Two centuries after the rise of Islam, Christians in the Middle East had made considerable progress in formulating their beliefs in such ways that they became comprehensible – albeit not acceptable – to Muslims. In order to do so, they searched for common theological and philosophical concepts and terminology, and above all, for arguments with which they could defend their belief in a God whose dimensions exceeded the strict monotheistic conception of God in Islam. The three great Christian thinkers of the early ʿAbbasid period who are well-known for their experimentation with Christian apologetics in Arabic are Theodore Abū Qurra (d. c. 830), Abū Rāʾiṭa al-Takritī (d. c. 835) and ʿAmmār al-Baṣrī (d. c. 840). They belonged to different Christian traditions: Abū Qurra was a Melkite (i.e. Arab Chalcedonian); Abū Rāʾiṭa was a Syrian-Orthodox (“Jacobite”); and ʿAmmār al-Baṣrī belonged to the Church of the East (“Nestorian”). Although there are a number of detailed studies into the theology and apologetics of each of them, Sara Leila Husseini's lucidly structured book is new in that she compares their thought on the doctrine of the Trinity in detail. After a brief discussion of earlier Christian theologians’ approaches to Trinitarian theology, and a discussion of the early Muslim theologians’ thought on the unity of God, she proceeds with three tripartite chapters on each of the theologians, focusing on (a) their historical and intellectual background, (b) their theological explorations in which their discussions of the Trinity are embedded, and (c) their explanations of the doctrine of the Trinity. These chapters are followed by a second part, in which the methods of the three apologists are compared and discussed in more detail against the background of Islamic kalām of the same era, especially in the light of Muʿtazilī ideas.

Husseini discusses how each of these thinkers employed analogies from nature to explain that one can mean three without any sense of division. She also describes how they used biblical proof texts, despite the Muslim accusation of biblical corruption, and to a lesser extent the Quran. Most importantly, the apologists tapped into intra-Islamic debates on the attributes of God. Much of the study deals with the ways in which their engagement with contemporary Islamic kalām shaped their thought about Christian doctrine. The second part of the book is an attractive synthesis of the research into these three thinkers, who have been the subject of many studies in the recent decades (notably by Sidney Griffith, John Lamoreaux, Sandra Keating). Readers may want to concentrate on that comparative part, because it retells most of the discussions of the first part, but in a more compact and insightful way. It appears that ʿAmmār al-Baṣrī went farthest in formulating Trinitarian terminology along the lines of Muslim kalām, when he tried to argue that God's attributes of word and life are the Son and the Holy Spirit.

Although the author is somewhat hesitant about the matter in the early chapters, towards the end of her work she seems quite convinced that earlier scholars have wrongly interpreted the apologetic works as primarily intended for internal Christian consumption. She rightly argues that the works may also have been envisioned for Muslim readers and discussants. Yet, despite the close engagement with Muslim thought that she highlights, she seems to harbour a fixed conviction that these thinkers operated in the belief that Islamic and Christian doctrine are twain that shall never meet. Although this may have been the case, it is not known for a fact. Doctrines can evolve and the many doctrinal forms of early Christianity constitute proof of that. Moreover, Islamic theology was still very much in flux and it cannot be excluded that some Christians ultimately hoped to bring out the latent Trinitarian element from the Quran to kalām. The fact that the Muslim theologian Ibn Kullāb found himself in a grey area between the two religions may show that at times the borders between the two religions were not as sharply delineated as one might think a millennium down the line.

This book was originally a dissertation defended at the University of Birmingham in 2011. It has undergone a minimal round of corrections and was not bibliographically updated. Numerous inconsistencies and errors remain. The dreadful transliteration of Arabic leads to distracting guesswork on the part of the reader (p. 84 “bidha” = bihā (?); p. 126: “al-kalāqa” = al-khallāqa, p. 133: rawiyyat = ruʾya, p. 177 jamīaʿha = jamīʿuhā (?) etc.). Inconsistent referencing to the source material is confusing, with strange mixed forms such as the Risāla al-ūlā, where one would expect “The first letter” or al-Risāla al-ūlā, with Arabic and English titles mixed in one line (p. 192) or even given in French (!) (p. 120, n. 46). There are boundless infelicities and lacunae in the index and the bibliography as well. One might want to raise the question to editors and publishing houses as to what role they see for themselves, when their three-figure priced books contain the same poorly edited texts as those downloadable for free from a dissertation database.

Finally, it should be noted that any further studies on this topic need to take into account two further recent studies: Thomas W. Ricks's Early Arabic Christian Contributions to Trinitarian Theology (Minneapolis, 2013) and Najib G. Awad's Orthodoxy in Arabic Terms: A Study of Theodore Abu Qurrah's Theology in Its Islamic Context (Boston and Berlin, 2015).