Bridge-building is painstaking work. The conveners and participants of the Building Bridges Seminar know this well. Monotheism and Its Complexities: Christian and Muslim Perspectives is a record of the fifteenth session of this annual, invite-only gathering of some of the academy's most prominent and promising “scholar-believers” to engage in a “dialogue of theological exchange.” The goal is not to arrive at some broad consensus on the predetermined theme. Quite the contrary, their work is conceived as “an exercise in improving the quality of Christian-Muslim disagreement,” one whose ultimate aim is growing “solidarity-in-difference” (ix, xii). This orientation distinguishes the resulting volume from many other works dealing with Christian-Muslim dialogue.

The book begins with a list of the 2016 participants, a retrospective on the seminar's first fifteen years—which includes a primer on the Building Bridges methodology—and a brief introduction. Four major parts follow this preliminary material, each comprising a main essay by a Christian or Muslim and a shorter response by an interlocutor of the other tradition. Part 1 tackles “The Oneness of God in the Biblical Witness”; Part 2 follows with “The Oneness of God in the Qurʾān and Ḥadīth.” Part 3 concerns “Grappling with the Unity Question in the Elaboration of Christian Doctrine”; Part 4 follows with “Safeguarding Tawḥīd in the Elaboration of the Islamic Tradition.” The volume concludes with a reflection on the seminar experience behind these essays. This glimpse inside the discussions is truly fascinating, giving an intimate and lively sense of the issues at stake as well as the diversity of perspectives involved.

Given that the theme is monotheism, there is a real temptation to assume that all the “complexities” are on the Christian side. Indeed, as Christoph Schwöbel's essay on the evolution of trinitarian doctrine details so well, the “story” of the Trinity, to use the language of Martin Nguyen's response, grows more complex, even “unwieldy,” with each retelling (93). But the story of the Islamic Tawḥīd (the principle of God's unicity) isn't so simple either. To that point, Sajjad Rizvi's essay on “Theological Argumentation on Tawḥīd in Islam” is an especially helpful corrective, complexifying Muslim thinking about unity and multiplicity in relation to the divine. The attention he gives to Sufi and Shiite perspectives, in particular, underscores the crucial task of attending to internal diversity (i.e., between coreligionists) within the broader Christian-Muslim dialogue.

As I suggested previously, a focus on “difference” is, in a fundamental way, one of the most unique and important contributions of this volume. Rather than trying to downplay disagreements, participants of the Building Bridges Seminar put them squarely in the center of their conversations. This dialogical bravery yields rewards. As the responses to the main essays demonstrate, clarifying differences can improve understanding, not only understanding of the other tradition but also of one's own. It can sharpen one's thinking, raise new questions, and illuminate green vistas of theological inquiry. It can also reveal where the deep parallels really do lie (see, for example, Maria Massi Dakake's response to Richard Bauckham's essay).

Still, there are other, more tangible benefits to the sort of interreligious exchange modeled here. This is the solidarity part of “solidarity-in-difference.” Fifteen years of painstaking work has done more than construct a dialogue. It has made a community. This is a community bonded over productive disagreement, yes, but also “collegial generosity,” even friendship (xi). It's hard to miss the significance of this dynamic in the book's remarks on the underlying seminar experience (see the preface and concluding reflections). Carefully cultivated relational virtues such as hospitality, trust, care, and vulnerability form the real common ground upon which these scholar-believers meet. Ultimately, if theologizing together is meant to foster Christian-Muslim solidarity, then the Building Bridges Seminar shows us what it takes: generous, attentive, and, most importantly, sustained dialogical relationships. Accordingly, I see this volume as a valuable resource for graduate and upper-level undergraduate seminars on interreligious dialogue, comparative theology, and contemporary interfaith relations.