Adopting David Burrell's particularist approach to comparative theology as a model, Joshua Ralston enters into the modern debates around public law and political secularism in his impressive work, Law and the Rule of God: A Christian Engagement with Sharī’a. This, he maintains, will

Ralston's methodology aims to avoid two pitfalls: the first leans too heavily on the ‘heritage and legal apparatuses of secular liberalism’ (p. 38), while silencing the critiques of modernity that emerge from those of deep religious commitments; and the second, opposite tendency reinscribes the battle lines between dār al-Islām and Christendom by reasserting the ultimacy of religious commitment. Substantively, Ralston brings Christian debates on the relationship between the law, the gospel and the grounding of political authority into dialogue with classical Islamic critiques of Christianity and modern Islamic debates on the relationship between sharī’a, secularism and civil/state law.

In chapter 1 Ralston presents a convincing case that sharī’a has been caricatured and dismissed by wide strains in liberalism, secularism and Christianity in the West. He adds that Christian political theologians in the West have had almost nothing to say about Islamic political ethics. If Islam has been engaged at all, it either has been reduced to terrorism or religious violence or has been encountered on an overly theoretical or sociological level. In order to move beyond this muddle, Ralston suggests that ‘political theology become a form of comparative theology’ (p. 27), opening concrete dialogue with specific thinkers from other religious traditions on particular themes. The relatively young field of comparative theology, however, suffers from its own lacunae: there has been little to no work devoted to questions of political theology, law or power. Tucked into a footnote, he seems to use as his own model Jurgen Moltmänn's and Johan Baptist Metz's encounters with particular Jewish thinkers after the Shoah to rethink Christian theodicy. The theological method here moves from engagement with particular religious others to theological reconsideration of one's own tradition.

Chapter 2 analyses two contemporary Christian theo-political approaches to Islamic political ethics, one conciliatory (Hans Küng) and the other confrontational (John Milbank). Both approaches ‘view sharī’a as primarily a theo-political problem that must be either critiqued or ignored rather than actively engaged’ (p. 88). Ralston then turns his attention to the history of Muslim critiques of Christianity's accounts of law and their relationship to the emergence of political secularism, and suggests that Muslim critiques of Christian approaches to the law fail to appreciate the ways in which Christian understandings of the law ‘are refracted through an understanding of the gospel’ (p. 136).

And yet it is the work of chapters 4–6, the most constructive segment of the book, to take these Muslim critiques seriously through a deep reading of Christian treatments of law. While admitting that Justin Martyr, Thomas Aquinas and Martin Luther are susceptible to Muslim critiques, Ralston outlines a Barthian response that insists upon judging all law in light of Jesus Christ. His nuanced reading draws from Barth what helps his own constructive argument and moves beyond Barth to provide a robust account of a public theology of law that shares some commitments with certain aspects of classical, modern and contemporary Sunni Islamic thought.

Chapter 6, the most theologically interesting chapter in the book, builds a Christian account of law as the ‘site of provisional indirect witness to God's rule of justice’ (p. 269) that provides a framework for interpreting sharī’a's place in public life. He then turns to sharī’a's contested colonial and postcolonial history to complexify any contemporary treatment of this subject. This chapter could serve as a prolegomenon for his next book project.

Ralston's aims in this book are ambitious. His scope is broad. His learnedness impressive. His use of footnotes is commendable, signalling mastery of thorny issues in Christian and Muslim accounts of law and interreligious methodology. He is careful to circumscribe his argument, noting where he refrains from dipping into contested exegetical areas. He is refreshingly unapologetic about his own Protestant confessional commitments. If at points I think he does not give some thinkers their due, it is because he is trying to paint on such a large canvas. In chapter 1, for example, while his initial claims about Western Christian political thinkers’ inability to take on Islam in a sophisticated way is obviously true, his particular criticisms of Eric Gregory, Oliver O'Donovan, Jean Bethke Elshtain, on the one hand, and Kathryn Tanner, David Fergusson, Kristen Deede Johnson and Charles Mathewes on the other read as rushed and unfair. Ralston's own work reads as a supplement rather than a rejection of these thinkers.

Overall, Ralston's book serves as a fresh model for comparative theology, offering deep learning of the religious other on a particular issue in order to shed light on theological issues from one's home tradition. This book should be read by anyone interested in Muslim–Christian dialogue, especially graduate students in the field of comparative theology.