Joshua Hollmann has given us an ambitious and intriguing study of Nicholas of Cusa’s De pace fidei (1453). This dialogue, written after the fall of Constantinople, recounts a “vision” of a heavenly council, where wise men of the world’s nations and faiths seek peace, guided by Cusanus’s formula, “one religion in a variety of rites” (6). Because Christians, Jews, Muslims, and others share a common religion, their different rites should not lead to bloody conflict. As the council “focuses on the inner relationship between Christianity and Islam” (62), Christology becomes the core dividing issue (152). Yet for Nicholas, the Gospels and Qur’an “affirm Jesus as the Word of God” (190)—a shared affirmation that grounds Cusanus’s search for peace.

Whereas scholars often view De pace fidei as a rough-hewn, occasional piece, Hollmann sees it as “a creative synthesis of Cusanus’s cosmology, political theory, mystical theology, and Christocentric approach to Islam” (225). Chapter 2 links the dialogue’s topics of discussion to Thomas Aquinas’s Summa theologiae, moving from the one God, to the Trinity, creation, the Incarnation, the economy of salvation, and the Church—all via the divine Word. Chapter 3 parallels Bonaventure and Pseudo-Dionysius’s hierarchical schemes with De pace fidei’s sequence of speakers: the divine Word, saints Peter and Paul, philosophers, and the representatives of the world’s religions (88). Hierarchy yields gradations among faith traditions. Christians and Muslims’ “common adherence” to the Word unites them in one religion, while “the practices or rites of Christianity are nearer the One or God … than the rites of Islam” (135–36).

Chapters 4 and 5 address more practical issues, including the question, “How could Cusanus and [Pope] Pius II propose peace and preach crusade?” (125). There are clear analyses of irenic texts: Pius’s letter (perhaps unsent) to the Ottoman ruler Mehmed II, and Cusanus’s Letter to John of Segovia planning a conference of Christians and Muslims. Yet Hollmann comments that “perspective matters,” as De pace fidei’s dialogue “in the heaven of reason” aims to enlighten “those below … stuck in the tangled web of religious misunderstanding and persecution” (138). When dialogue fails here below, crusade becomes necessary (141). We may add that Cusanus became increasingly critical of Islam as he moved from the sanguine De pace fidei to his critique of the Qur’an in Cribratio Alkorani (1461), and finally to crusade. Hollmann also traces Nicholas’s view of the pope as Christ’s “supreme earthly representative” (176). De concordantia catholica (1433–34) envisions a universal church council where the pope presides, and Cusanus’s concern for church unity fueled his turn from the fractious Council of Basel to Pope Eugenius IV and the council seeking union with the Greek church at Ferrara-Florence. But it invites controversy to extend Nicholas’s “predilection for real and imagined councils … chaired by the pope” to Christian-Muslim dialogue (172). For Cusanus’s correspondence with John of Segovia recommends sending secular princes—not clerics—as Christian representatives to dialogue with Muslims; and De pace fidei does not mention church offices, which are thus among the various rites rather than essential to the unifying religion.

Chapter 6 examines parallels among Nicholas’s works. For example, De pace fidei expands De docta ignorantia’s conception of the church “to embrace all religious rites in a single universal religion” linked through the incarnate Word (185). Both De pace fidei and the Cribratio Alkorani, Nicholas’s analysis of the Qur’an, make Christology central to Christian-Muslim dialogue. Indeed, for Cusanus “one studies the Qur’an to study Christ” (190). Chapter 7 summarizes the book’s patristic background and emphasizes De pace fidei’s goal as ending “global schism through conciliar and Christocentric dialogue” (202). Hollmann responds to critics like von Balthasar, and he ends with a moving comparison between Cusanus and Thomas Merton as two mystics engaged in interreligious dialogue.

The Religious Concordance’s achievement is to highlight, through the lens of De pace fidei, the centrality of Cusanus’s Christology throughout his works and career. It thereby illuminates De pace fidei and its contexts—theological, historical, and political—and helps us to see Cusanus whole. Yet the book’s synthesizing focus occasionally makes Nicholas appear more consistent than he was, as in overemphasizing the papacy’s role in Christian-Muslim dialogue. More importantly, Hollmann invites us to follow Nicholas’s lead and reform our thinking about Islam and interreligious dialogue.