Juan de Segovia (†1458) is a particularly intriguing character in the history of Muslim-Christian relations, since he has a foot in what are usually conceptualised as two different historical periods and two regions that are emblematic of Christian-Muslim encounters in the respective eras. As a native of the Iberian Peninsula whose education and early scholarly and political career took place at the University of Salamanca (1407–31), he represents the medieval encounter with Muslims in south-western Europe. As a later visitor and resident in more northern regions and, above all, as a contemporary to the Ottoman conquest of Constantinople in 1453, he is part of the early modern chapter of the history of Muslim-Christian encounters. On the one hand, he perpetuated early medieval and medieval polemical tropes in his writings about Islam and contributed to the missionising efforts that had gained momentum in the late medieval period. On the other, in his translation of the Qur'an, which he carried out in collaboration with the Muslim scholar Yça Gidelli, he seems to have taken the first steps towards the more philological perspective that we commonly associate with the Renaissance and later centuries. (Only the preface to this translation has come down to us.) Juan thus lends himself to a glimpse into a history of encounters between Christian western Europe and Islam that is not interrupted by chronological and geographical divisions. That is not to say that such distinctions should be effaced. The Andalusi and North African Islam of the twelfth century was, after all, very different from the Ottoman Islam of the fifteenth century, but Juan illustrates how much these might have been seen as manifestations of a homogeneous phenomenon. What makes Juan de Segovia an especially interesting figure is that he allows for insights into the fractured religious landscape of western Europe itself since he was part of the conciliar efforts, mostly in Basel where he was involved in negotiations with the Hussites.

The ambition of the book under consideration is to acknowledge Juan's thought and contribution to European intellectual history. While he is frequently mentioned by authors surveying Christian-Muslim relations, he has not received as much attention as other figures, notably Ramón Llull, Nicholas of Cusa and Aeneas Silvius Piccolomini. The book follows a chronological order, and while demonstrating how Juan responded to new experiences in his life, the author makes a case for intellectual continuity and consistency. The persuasive power of Scripture and his interest in converting Muslims can be traced back to his first writings, which consist of two lectures (repetitios) delivered in 1426 and 1427 respectively. The author also argues, in contrast to other scholars, that Juan did not convert to conciliarism upon his arrival in Basel, but rather that this tendency was already visible in his Salamanca days. To substantiate her argument, the author exploits the first repetitio in which Juan argued for absolute papal authority, which has conventionally been taken as implying an anti-conciliarist position. If understood in the context of struggles over the university's autonomy between members of the institution and the archbishop of Santiago, the author suggests, the repetitio is in fact a testimony to Juan's belief in collective governance.

Wolf argues that another early episode too had a lasting impact on Juan's thought. This was an encounter with a Granadan ambassador in 1431. While meetings with Muslims were not uncommon, discussions about religious matters were, and this conversation revealed to Juan the Muslim view of Christianity, which he deemed fundamentally misinformed. If only Muslims were provided with clear and accurate explanations of Christian doctrines, Juan came to believe, the power of the Christian revelation would do its work and Muslims would convert voluntarily. A third experience which shaped Juan's approach to religious disagreement was the conflict with the Hussites, from which he drew important lessons for encounters with Muslims. Instead of resorting to violence, which could be counterproductive, he believed that Christian missionaries should rely on Scripture and peaceful debate. Remarkably, unlike others who promoted dialogue, but did not object to the Crusades, Juan was opposed to military measures at a time of great fear of Muslim conquest. He held an iconoclastic view of past crusades: they had not led to sincere faith. He also pointed out a fundamental contradiction between crusading and a tradition of anti-Islamic polemics, which decried Muslims as violent. Instead, Juan emphasised the model of Christ with his mission of peace and envisaged meetings between Christian and Muslim leaders in which the latter were persuaded of the Christian truth in disputations. (He considered war as a possibility in case Muslims stubbornly refused to hear the word of God.) On the Christian side, Juan's efforts were meant to lead to more profound faith as well.

Apart from covering territory that has long needed attention, this book will be of interest to a range of readers. Those with expertise in Christian-Muslim relations will not only appreciate the attention paid to the two repetitios, but will also be impressed by Wolf's argument for Juan's consistency. Hers is also an integrated interpretation of Juan's thought, which identifies connections between his views on mission and on church reform. Outsiders to the field, including undergraduate and graduate students, will find it a clear introduction to the person and the institutions and intellectual struggles of which he was part. The author strikes a very good balance between a convincing intellectual portrait and excursions into wider contexts. What emerges is how attitudes to other religions are contingent upon circumstance, military and political constellations, individual inclination and experience, in addition to more general patterns of religious and intellectual disagreement.

Future scholarship will shed more light on Juan, notably by addressing the need to make more texts of his corpus available in edited form, as Anne Marie Wolf suggests. The book might also inspire scholars to reconsider fundamental analytical categories, such as medieval or humanist.