When I first saw the publication announcement for this book, I simply assumed that the Gregory of the title would be Gregory of Nazianzus, with whom Evagrius of Pontus had a brief association while both were in Constantinople. Such a collocation of authors in a book makes a certain amount of historical sense, especially when we take into account Evagrius' great reverence for this Gregory as his teacher. However, the Gregory of Corrigan's book is in fact Gregory of Nyssa-- something of a surprise to this reader and undoubtedly to others as well.
The most significant contribution of Corrigan's book is his move away from the view that Christian writers of late antiquity were for the most part syncretistic borrowers and adapters in their relationship with the Greco-Roman philosophical traditions. This has been the prevailing impression left by many studies of the Egyptian ascetic-monastic tradition, which has been viewed as arising almost sui generis from the life and minds of such as Antony and the Desert Fathers. More recent studies, however, have shown that the ascetics were more connected with the larger intellectual environment than was once thought. Here we have the studies of Samuel Rubenson on the letters of Antony, and for the Apophethegmata Lillian Larsen has shown that even the literary form has its immediate roots in the Classical and Greco-Roman apophthegmatic collections.  Corrigan has demonstrated that Evagrius and Gregory were active participants in advancing preceding philosophical thought in their new Christian environment, even as their pagan contemporaries were contributing in their own domains--essentially we are talking about a single philosophical culture in continuity with antiquity.
Corrigan divides his attention, and his chapters, in roughly equal measure between his two authors. The first three chapters are introductory in nature, covering biographical details (ch. 1), the fourth century intellectual and theological context (ch. 2), and a general outline of the anthropological views of the two writers. Ch. 4 is devoted to the notion of impassibility or purity of heart in Evagrius and Gregory. The following six chapters alternate between Evagrius and Gregory, pursuing the topics of the eight thoughts or "reasonings" in Evagrius (ch. 5), the fall of the intellect in Gregory (ch. 6); ch. 7 is concerned with the path of the gnostic stage of the Christian life for Evagrius and its import for his understanding of the mind/soul/body relation; ch. 8 takes a closer look at Gregory's anthropology; the last two chapters examine the highest states of Christian ascetical-mystical progress as these are understood by Evagrius and Gregory respectively. A final chapter offers a helpful summary of the conclusions that can be drawn from this study and some interesting suggestions for further study.
At several points in the book Corrigan offers his justification for treating Gregory of Nyssa and Evagrius of Pontus side by side. The real issues of their comparability seem to lie in Corrigan's contention that each represents some major trajectories of fourth century thought with each making a significant contribution in three particular areas--first, the introduction of a type of cognitive psychology applied to the ascetic life; second, the development of a Christian anthropology; and finally, the area of sacramental and mystical theology. In spite of some general similarities between the two writers, Evagrius and Gregory are not as comparable as Corrigan would have us believe. The reader might also wish that Corrigan had explored his insights in greater depth by treating his authors in separate books.
Nevertheless, Corrigan's book is important both in its original insights on a number of issues and also in moving the discussion into a different perspective. On the other hand, Corrigan raises some points that either need some further nuance or continued investigation. In the first chapter, Corrigan singles out Nitria as "an experimental form of monasticism" distinct from the common-life or cenobitic model of such as Pachomius (4). For the fourth century it is anachronistic to speak of any particular form of monasticism as normative--we are in a period of transition between a number of experiments in the organization of Christian ascetic life that would gradually lead to a variety of monastic institutional forms. For the fourth century, the communities of Pachomius, the semi-desert settlements of Nitria, Kellia, and Sketis, the ascetic fraternities of Basil and his family are all "experimental", while at the same time in the process of establishing an increasing number of institutional norms. Corrigan's characterization of Coptic monks as "illiterate" is similarly unnuanced, given what we now know about the variegated social demographics, levels of literacy, and the commonplace bilingualism of a great many Copts. The studies of Roger Bagnall and Ewa Wipszycka have greatly modified older views of the demographics of the ascetic-monastic enterprise in Egypt. 
In chapters 3-5, Corrigan addresses the problematic modern understanding of the soul/mind/body relationship in Evagrius and Gregory. He argues that for both his authors mind includes experience and feeling as fundamental to its proper function. Chapter 5 on the eight thoughts or "reasonings" is one of the most interesting and insightful, particular in Corrigan's examination of Evagrius' notion of mental representations and their role in the passions; as well as his discussion of the tripartite soul in Evagrius. When Corrigan treats the unusual vice of acedia in a rather lengthy discussion, I think he ultimately misses the real problem posed by acedia. Acedia can best be understood in terms of its consequence--commitment failure: the ascetic is tempted to give up, to leave his cell, to abandon his radical commitment. The thought of acedia may be multifaceted in its symptoms but they all point to this particular end. At another point in this chapter Corrigan makes a valiant attempt to understand the few brief references in Evagrius to the classification of the eight thoughts according to their degree of materiality or immateriality. Unfortunately, the references to this idea in Evagrius are few (TH 14; Refl. 44; 47; 8TH 1, 4-6) and it is difficult to see how this idea can be mapped onto the actual and multivariable psychological experiences of ascetics, such as those listed in the Antirrhetikos. In other words the theory in Evagrius is seminal at best, and was never clearly worked out in his mind. However, Corrigan's suggestions for understanding the theory are intriguing.
Corrigan covers an number of closely related issues in ch. 7, namely, the intelligible body, body-conception and self-knowledge, scientific cognition, the mind/soul-body relationship, the issue of transmigration, the spiritual senses, and Evagrian metaphysics. In the course of an all too brief study of these topics Corrigan draws heavily on the Great Letter and the Kephalaia Gnostika of Evagrius. This is important to the future direction of Evagrian studies which will have to reconsider these works more thoroughly in relation to the whole of Evagrian thought. Corrigan is here clearly pointing in the right direction.
Corrigan devotes ch. 9 to a study of prayer and mystical experience in Evagrius. While the discussion as a whole is one of the best in the secondary literature on Evagrius, it still falls short in one aspect. In arguing against the mistaken scholarly view of Evagrius as an intellectualist, he pushes a little too far in the direction of a universally holistic anthropology in Evagrius' thought. More particularly, Corrigan wants us to realize the expansive role of love for Evagrius and to this end Corrigan makes frequent reference to Praktikos 81 and 84, where Evagrius talks of love as the offspring of impassibility and the end of the practical life. On p. 159 Corrigan offers an interpretive paraphrase: "Impassibility gives birth to love: a joyful love for other concrete human beings and for God primarily." But when Evagrius comes to talk of contemplation and of theologia, he turns to the discourse of knowledge and not of love. To quote Praktikos 84 more fully: "The end of the practical life is love, of knowledge theology." Evagrius abandons the discourse of love for the discourse of knowledge when he comes to talk of the final goal of the gnostic. The final goal is knowledge of the Holy Trinity, not love of the Holy Trinity.
For the most part, I have restricted my comments to the Evagrian chapters of Corrigan's book, partly for reasons of brevity, but partly because Evagrius has been the least studied of the two authors and Corrigan has mapped out for us some important directions for the future of Evagrian studies. The chapters focusing on the thought of Gregory are similar in their significance and depth of insight. We could only wish that Corrigan had written two rather fuller studies instead of the one covering both writers.
1. Samuel Rubenson, The Letters of St. Antony: Monasticism and the Making of a Saint, Minneapolis: Fortress Press, 1995; Lillian I. Larsen, Pedagogical Parallels: Re-reading the Apophthegmata Patrum, Dissertation: Columbia University, 2006.
2. Roger Bagnall, Egypt in Late Antiquity, Princeton, NJ: Princeton University Press, 1996; Ewa Wipszycka, Moines et communautés monastiques en Égypte IVe-VIIIe, Journal of Juristic Papyrology, Supplements no. 11. Warsaw: Uniwersytet Warszawski: Instytut Papirologii i Prawa Antycznego, 2009.