Few have shaped monastic spirituality more powerfully than John Cassian (c. 360–c. 435). Fluent in both Greek and Latin, the widely travelled Cassian did much to translate the legacy of Egyptian monasticism to the west. After extended stays in Palestine, Egypt, Constantinople and Rome, Cassian settled in Marseilles where he authored two classics: the Institutes, which outline rhythms of monastic prayer and passes on Evagrius' famed analysis of the eight deadly vices; and the Conferences, which claims to record twenty-four conversations with leading Egyptian masters. Benedict in his Rule commended both works, and thus Cassian became required reading for medieval monks. Despite this, Cassian's reputation as a theologian has suffered on various scores. One came from his supposed opposition to Augustine. In Conference xiii, Cassian, writing under the persona of a desert Father, explores the interworkings of grace and free will and, along the way, takes a few well-aimed jabs at Augustinian views. One of Cassian's colleagues in Marseilles, Prosper of Aquitaine, wrote to Augustine, complaining that locals were grumbling about his stark views on grace. This prompted Augustine's two most uncompromising treatises, On the predestination of the saints and On the grace of perseverance. Prosper himself launched a direct attack on Cassian in his Against the Conferencer. This squabble has been characterised since the seventeenth century as the opening salvo of the ‘Semipelagian controversy’. Patristic scholars have long insisted that this terminology is a serious misnomer and distorts Cassian's intentions and theology. Still, the prejudice survives, and so in this recent study Casiday seeks to redress Cassian's damaged reputation, claiming to offer ‘the first sustained attempt at re-reading Cassian's works without deference to the categories of outdated polemics’ (p. vii), to liberate him from the ‘rack of anachronism’ (p. 16).

Chapter i analyses Prosper's claims, contrasting them with assessments from Vincent of Lerins and Faustus of Riez. Casiday is unsparing and unrelenting in his polemic against Prosper, branding him as ‘totally unreliable,’ even ‘paranoid’ (pp. 22, 28–9). One has to ask whether ad hominems of this sort really advance our understanding. Casiday insists – rightly – that Vincent and other ‘Provençal masters’ (a term he argues for against the common but opprobrious ‘Semipelagian’) saw Augustine as ‘an author worthy of respect not uncritical devotion’ (p. 39). Casiday's strongest chapter is the second, in which he sets out a sympathetic account of Cassian's views on grace, noting that the real target of Conference xiii was not Augustine, but the Pelagians. He rightly insists that Pelagianism was no ‘theological monolith’, but a diversity of voices; so too was its opposition. Cassian's desert formation provided ample resources to reject Pelagianism, and his views, while they differ from those of Augustine, were wholly on the side of grace. Later chapters explore Cassian's roots in the desert tradition and his theology of prayer. At the close, Casiday examines the much neglected and rather maligned On the incarnation, against Nestorius. He demonstrates its links to Cassian's wider corpus and argues that it represents ‘not the last rambling work of an unwell old man’ but ‘the last creative outpouring of a prolific author’ (pp. 252–3). To make this argument, he dismisses previous interpreters, notably Aloys Grillmeier, whose analysis Casiday characterises as ‘more truculent than learned’ (p. 228). This study, while valuable in many ways, is itself quite truculent – repeatedly and, I believe, unnecessarily. Revising historical judgements is a demanding and intensely valuable task. I believe that it can be carried out with less polemics and greater civility.