The Christian doctrine of ‘justification’, and especially ‘justification by faith’, is most closely associated with Paul in the first century and Luther in the sixteenth. Its Pauline formulation and Lutheran interpretation have been extensively studied, but if there was anything significant in between them, it has passed largely unnoticed. This is partly due to the influence of T. F. Torrance's little book on the Doctrine of Grace in the Apostolic Fathers (1959), in which he asserted that the doctrine of grace that Paul proclaimed did not survive into the apostolic era. Torrance owed the idea to Karl Barth, his Doktorvater, and Brian Arnold observes his significance in shaping subsequent discussion. While Arnold does not claim to be the first to critique this approach, he seeks to give the most sustained account yet of the ‘presence’ of the Pauline doctrine of justification in the apostolic fathers. His own study is organised by author, with a chapter each on 1 Clement, Ignatius, the Epistle to Diognetus, the Odes of Solomon and Justin's Dialogue with Trypho. Each chapter presents a brief introduction to the text and significant issues of studying it, such as date, provenance and transmission history. The main part of the chapter is then devoted to a close reading of the passages that Arnold finds most significant for his theme. A concluding chapter draws together the findings. In this way, Arnold charts the scope and shape of the doctrine of justification in this period.

Justification in the Second Century participates in a wider trend of growing interest in the second century. It succeeds in drawing attention to the challenge of studying pre-Lutheran concepts of justification, and in highlighting salient texts across a range of different types of second-century Christian literature. Arnold brings out the diversity of genres, doctrines and emphases in the different texts that he studies. 1 Clement says both that one is justified not by words but by works (1 Clem. 30.3) and that all alike are justified through faith (1 Clem. 32.4). Ignatius’ contribution is for the most part found to be only indirect, through his interpretation of love and perfection, as he mentions justification in a relevant way only once (Phld. 8.2). The Epistle to Diognetus, meanwhile, is explicit (Diog. 9.2–4). The Odes of Solomon stand out as a hymnic source for liturgical use, and include the line that ‘he justified me by his grace’ (Od. 29.5). Justin never names Paul, but he does cite Abraham as the type of justification by faith apart from works of the law (Dial. 23, 92). For a book that originated as a PhD thesis, Arnold's study is notably wide-ranging, thorough and well-written. However, it is the dreary duty of a reviewer also to note weaknesses.

In my view, the most significant issue lies in identifying the object of study, and its significance. Arnold poses the open-ended question, ‘how did the second century fathers understand the doctrine of justification?’ (p. 4), but in practice, he declines to be controlled by their use of terminology (dik- words), and instead seeks ‘conceptual links’ that suggest the ‘concept of justification’ (p. 5). However, the closest he comes to defining this ‘concept’ is a sentence on his first page, which describes the ‘traditional Lutheran reading of Paul … that justification is forensic, which means that the sinner is declared righteous in God's sight by faith and found not guilty of sin’ (p. 1). He does not allow himself to get drawn into the ‘quagmire of Pauline studies’ in order to explore Paul's own concept of justification, nor does he engage closely with Luther at first hand. To my mind, this leaves his study strangely etiolated. We repeatedly encounter a penumbra of terms that are widely associated with a Lutheran reading of Paul, such as ‘justification’, ‘justification by faith’, ‘grace’, ‘forensic justification’, ‘Pauline’, but there is no real grappling with Paul himself. Barclay's Paul and the Gift (2015), the most significant recent contribution to this debate, is not cited (cf. pp. 1–2, n. 4). Conversely, second-century authors are mined for passages that might show that the doctrine (whatever exactly it was) was ‘present’ in the second century. To my mind, this underplays questions of proportion: how much did this doctrine actually matter to these second-century authors, if they write of it so rarely and often ambiguously? In writing a history of doctrine, should we be focusing on what was ‘present’, or what was ‘significant’, and what is the relation between these?

The book is generally well-presented, but lengthier quotations from primary sources are given without the original language, and much significant information is relegated to lengthy footnotes.