This somewhat inelegant book, dense with detail, swollen by redundant repetition, and marred by the inexplicable lack of an index, is none the less an important one and makes a substantial contribution to our understanding of the great struggle between Eugenius iv and the Council of Basle. That struggle pivoted, ideologically speaking, on the great question concerning the final locus of authority in the universal Church. And it is Decaluwe's contention that historical research on Basle has focused too exclusively on conciliarists and council and too little on pope and papal policy. This imbalance he sets out to rectify and does so with considerable success. He emphasises that the course of events at Basle was determined by the shifting relationships among three groups: the wholly outnumbered group of outright papalists, the majority group of ‘power-centralising’ conciliarists seeking to concentrate ecclesiastical authority in the hands of the general council, and the mediating minority, headed by Cardinal Cesarini, committed to a ‘power-sharing’ form of conciliarism and content to see authority shared between pope and council. By the 1440s the ‘power-centralising’ conciliarists had secured complete control over the council, thereby nudging into the papal camp many of the minority (leaders like Cesarini and Nicholas of Cusa included) and preparing the ground for the ultimate papal victory over the council. But the defeat involved was a defeat not only for Basle but for the papacy as well, forced as it was to cede to the temporal sovereigns whose support it needed much of its real spiritual power over the national Churches and to recast itself as an essentially temporal monarchy akin to others. Basle may have been brought to an end but the conciliar ideology had not been erased, and the locus of supreme authority in the Church was to remain for centuries a neuralgic quaestio disputata. Decaluwe rightly makes much of the role played in all of this by the extended interpretation given at Basle to the Constance superiority decree Haec sancta (1415). Unfortunately, he is not altogether clear about the precise nature of the extension involved. If all he means is that Basle took the decree to ascribe to the council an overall superiority over the pope extending beyond the three issues specified by Constance (papal heresy, schism and reform), then he would appear to be correct. But he seems also to suggest that the conciliar superiority asserted by Constance was intended to apply only to an emergency situation in which there was no legitimate pope but only disputed claimants to the papal office. And here he is surely wrong. As Gerson pointed out to Martin v in 1418, when Constance, relying on the provisions of Haec sancta, had moved to depose John xxiii, it believed itself to be deposing no mere ‘claimant’ but rather the ‘verus papa’. And the highly specific phrasing of contemporary conciliar and curial documents makes it clear that in holding that view Gerson was not exceptional.