Development of the faculty of spiritual discernment was one of the principal desiderata for the budding monastic of the early Egyptian desert. Anthony Rich has delved deeply into some of the key sources in order to present a thorough study of this theme. Rich sees substantial continuity between the New Testament's ‘discernment of spirits’ and the later monastic ‘discernment of thoughts’ – more so than many other commentators. The study focuses on two of the chief theorists of ascetic discernment, Evagrius of Pontus and John Cassian, together with the more pithy and practical depiction of discernment in the Apophthegmata patrum. Origen also gets a look-in as an important background figure. There appears, from this study, to be no real disjunction between the theorists and practitioners in the matter of discernment. Of course Origen, Evagrius and Cassian are in some ways of a piece, with the latter two having direct experience of the Egyptian desert in its heyday. It seems to this reviewer that the study would have greatly benefitted from even a brief exploration of alternative takes on discernment in, for example, the Cappadocian Fathers, the Syriac tradition or Macarius-Symeon (pseudo-Macarius). It is not entirely clear from this volume in what manner the specifically Egyptian take on διάκρισις is distinctive. Moving to specific points, I am puzzled by the repeated affirmation that Origen is deeply influenced by Neo-Platonism in general and Plotinus in particular. The supposition of such influence poses problems both conceptual and chronological. What Rich takes (on p. 28) as ‘Neo-Platonic’ doctrines that influenced Origen (such as divine incorporeity, transcendence, unity, goodness) have nothing specifically Neo-Platonic about them. And it remains unexplained precisely how Origen was so influenced by his younger contemporary. Mark Edwards's testy but deeply illuminating Origen against Plato (Farnham 2002) would have been a useful addition to the bibliography. Also puzzling is the use (p. 131) of the non-Egyptian writings of Macarius-Symeon as a witness to the teaching of the Egyptian desert. This is a confusion also evident in the bibliography where unimpeachable sources relating to Macarius of Egypt are listed under ‘Pseudo-Macarius’. (Conversely, the index distinguishes between ‘Basil the Great’ and ‘Basil of Caesarea’ – who were most certainly one person.) The list of such slips might be significantly extended. This work would certainly have benefitted from closer proof-reading and, more important, from some significant pruning and expansion by comparison with its previous incarnation as a doctoral thesis. But what it does, it does well. Rich has, in short, provided a very valuable resource that certainly enhances our knowledge of this indispensable component of the ascetic armoury.