In the rich and diverse The Visualization of Knowledge in Medieval and Early Modern Europe, editors Marcia Kupfer, Adam Cohen, and J. H. Chajes take as their starting point the question of what medieval society considered worth knowing, and how it transmitted that knowledge in visual terms. More specifically, the essays in this collection investigate what Kupfer terms in her introduction the “knowledge-generating performativity of visual apparatuses” (11). This is an important distinction: the larger contribution of the nineteen essays may be to show that the medieval images and diagrams discussed do not, in fact, merely visualize knowledge. Instead of transmitting the same knowledge in a new and potentially more understandable medium or augmenting or interpreting the knowledge provided in accompanying texts using novel combinations of motifs, images and diagrams are agents or prompts for active memory construction, generating new and different knowledge in the mind of the viewer.

This more complex role is aptly framed by the volume's first essay, Mary Carruthers's “Geometries for Thinking Creatively,” which explains how medieval thinkers distinguished rote recall of memories from “rememoration”: creative reimagining or reconstitution of knowledge. Many of the essays that follow demonstrate different ways in which images became agents in this process. For instance, several essays examine the ways in which the arrangement and framing of an artwork's or diagram's parts were intended to prompt specific interpretive modes: Madeline Caviness's “Templates for Knowledge: Geometric Ordering of the Built Environment, Monumental Decoration, and the Illuminated Page,” shows how the complex geometrical frameworks into which visual narrative sequences were set relied on the contemplative practices common in the twelfth- and thirteenth-century monastic context; Faith Wallis's “Visualizing Knowledge in Medieval Calendar Science: A Twelfth-Century Family of ‘Graphic Glosses’ on Bede's De temporum ratione” also reveals framing, this time of text, with columns, arcades and grids, as “theologically evocative” (304). An image or diagram could also be a tool for action through meditation: Jeffrey Hamburger's “Mindmapping: The Diagram Paradigm in Medieval Art and Beyond,” presents several examples, both medieval and modern, of how diagrams that model the world become tools to make the desired occur, whether that was reunion of the designer with a loved one, or of the soul with God. For Lucy Freeman Sandler, “Religious Instruction and Devotional Study: The Pictorial and the Textual in Gothic Diagrams,” inserting items associated with the Passion into diagrams for contemplation converts the passive viewer of a depicted narrative into a participant in the event itself. Chajes's “The Kabbalistic Tree” sees the long parchment diagrams as both amuletic and vehicles for the ritual participation in the development of divinity.

Not surprisingly, the majority of the essays in the volume deal with material found in codices, and several use the “architecture” of the codex, as Kupfer terms it (“The Rhetoric of World Maps in Late Antiquity and the Middle Ages”), as food for thought. Two essays can usefully be read together: Lesley Smith's “Biblical Gloss and Commentary: The Scaffolding of Scripture,” argues that changes to the format of glossed texts signaled the changing ways in which they were used in pedagogy; David Stern's “The Topography of the Talmudic Page,” instead argues that the page format shaped the study that occurred, particularly as printers chose and then consolidated a textual tradition, replacing the highly mutable manuscript versions with a fixed edition that served as a uniform generator of knowledge. Ayelet Even-Ezra's “Seeing the Forest Beyond the Trees: A Preliminary Overview of a Scholastic Habit of Visualization” similarly embeds the diagrams of distinctiones she studies in their pedagogical context, and shows how the groupings reveal the analysis of their creator and work to inspire reinterpretations of the source text in those who contemplate them. A. Mark Smith's “More Than Meets the Eye: What Made the Printing Revolution Revolutionary,” by contrast describes the impatient reader of the sixteenth century plumbing the codex as an immediate reference source.

In addition to shedding new light on better known artworks and textual traditions, several of the volume's essays, notably Yuval Harari, “Functional Paratexts and the Transmission of Knowledge in Medieval and Early Modern Jewish Manuscripts of Magic,” and Linda Safran, “A Prolegomenon to Byzantine Diagrams,” cast a first and important light on understudied material.

It is clear that the field is still grappling with how to discuss the myriad visual tools and forms that artists and scribes deployed. Wallis distinguishes among grids, tables, and diagrams, assigning different functions to each: to her, “a combinatory table can become a diagram when formal or decorative modifications add a surplus of metaphysical or theological meaning” (299). Other contributors, however, use different definitions. Cohen, in “Diagramming the Diagrammatic: Twelfth-Century Europe,” equally convincingly suggests an interpretive range between text, diagram, and image based on the subject's component parts (388, 394). Sandler describes as diagrams miniatures that have motifs separated into simple gridded squares (436–40), much like Wallis's tables, but are intended as instruments. This fluidity in terminology speaks to the complexity of assessing the kinds of visual and graphic constructions that were both drawn from and added to preexisting bodies of material, and understood within varying pedagogical and cultural contexts.

Cohen also reasonably defines “image” using the dictionary definition of “a visual representation of something, such as a likeness of an object” (387–88), and yet some authors struggled to make clear when they were talking about mental figures or images rather than graphic ones (Lina Bolzoni's “Visualization of a Universal Knowledge: Images and Rhetorical Machines in Giulio Camillo's Theater of Memory” is a case in point). In some cases, it would have been helpful to have more actual images (for instance, A. Mark Smith directs us to “take a brief look” at a printed page that is not illustrated), or higher quality ones, a problem in the same article. Those complaints aside, this hefty volume is lavishly illustrated with many high-resolution color plates, and well designed. It is very welcome and should be widely read.