Grant Macaskill's Union with Christ in the New Testament is a very good book. While attentive to the ‘dizzying range of potentially conflicting ways in which union with Christ is understood’ within the New Testament, Macaskill presents a strong case that ‘what we encounter in the New Testament is a remarkably cohesive portrayal of the union of human beings and God’ (p. 1). He arrives at this conclusion through a careful coordination of historical and theological modes of scriptural interpretation, and in conversation with some of the church's best reflection on this theme, especially as it emerges in Orthodox, Lutheran and Reformed thought.

Macaskill divides the book into two parts: a preliminary section (chapters 1–5) which sets up his examination of participation in the New Testament (chapters 6–11). In the first section, he surveys a massive amount of material: recent scholarship on participation in Paul (chapter 1); Greek patristic and modern Orthodox theologies of deification (chapter 2); Reformed and Lutheran accounts of participation (chapter 3); Jewish thinking which bears upon the interpretation of participation in the New Testament – e.g. corporate identity, glory language, mystical and apocalyptic traditions, messianism, temple imagery, speculation about Adam (chapters 4 and 5). While this section is mostly a report on relevant scholarship, Macaskill occasionally weighs in on issues which bear significantly upon his own construal of participation. To mention just a few examples, his determination to clarify the meaning of union with Christ with as much precision as possible leads him to caution anyone who would use the term theosis to describe the thought of a New Testament writer, since, when used in vague and uninformed ways, the term invariably obscures rather than illuminates the text. Macaskill is heavily critical of Michael Gorman on this point. Likewise, Macaskill rejects the idea of a widespread myth of Adamic glory within Second Temple Judaism which supposedly informs New Testament thinking – not only because he thinks we lack the evidence to support such a claim, but also because it implies that the glory that believers share in union with Christ is a ‘restored native property. . . a quality of a human being’, rather than ‘a divine attribute that is shared relationally with humanity’ (p. 143). The latter interpretation emerges as a key feature of Macaskill's own construal of participation in the second half of the book. Finally, his broadly Reformed emphasis on covenant as the organising framework within which the New Testament describes union with Christ leads him to reject the way that ‘apocalyptic’ readings of Paul (Käsemann, Martyn, etc.) tend to set eschatology in opposition to Torah observance, rather than seeing the latter as ‘taken up into’ the former (p. 116). Macaskill covers a vast amount of ground in this section, and while it is not always clear how his interaction with key figures in the tradition informs his own interpretation in the second half of the book, his treatment of the material is invariably clear, fair and judicious, and it provides a solid and illuminating foundation for his careful exegetical-theological work.

I will leave it to specialists to evaluate Macaskill's exegetical decisions in the second section, but I was especially impressed with his ability to lift up the distinctive voices within the New Testament while making a strong case for a broad coherence among them. As in the first section, the scope of Macaskill's discussion is vast. He devotes chapters to the body of Christ and temple imagery (chapters 6 and 7); the sacraments of baptism and the Lord's Supper (chapter 8); and participatory themes in the Pauline letters (chapter 9); the Johannine literature (chapter 10); and elsewhere in the New Testament (chapter 11). Macaskill synthesises the findings of the previous chapters in the conclusion, and in the introduction he provides a helpful summary of his overall argument in the second half of the book. If I were Macaskill, I would want anyone reviewing the book to quote this passage, so I will.

The book is full of additional strengths which I haven't mentioned, but none greater than Macaskill's desire to root our understanding of participation in Christ in what he calls the ‘ontology of the incarnation’ (p. 8). He repeats this point throughout the work, and yet when he finally arrives at his discussion of ‘Ontology, Incarnation, and Trinity’ in the conclusion, his treatment is a disappointingly thin one-and-a-half pages. As Macaskill continues to develop this aspect of his thought, he would profit from a serious engagement with Karl Barth's innovative covenantal-historical christology (especially as he develops it in CD IV), since Barth's translation of the two-natures doctrine into the sphere of a unified history is better suited to Macaskill's own purposes than the more classical two-natures doctrine which he seems to presuppose – one in which the meaning of the terms deity, humanity, person, nature and union, rather than being strictly defined by God's self-revelation in Christ, proceed from a less thoroughly covenantal theological imagination.