This book is the text of Ulrich Horst's Robert M. Conway lecture at the Medieval Institute at the University of Notre Dame. It summarises in English his studies – in German – on the ecclesiology of some medieval and early modern Dominicans. The ecclesiological differences between early Dominicans and Franciscans were linked with views about poverty. While papal approbation of the Order of Preachers is not part of Aquinas's theological arguments, Bonaventure used papal approbation of St Francis's charism of poverty both against the claims of the secular Masters and in order to foster the unity of the Minors (cf. pp. 11–14). In 1322 Pope John xxii (who would canonise Thomas the following year) gave back to the Franciscans the ownership of their goods (passed to the Holy See in 1245). The Franciscans accused the pope of heresy because he had no right to change the ‘definitions’ of his predecessors, confirmed by a process of reception (cf. pp. 28–30). From the fourteenth century until Vitoria and Soto (sixteenth century) Dominican theologians usually insisted upon the necessary collaboration of the pope with prelates and theologians. In the same period, the Thomistic Carmelite Guido Terreni considered that the condition for the pope to teach as pope and not as private person is ‘the intention to determine a truth that concerned all of the faithful and the entire Church’ (p. 36), which neither requires nor excludes collaboration with others. Among Dominican theologians, Master-General Cajetan introduced a new element, which Horst summarises:

This summary is correct, but it might have been useful to add that Cajetan's De comparatione auctoritatis papae et concilii (1511) says how a heretical pope can be deposed, through the disjunction by a council of the papal office and its holder. In Spain, Vitoria's moderate views did not survive in a context where the Reformation was becoming a religious and political threat. For instance, in Melchior Cano's ecclesiology, the councils depended completely on papal approval (cf. p. 49). But Cano still maintained that papal decisions had to be carefully prepared. Juan de la Peña eliminates that limitation, thanks to a parallel with sacramental theology: it is enough to follow the rite according to the intention of the Church (cf. pp. 51–2). Dealing with the question of the alleged female pope Joan, Bañez turned this special problem into a general one. Should an illegitimate or dubious pope reign over the church (perhaps one who had not been baptised or whose election was somehow deficient), and should this false pope proclaim an error, it would be rendered invalid. Either the Church would never accept the error, Bañez argues, or it would be revealed at once as an error, or the pope would die before having the opportunity to render a definitive judgment. In any case there would be no negative consequences for the faith. Bañez then provided a further, and simpler, solution. If the pope were to define something de fide, it would be absolutely certain that he was the legitimate pope. Any doubt about the validity of his election would be impossible (p. 54).

If some Dominican theologians – Cano and Bañez especially – provided a theological foundation for the role of the papacy during the Counter-Reformation, the main role was then taken by Jesuits, who eliminated the necessity for the pope to prepare his decisions (reducing it to a moral obligation) and the possibility of a heretical pope: while Fr Horst gives the impression of regretting this evolution, it might actually be a logical conclusion to the Dominican theologians' will to secure the certainty of faith. Being the text of a conference, this book provides a short – but excellent – summary of its topic. The forty-two pages of endnotes demonstrate the author's extensive scholarly background and open up areas for further research.