This book seeks to understand what masters of theology at the University of Paris in the thirteenth century had to say about similarities and differences between humans and animals. It explores the ways in which they related similarities and differences to each other, holding them in productive tension, so as to construct a boundary between humans and animals, or to query and blur such a boundary.

Chapter 2 explores how Franciscan theologians understood the similarities and differences between animals and humans. The Summa Halensis most frequently stressed clear difference and a strong boundary. Similarities were recognized, however, especially in relation to the corporeal. The Summa was not consistent in its approach to these similarities: sometimes they were simply natural features posing no moral or intellectual challenges, whereas on other occasions they were dangerously deceptive and symbolic of human sin. Bonaventure also accepted that in many respects the bodies of humans and animals were the same. Beyond this, however, he was not struck by much in the way of similarity. He took it for granted that humans were the most perfect animals, unique amongst animals in their possession of reason. Made in the image of God, humans related to God very differently from animals. Animals served humans, answering to their bodily and even emotional needs. Bearing symbolic meaning, they were God’s tools. Bonaventure did not see any of the similarities that underpinned more complex understandings in the work of others. For Bonaventure, the boundary between humans and animals was always clear-cut.

Chapter 3 considers the work of two Dominicans, Albert the Great and Thomas Aquinas. Albert placed humans at the top of a hierarchy. He saw many similarities between animals and humans, the likeness diminishing with every step down the hierarchy. Although a hard boundary between humans and animals remained, it was just one of many that divided animals into categories, the pygmy from the human, the monkey from the pygmy, and so on. In the Summa theologiae Aquinas consistently stressed differences between humans and animals, but also noted significant similarities. Even if they could not grasp universals, for example, some animals could nevertheless think generally about types of other animal. Aquinas’s earlier work, the Summa contra gentiles, was especially imaginative in the way it explored the relationship between similarity and difference. Within the hierarchy of being, for example, he showed how difference might be generated by similarities in a variety of ways. Aquinas took an entirely different approach, however, when he set aside every aspect of the human which was in any way similar to the animal, concluding that contemplation of the truth was the sole feature that defined the human absolutely.

When Parisian theologians of the thirteenth century wrote about animals and the similarities and differences between animals and humans, there was great variety and richness in their work. While ‘the paradigm of the boundary’ persisted, ‘the plurality and density of medieval thought about animals’ that Susan Crane so brilliantly identified in vernacular literature was equally characteristic of theological texts written in Latin.1 With reference to bestiaries, Crane observed that ‘With ratio as their distinguishing feature, humans are crucially differentiated from other animals; with ratio even slightly shared out among them, animal difference is shot through with similitude’, and it is clear that for the masters ‘animal difference’ was indeed ‘shot through with similitude’.2 Moreover, while historians of philosophy like Anselm Oelze have, with immense precision and eloquence, explained the different ways in which some medieval scholars attributed various ‘rational processes’ to animals, it is also apparent that preoccupation with and desire to explore similarity between animals and humans extended into many different areas of the theologians’ endeavours, including, as we have seen, discussions of creation, the fall, divine providence, the heavens, angels and demons, virtues and passions, to list just some of the topics that prompted theologians to assess continuity between the animal and the human.

Chapter 1 demonstrates that in his De legibus William of Auvergne emphasised the differences between animals and humans, regarding them chiefly as tools. God used them to shape human behaviour, both by demanding sacrifice and by granting them symbolic meaning. Demons used them in natural magic. Humans used them as valuable and sometimes necessary property in pursuit of survival, and to ensure proper relations with God. In the De universo, however, William noted significant similarities between animals and humans. Some animals knew and thought in very similar ways to humans. The power of their wills was similar to that of humans. These similarities were most likely to receive attention when William discussed providence or when he analysed animals in order to work out the nature of higher beings on the grounds that if something of lower standing in the hierarchy of being had a power or quality, beings higher up must also possess that same power or quality, though to a greater degree and perhaps with other powers in addition. This last approach meant that William treated animals as a profoundly valuable learning resource, one predicated on the existence of meaningful similarities across the boundaries that structured the hierarchy.

Henri Bouillard introduced us to the idea that, while in Italy, Thomas Aquinas, likely with access to the Papal Court’s library, encountered Augustine’s two later anti-Pelagian works De Praedestinatione Sanctorum and De Dono Perseverantiae. All evidence indicates that these tracts influenced Aquinas’s account of grace. Bouillard’s research is groundbreaking, but not complete. Having confined himself to the topics of grace and conversion, Bouillard does not expound on a second insight Thomas gleaned from Augustine in those works. Further evidence shows that Aquinas’s Augustinian discovery altered how he thought about the human agent’s ability to merit the grace of perseverance. This has ramifications for how Thomas understands one’s ability to continue in a life of virtue simpliciter.

Throughout our study, we have remained close to the texts of Aquinas and emphasized accepting those texts as a whole. The treatise on good habits (i.e., virtue and gifts) must be read in light of the treatise on bad habits (i.e., sin and vice). This latter treatise, again, must be read in the light of the treatise on grace. To approach our investigation with our own modern criteria of the kind of texts and arguments we would accept from Aquinas would do nothing but reveal what we implicitly expected to find. Despite the attention we have given to these texts, until now we have failed to discuss Thomas’s most obvious declaration on virtue, his formalized definition of it. In closing our examination, then, we turn finally to this formal definition not as a point of departure but as a point of arrival. It acts as a confirmation of what we have now worked out.

The themes of grace and nature were in a phase of development even in the years preceding Thomas Aquinas. This was, in part, due to the innovations within and between speculative frameworks involving the categories of both nature and the supernatural. These developments both were Aquinas’s inheritance and would become the subject of his own innovations. Scholars of Aquinas’s writings throughout the centuries, including Bouillard, Lonergan, and Wawrykow, have gestured toward systematic developments in Aquinas’s theology of grace. While each of these voices has made use of Thomas’s transformations for his own purpose, I have found no study throughout this history that traces the impacts of these shifts on Aquinas’s account of virtue. This is a major aspect of our challenge. Both the dynamic situation occurring in the mid-thirteenth century, combined with Aquinas’s own textual discoveries in the early 1260s, moved his theology of grace in such a manner that one can worthily examine his account of God’s grace for clues to how he understood virtue to act in our moral lives.

At the beginning of our survey regarding the conditions for virtue, we called attention to the various gradations in virtue.* While the taxonomy made it possible for our disquisition to presuppose what Aquinas had in mind when he speaks of virtue simpliciter, we stopped short of identifying that form of virtue secundum quid most advantageous for us to explore. Unsurprisingly, within our schema, there can be only one notion of virtue simpliciter. However, as noted, Aquinas’s readers have distilled at least four other gradations of virtue. In one way or another, each of these inferior gradations takes the nomination of “virtue,” but certainly not in the full sense of the term.