This is a study of the association of apocalyptic ideas with the spread of Christendom, through the processes of conquest and conversion, between the eleventh and fourteenth centuries. The terrain covered is extensive. Whalen starts with the papal reform movement, showing how its clashes with Byzantium and the western Empire were informed by apocalyptic rhetoric and programmes. He then progresses into the period of the First Crusade and the twelfth century, with balanced and well-informed analysis of the writings of such exegetes as Rupert of Deutz, Honorius Augustodunensis, Anselm of Havelberg and Gerhoh of Reichersberg. The big name of course is Joachim of Fiore, and there is no doubt that the argument moves up a gear with his appearance in chapter iv. In the following chapters Whalen affirms and illustrates the extent to which Joachim's specificity made the debates about the Last Days that were conducted during the thirteenth and fourteenth centuries more highly-charged than they had previously been. Initially the mood was optimistic. The mendicants applied themselves to the realisation of Christendom's triumph through missionary activity, while James of Vitry used prophecy to raise morale during the Fifth Crusade. But the collapse of Latin Syria in 1291, the bitter dispute within the Franciscan order over apostolic poverty and mounting criticism of the Church's failings, made it increasingly tempting to employ the discourse of apocalypticism in ways that criticised Christian shortcomings and even questioned papal authority. Unsurprisingly, the latter tendency proved dangerous for its advocates: the eschatology of Peter John Olivi, for example, was formally condemned in 1326.

There is a massive literature on medieval apocalypticism, but Whalen's focus on its association with Christendom gives his book both coherence and originality. His handling of this subject is assured and consistently interesting. He is particularly strong on the treatment of Joachim's ideas by Gerard of Borgo San Donnino, William of Saint-Amour, Aquinas and Bonaventure. Overall, though, his command of his sources rarely falters. He also writes in an engaging way and succeeds in integrating religious and political developments throughout a challengingly protracted time scale. His book deserves a wide readership and it constitutes a welcome contribution to its field.