At the heart of Luís Campo Ribeiro’s monumental study lies a study of a series of manuscripts containing examples of Jesuit teaching on astrology theory and practice. They originated in lessons delivered in a mathematical class known as the Aula da Esfera (a reference to John of Sacrobosco’s textbook De sphaera) that were taught in the college of Sant Antão, the first Jesuit house in Portugal. Although these materials have been known to historians since at least the 1970s, their astrological content has remained hitherto unstudied. This neglect, Ribeiro suggests, was caused by previous generations of historians’ positivist distaste for this art, a disdain intensified by the fact that the authors of many of these works described the art they taught as ‘judicial’ astrology, a class of prediction seemingly condemned by the Church.

Jesuit astrology is structured in order to contextualise and analyse these texts. As Ribeiro observes in the concluding ‘final thoughts’, the point of departure for this book was an effort to understand how astrology could be taught in a Jesuit institution. He notes that to some, the fact that Jesuits were teaching such materials might seem incongruous given the Church’s apparent antipathy towards astrology. Addressing this point, the book opens with a discussion of astrology and its place in early modern culture, including an account of the Church’s attitudes towards astrology that focuses on the late sixteenth and early seventeenth centuries. This period witnessed the promulgation of the Tridentine Index of 1564, which included Rule ix that set out criteria for censoring works of divination including astrology. The rule installed essentially Thomist criteria to delimit the acceptable boundaries of astrology. It thus permitted forms of astrological predictions including not only those pertinent to medicine, agriculture and medicine, but also uncertain predictions pertaining to human actions. The Tridentine Index was followed in 1586 by Sixtus v’s bull Coeli et terrae, which reiterated most of the provisions of Rule ix.

Ribeiro’s survey of Catholic attitudes to astrology allows him to demonstrate that the early modern Church accepted a significant body of astrological theory and practice, thereby explaining how Jesuits could potentially reconcile their interest in this art with their faith. Although this point has previously been established by historians such as Ugo Baldini and Darrel Rutkin, Ribeiro develops it further by offering a valuable analysis of the categories ‘natural’ and ‘judicial’ astrology that have become commonplace in historiography.

Historians often use the former category to refer to licit applications of astrology, for instance in medicine, while deploying the latter to denote illicit predictions, for instance about future contingent events. Although both were contemporary terms, ‘judicial’ astrology originally referred to any form of predictive astrology, including licit prognostications about health. Over the course of the sixteenth and seventeenth century the term ‘judicial’ astrology began to be used to refer to the practice of making illicit predictions about future contingent events. This term never fully lost its original meaning, however, which explains why, for example, the Jesuit Simon Fallon could pen a treatise with the title Astrologia judicaria.

In the second section, Riberio provides a more detailed account of astrology in Jesuit culture. This involved offering summaries of the positions of an array of Jesuit authorities, including Benito Peirera, Martín Del Rio and Francisco Suárez. While Ribeiro divided them into supporters and detractors of astrology, his overviews of their position reveal a broad acceptance of the Thomist conception of the orthodox boundaries of astrology, although their precise definition of what constituted acceptable ‘natural’ astrology varied. Ribeiro also draws attention to an apparent disparity between printed and manuscript sources to suggest a degree of ambivalence in the minds of at least some Jesuits. For example, he deftly demonstrates that while Christopher Clavius – a key figure in Jesuit mathematical culture -- discussed astrology in hand-written drafts of some of his works, these materials were omitted from the printed versions. Expanding on the theme of Jesuit engagement with astrology, Ribeiro traces how members of the order used their knowledge of this art in their missions to China, Japan, India and the Americas. He shows, for example, how Jesuits with expertise in mathematics used astronomical and astrological knowledge to ingratiate themselves with the Chinese imperial court and how missionaries introduced astrological themes into their preaching. By these means, Ribeiro demonstrates that although a sophisticated understanding of astrology was restricted to a relatively small number of Jesuits, knowledge of its principles was widely diffused within the order and could be employed to serve a range of purposes.

Riberio’s study culminates in a discussion of the manuscript teaching materials produced for the Aula da Esfera. To date, Ribeiro has been able to attribute eight manuscripts discussing astrology to Jesuit authors including João Delgado, Simon Fallon, Luís Gonzaga and Francisco Costa. After providing a detailed comparison of these texts, Ribeiro offers some broader reflections on their significance. Perhaps most importantly, he notes that astrology was a standard part of Jesuit mathematical education in Portugal and, in all likelihood, in all Jesuit schools. The astrology taught in these schools also appears to have had a distinctively ‘Jesuit’ character. Most obviously, the authors went to great lengths to ensure that their teachings were in line with Catholic orthodoxy. In practice, this meant that while the Jesuits taught material derived from classic texts such as Ptolemy’s Tetrabiblos, they took efforts to prune out those aspects that were of contested orthodoxy.

One of the great strengths of Ribeiro’s study is his detailed accounts of the works of individual Jesuit theologians and mathematicians, which provide a richly detailed mosaic of Jesuit thought on astrology. Steeped in the technical details of contemporary astrology, he is an authoritative guide to the materials who can pinpoint important details. As Ribeiro demonstrates, most Jesuits framed their views within the received Thomist parameters, but his account allows the reader to appreciate the often highly nuanced differences of opinion maintained by these scholars. By tracing the ideas contained in these texts in such granular detail it is also possible to trace the various sources invoked by their authors, such as Pico Della Mirandola who penned a devastating critique of humans’ capacity to make accurate astrological predictions.

Although Ribeiro offers a detailed account of the content of Jesuit teaching on astrology, he does not engage with the institutional aspects of Jesuit pedagogy or how it was shaped by the Society’s disciplinary structures. Specifically, he does not discuss how their attitudes towards astrology were formed by their shared training within a system that mandated the study of both Aristotelianism and Thomism. As scholars such as Richard Blackwell and Jan Machielsen have shown, vows of obedience were central to Jesuit identity and the obligation to retain fidelity to the Society’s prevailing intellectual orthodoxy were taken very seriously. Such considerations matter when we are trying to understand why Jesuits adopted the attitudes that they did towards astrology. Throughout the text Ribeiro suggests that they were following an essentially Thomist approach towards astrology because this had been mandated by the centralised structures of censorship – the Inquisition and the Index of Forbidden Books – and by papal legislation. When considered from the perspective of Jesuit educational practice and internal discipline, however, it seems likely that the Jesuits discussed in Ribeiro’s book appear to be adhering to Thomist principles because to do so was consistent with the intellectual orthodoxy of their Society that was set out as early as 1543. They were, therefore, acting in agreement with the principles of censorship enunciated from the 1550s onwards rather than necessarily following them.

Jesuit astrology is an important work that makes multiple contributions to the historiography by offering a detailed and nuanced picture of the complex place occupied by operative arts in Catholic learned culture. It also offers a valuable contribution to wider scholarly efforts to account for astrology’s marginalisation from scholarly life during the seventeenth and eighteenth centuries. As Darrel Rutkin has argued, studies of curricula offer an important means to understand this process. Ribeiro’s study not only offers a valuable local case study, but also lays the foundations for the wider study of Jesuit teaching in astrology across Europe during the early modern period. His work therefore offers valuable insights into the part played by the Catholic Church in astrology’s marginalisation.