Daria Spezzano offers us a comprehensive and thorough study of deification (or divinization) in the thought of St Thomas Aquinas. She consistently presents his doctrine of deification within the overall context of his understanding of the meaning of human life as a journey made by divine grace to beatitude, such that divinization is identified as the dynamic process by which we are brought to deiformity in the beatific vision. Following roughly but not slavishly the ordo doctrinae of the Summa Theologiae, she thus places ‘deification’ within a larger picture, which includes Aquinas's theology of the Trinity and the divine missions, creation, the imago Dei, grace, the virtues and the gifts of the Holy Spirit (principally charity and wisdom), Christ and his grace, divine adoption and the sacraments, showing how deification is at the intersection of all of these. Her carefully‐laid accounts of the divine ordinatio by which God manifests his goodness, the non‐competitive character of divine and human causality, and Aquinas's appropriation of the notion of participation in creation, helpfully prepare the reader for Aquinas's teaching on deification as a progressive participation in the divine nature.

Among the chief merits of Spezzano's book is that it clearly manifests for the reader the connections between all the different areas of Aquinas's theology, so that the reader can gain a rounded sense of this journey to heavenly beatitude. Admittedly Aquinas himself seems to have expected his students to be able to make these connections for themselves, holding in mind and applying what they had previously learned as they worked their way through the Summa, but Spezzano appreciates the fact that modern readers find themselves more in need of having the connections pointed out for them, and that only so can they appreciate the sweep of Aquinas's theological vision. One salient example of this is the doctrine of the Trinitarian missions in q. 43 of the Summa's Prima Pars, and that of the divine image in man in q. 93. Aquinas himself gives no explicit indication of the link to be made between the two questions, but Spezzano shows how the connection is one of cause and effect, where substantially the same teaching on the divinization of the creature is treated from the perspective of its divine cause in q. 43 and from the perspective of what is produced in the creature in q. 93 (and thereafter in the Secunda Pars).

While drawing on the Summa as the crowning achievement of Aquinas's theological career, Spezzano also makes significant use of others of his writings, especially the biblical commentaries. This contributes not only to a presentation of the increasing importance and careful interpretation of key Scriptural verses, such as 2 Peter 1:4 and Romans 5:5, but also another important feature of Spezzano's method, whereby she enables the reader to think through the developments in Aquinas's thinking that touch on deification, and so grasp his final thought more satisfyingly. Here she follows Joseph Wawrykow in building on Henri Bouillard's work on Aquinas's increasingly Augustinian views on the roles of human preparation and divine action in the reception of grace, and Bernard Lonergan's demonstration of Aquinas's increasing understanding of the role of the actual grace of the divine auxilium. In the course of Spezzano's book we find that Aquinas's thought matured as he reserved talk of ‘deiformity’ to the goal of ‘deification’ in the beatific vision, gave increasing attention to ‘participation’ in his arguments, specified the mode of causality of the divine persons in terms of processions of knowledge and will, developed a more dynamic account of the imago Dei in relation to its divine exemplar, attended in a more nuanced way to the distinction between image and likeness, focused Christ's ‘fullness of grace’ on his habitual grace, and emphasised less the juridical and more the participative aspect of our adoptive sonship.

I particularly found valuable Spezzano's attention the person and work of Christ in the later chapters of her book, where she draws especially on the Tertia Pars, for example, in regard to the relationship between Christ's Sonship and our adoptive sonship by grace, and to his reliance on the grace of divine auxilium. She also shows how Aquinas allows for our participation in the grace present in Christ's humanity by way of treating Christ's habitual grace as maximal, such that it could not increase: because Christ has such a fullness of grace (itself a participation in the divine nature), he is instrumentally the principle of our perfection in grace and our moral exemplar. However, although the same explanation of the causal role may be given to Christ's charity and his gift of wisdom (pp. 295–6), Spezzano seems to give the impression that exactly the same may hold for Christ's pre‐eminent light of glory and ours (p. 190). A comparison of q. 10, a. 4 ad 1 with q. 7, a. 12 ad 2 suggests that such a position may need some nuancing.

Finally, readers will doubtless be familiar with A. N. Williams's The Ground of Union, which compares deification in Aquinas and Palamas. How theologians of East and West differ on deification is a key question in ecumenical theology. May we hope that in a future study Spezzano will re‐address this important point of comparison in Aquinas and Palamas?