García Mac Gaw argues that debates over baptism were really about defining ‘un ordonnancement topologique institutionnel’ (p. 111) in two very different political environments. In the mid-third century, Cyprian distinguished between those inside and outside the Church by denying the validity of heretical baptism. Augustine could ignore outsiders, focus on internal dispositions and treat baptism as a ‘“mécanisme” d'inclusion’ (p. 280). This book's structure resembles that of Attilio Carpin's Battezati nell'unica chiesa? (2007). Both are framed around the debate between Carthage and Rome at one end and Augustine salvaging Cyprian from the Donatists at the other. But the differences between them are significant. García Mac Gaw often eschews chronology, making this difficult reading for those not equally expert in theology and late Roman history. Yet García Mac Gaw, unlike Carpin, draws explicitly on the enormous body of scholarship pertinent to his subject; he not only cites but engages with it deeply on many points, which helps to explain why baptism, the book's ostensible subject, comes to the fore only at p. 123. By that point, however, García Mac Gaw has laid the groundwork for what makes his book so distinctive, important and rewarding. For Carpin, ‘la questione battesimale’ was always, at its heart, ‘certamente una questione di teologia sacramentaria’. But for García Mac Gaw, ‘Le discours théologique est alors un moyen, ou un instrument, sur lequel viennent s'appuyer les acteurs sociaux pour influer sur les positions de pouvoir ecclésiastique’ (p. 36). He is most successful by far at bringing Cyprian to life as a social actor possessed of ‘une habilité profonde et une fine perception du moment où il convient d'agir politiquement dans le champ institutionnel ecclésiastique’ (p. 109). So whereas his theology was sympathetic to Novatian's, politics made Cyprian side with Cornelius (p. 111); disagreement with Stephen over rebaptism was an effect, not cause, of political tensions between Rome and Africa (p. 131). García Mac Gaw is most compelling and persuasive in the details, as he analyses key texts and judiciously weighs prior arguments; the only omission that seems significant here is Ps.-Cyprian, De rebaptismate (see recently E. Ferguson, Baptism in the early Church [2009], 385–8). The section on Augustine is less convincing. In part, no doubt, this is because we know so very much more about the political context, yet it is here fitted uncomfortably into a hundred pages, which include the analysis of De baptismo. Discussion of the Firmus and Gildo revolts, which also involved tenuous alliances, help tie this section in with the first, but García Mac Gaw simply spends too little time with Augustine himself to balance the whole well (Hermanowicz's Possidius of Calama [2008], though, is a neat complement). Here also we notice some isolated but significant omissions in the bibliography: J. Patout Burns studied Augustine on Cyprian (in Augustine: from rhetor to theologian, 161–71); so did Vittorio Grossi in his La catechesi battesimale agli inizi del V secolo (1993), which shows that there are limits to how far one can comprehend Augustine's position on baptism without taking on Pelagianism. None the less, there is great virtue in García Mac Gaw's method that reveals careful deliberations, reluctant compromises and hard decisions in the debate over baptism – a ‘transformation interne’ (p. 282), less dramatic but more real and consequential than the idea of a Church Triumphant.