer. 3.6–15; 4.1–19; 5.1–14), one Christ (haer. 3.16–21; 4.20–35; 5.15–24), the human being (haer. 3.21–3; 4.36–41; 5.25–36)’ (p. 121). In the third section, ‘The glory of God’, Behr summarides books 3–5, and then develops several major themes of Irenaean thought. Behr expertly illuminates the Irenaean emphasis on the majestic unity of God's plan from beginning to end. The fall into sin, though tragic, did not trigger a divine ‘plan B’: ‘death results from human action, but it is nevertheless a result that is subsumed and transformed within the larger arc of the economy, as it brings the creature made from mud to share in the very life, glory, and power of the Uncreated, so demonstrating the goodness and righteousness of God’ (p. 194). Finding the symphonic unity in God's complex and multifaceted plan displayed in Scripture is mirrored in Irenaeus' active ministry of bringing unity to a diverse and divided Church. Behr's book offers a fine and compelling treatment of Irenaeus and deserves a very wide audience.