In their attempts to explain the origins of the great European witch craze, historians have long been troubled by one problem in particular: how to supply a link between witchcraft as attested in early medieval folklore and the apparently sudden and unprecedented emergence, at some point after 1400, of a belief in the existence of an organised conspiracy of witches secretly in league with the devil. In particular, whence came the belief that witches entered into a satanic pact, formally pledging themselves to maleficium on behalf of Satan as their master, and hence to a terrifying and widespread plot to undermine the very foundations of Christian society? Although much work has been done on the psychological and social foundations for such beliefs, most notably by Carlo Ginzburg, Norman Cohn and Richard Kieckhefer, it has generally been assumed that the idea of a satanic pact was not fully developed in high theological discourse until the very eve of the Protestant Reformation. Alain Boureau's thesis challenges such assumptions by drawing attention to the extraordinary consultations amongst theologians commissioned by Pope John xxii in the 1320s, in which the idea of a satanic pact was explicitly mentioned and from which emerged the bull Super illius specula condemning any converse with demons as tantamount to heresy and hence, potentially, as a matter for inquisitorial suppression. Little of Boureau's evidence is new. Super illius specula, despite continuing doubts as to its authenticity (by no means entirely laid to rest by Boureau), has long been one of the canonical texts in the history of witchcraft. The theological debate commissioned by John xxii was rediscovered in the 1950s, although Boureau himself has recently supplied it with a definitive edition and commentary (Le Pape et les sorciers, Rome 2004). What is new here is Boureau's willingness to engage with various of the more avant-garde fringes of scholastic theology, and in particular with Aquinas's De malo and the critique of Aquinas by Peter Olivi and his followers. Exploiting his mastery of the scholastic sources, Boureau suggests that, by the 1320s, a revived concern with demons, fears for the institutional order of a Church threatened by heresy and by antinomian claims to spiritual revelation unmediated by correct ecclesiastical authority, newly refined ideas of the human body as a vessel open to invasion or occupation by spiritual agencies, and a new contractual approach to the relations between God and man mediated via the eucharist, may not only have encouraged belief in the possibility of a contract between man and the forces of evil, but had already begun to merge into a powerful, if for the most part unarticulated, assumption that demonic pacts were possible, perhaps widespread and in all events greatly to be feared. Coming in the wake of Nancy Caciola's superbly illuminating enquiry into medieval approaches to spiritual possession (Discerning spirits, Ithaca, NY 2003, cited although appearing too late to be properly exploited here), and in many ways complementing the approach to Johannes Nider and the fifteenth-century witchcraft manuals adopted by Michael Bailey (Battling demons, University Park, Pa 2003, not cited here), Boureau's exploration of scholastic approaches to demonology has many important insights to offer. All the more pity, therefore, that many readers will find his book very difficult and often very frustrating. Partly this is due to method. Trained initially as a philosopher, Boureau has long shown himself to be both a prolific and an extremely subtle writer: so subtle indeed that one wishes on occasion that he would nail his rhetorical colours more firmly to the mast of unambiguous statement. Like much of his work, the book under review uses historical sources not so much for their own sake but as a means of access to mentalités and hence to that fissile ground where ideas first develop, in many cases long before such developments are expressed through any practical consequence. Boureau's speculations are often fascinating and, for those who can follow them, delightfully provocative. He makes mincemeat, for example, of that three-legged sacred cow of modernism ‘the other’, and no one is better equipped than Boureau to point out the ways in which Aquinas, far from supplying a standard measure for orthodoxy, was very frequently either far too conservative or far too radical for his contemporaries' taste. On occasion, however, the ideas of various of Boureau's medieval authorities – Olivi, Scotus and even Aquinas – are expounded more as if they were groping towards the ontology of Sartre's L'Être et le néant than as the thoughts of those living in a pre-Cartesian world of popes, demons and pastoral theology. For a scholar trained in philosophy, it is particularly frustrating that Boureau is so uninterested in the links between thought and philology. He devotes an entire, and extremely densely argued chapter to expounding ideas on contract, for example, without properly distinguishing the various and significantly different words used to define such contracts: a pact, it should be noted, is not necessarily the same as a ‘liga’, a ‘confederatio’, a ‘syndicatus’ or a ‘conventio’, let alone as a ‘pactum’. This insensitivity to words carries us on to the second chief problem with this book: the English translation. It is not an easy task to follow Boureau's verbal acrobatics, even in French, and the translator here appears on occasion to have abandoned all but a semblance of reproducing Boureau's swoops and dives upon the intellectual trapeze. There are too many Gallicisms rendered directly into English (‘to expulse’ for ‘to expel’, ‘cultual’ for ‘cultic’, ‘a great verbal exaltation’ for something altogether less tautological), too many obscure or technical terms left unexplained (‘hylemorphism’, ‘didascaly’ and, with shades more of the Jabberwock than of standard English, ‘caliginous’), a great welter of split infinitives, and rather too many proper names supplied in French or Francophone forms (‘Peter of John Olivi’, ‘Clunisien’ for ‘Cluniac’, ‘Gervais’ for ‘Gervase’ of Tilbury', ‘Sainte-Croix’ when the church in question is an Italian ‘Santa Croce’, and so one might go on). All of this is regrettable, not least because this is a book that penetrates far deeper beneath the surface of medieval thought than most historians of witchcraft have been prepared to venture, and one which, for all of its philosophical armour-plating, is blissfully free of either post-modernist claptrap or empty posturing. Boureau has not, I think, proved that the idea of a pact between man and Satan commanded widespread belief before the fifteenth century: on the contrary, his one authority to refer explicitly to such a possibility, Enrico del Carretto, writing for John xxii in the 1320s, just as explicitly veers away from it. In his search for such an idea, he has, none the less, excavated all manner of interesting speculations and rummaged through any number of previously underexploited sources. For those wishing to understand the origins of the European witch craze, I would recommend an entrée of Norman Cohn followed by a main course of Nancy Caciola. Boureau, as befits one of the giants of modern French historical method, should be taken as a complex but none the less invigorating liqueur, once the more solid matter has been properly digested.