This book begins with a problem for twelfth-century moral thinkers. As the machinery of English government grew more powerful and more intrusive—the court of Henry II devoured both money and men—how could one find moral purpose in it? In Art and Political Thought, Laura Slater describes how men trained in the schools, the products of a Parisian education, tried to prevent English rulers from falling into tyranny. This “clerical political Augustinianism” (177) positioned royal government as the site of a spiritual struggle, where good men were obliged to wage holy warfare. It was an idea so successfully argued that kings and their courts bought into it. That battle for good government is examined over four chapters that take in English political society from Henry II to Edward III.

The innovation of this book lies in the description of where and how these political arguments took place. We are accustomed to thinking of them as textual, embedded in speculum principum literature and moral treatises. But they were as much visual as textual. Slater reintroduces us to men like Gerald of Wales and Stephen Langton as visual thinkers. Their facility with the Latin classics and the Bible was matched by their facility with visual images as a way of expressing political ideals and critiques of rulership. The premise of the book is that such images (from seals to choir screens, windows to tombs) were not simply a means of making or underlining a political point; they acted as a stimulus to debate, and stood as acts of communication in their own right.

Such a premise necessarily requires considerable attention to detail. Slater examines a series of different visual images, explaining how each served as a potent vehicle for moral argument. She is particularly interested in the development of the metaphor of “living stones” (1 Peter 2.4–9). Just as Christ had been the cornerstone of the church, the good man should cast himself as a guardian and defender of the community and the realm. Becket had been a living stone; the barons of the 1260s also aspired to such a role. The metaphor was borrowed and repurposed over the centuries; it demonstrates just how easily explicitly political arguments could be developed from the text of scripture. A glance at the index—packed with precise scriptural references—should be enough to demonstrate how seriously and thoroughly this book treats the images that could be derived from the Vulgate. Nor were the images that suffused English politics solely biblical: the gory downfall of Julian the Apostate is another recurring symbol tracked by Slater, the emperor a useful warning to tyrants.

Beyond making the case for the way text and image interacted in political argument, Art and Political Thought manages to refresh some familiar themes in medieval political thought. “Liberty” was of course the cri de coeur of thirteenth-century reformers; Slater examines how that case was made across different media—in a set of now-lost wall paintings in Canterbury cathedral, in the leaves of an Anglo-Norman verse life of Becket. She also offers a reflection on how “national” arguments were adapted by local communities with their own distinct intellectual life, most evident in a first chapter that looks at late twelfth-century Canterbury. There a visual language was worked into a developed decorative program.

Slater's fault line is the late thirteenth century, when, she argues, that concept of politics as a spiritual struggle against tyranny began to lose ground. The English crown was now in a better position to define itself; it was no longer willing to acquiesce to the principle that it was in the nature of royal power to tremble on the brink of tyranny. This was a new imaginative universe: Edward I and his grandson preferred to present royal authority as chivalrous and glorious. But even if the premise of power changed, it was still defined by its visual dimensions: fourteenth-century kingship made its arguments in miniatures and on its seals.

This is a book that repays rereading and careful attention. It includes ten color plates—their brightness and boldness only reinforcing Slater's point about the urgency and piquancy of the political messages they communicated. Readers will need to remain attentive to the individual detail of the case studies, because the political images are so dense with allusion that they require considerable unpacking. The overall product is an ambitious attempt to define what characterized English visual culture over two centuries.

On occasion, that ambition and broadness means that the complexity of the “Augustinianism” discussed here does not receive as much scrutiny as it might. The great appeal (and challenge) of the medieval Augustine was his intellectual flexibility. A vast number of moralists between 1150 and 1350 considered themselves to be avowedly Augustinian in their views; yet that label encompassed a strikingly different set of views about the nature and operation of politics. Moreover, it was not only royal government that could become the target of an “Augustinian” critique: it was ecclesiastical authority, too.

Slater's arguments raise questions about the implications of this study for the world beyond England. Even if we assume that English rulers developed an administrative system precocious by the standards of other medieval kingdoms, other kings and other polities were still advised and counseled by men of the Paris schools—men presumably just as accomplished as their English counterparts (if not more so) in arguing through visual images, and with an interest in defining their own political communities.

This book makes the case for taking medieval political ideas seriously, an exhortation that (rather sadly) still needs to be made. Slater recognizes the richness and complexity of medieval moral vocabulary—both textual and artistic. Small choices and small changes in language and imagery opened up arguments of fundamental political import. Her arguments should compel medievalists—not merely those of post-Conquest England—to go back to their own sources and think hard.