Descartes was certain that ‘in the case of most books, once we have read a few lines and looked at a few of the diagrams, the entire message is perfectly obvious. The rest is added only to fill up the paper’ (p. 97). As several of the essays in this volume argue, in many cases in early modern Europe the diagrams, images and frontispieces seem in fact to have been as, or more, persuasive than the text itself. Each of the nine essays in this fine volume presents a detailed case study on a different aspect of the transmission of scientific knowledge. In the cases treated here, most of the transmission occurs through images and instruments, but some of the essays also demonstrate the degree to which orally transmitted information played a crucial role in the process.

Each of the essays pays close and sophisticated attention to the context of the processes of knowledge transmission, for, as Alexander Marr remarks about book publication, ‘transmission of knowledge in early modern Europe was not only scholarly; it was also rooted in skilled manual labour, governed by commerce, and orientated towards patronage and friendship’ (p. 188). In his essay on optics, Sven Dupré shows the important role that patronage, as one aspect of the context, could play. He notes that new types of visual proof emerged in Renaissance optics because ‘mathematicians appropriated a new type of knowledge (practical knowledge) and addressed a new type of audience (courtly patrons)’ (p. 38). In the optical texts he discusses, this meant that diagrams were included that, although apparently containing geometrical knowledge from the medieval perspectivist tradition, actually consisted of practical knowledge put into these older visual forms for the purposes of persuasion. Thus practical knowledge was clothed with the authority of geometry, possessing thereby a ‘connotation of proof’ (p. 37).

While all the case studies bring to light fascinating aspects of knowledge transmission, three important points emerge. First, transmission can transform content. Second, sensory knowledge, sensory investigation of the natural world, visual proof and objects of all types came to possess much more authority in early modern Europe than they had previously. Third, and above all, tangible and visible things – instruments, images and objects – have persuasive force, and became both more common and more convincing in the period between 1400 and 1700.

An example of the ways in which transmission transforms content can be found in Sachiko Kusukawa's fascinating contribution on Andreas Vesalius's anatomical and Leonhardt Fuchs's botanical illustrations. She argues that both authors used illustrations to help define the objects of their study: in Fuchs's case, that medicinal powers could be found in species as a whole, thus his illustrations are of archetypes rather than individual plants; in Vesalius's case, that his pictures were actually a part of his argument. His anatomy could be taught and disseminated only by means of images. In a similar vein, Adam Mosley makes the point that instruments demonstrating the movement of the planets were used for pedagogical purposes, to teach particular mathematical operations and to convey cosmological ideas demonstratively. Indeed Kepler even believed such an instrument could function as a true representation of the cosmos. Moreover, instruments helped princes and other patrons imagine the world, and certain imagining in turn led to the patronage of certain kinds of knowledge.

Many of the essays focus on the persuasive power of images. The ambitious contribution of Christoph Lüthy recounts how Descartes attempted to establish physics as possessing the same level of certainty as mathematics by deducing the particulars of the physical world from clear and distinct ideas. What most scholars have not realized is how copiously Descartes employed illustrations to depict his view of the physical world, often contradicting his principles in the process. According to Lüthy, Descartes maintained he was not an atomist, but who does not remember the vivid depiction of corpuscles moving in the vortices in Descartes's Principia? Descartes maintained that sense experience could only confirm rather than prove the underlying structure of the world. But his images made an appeal to sense experience in the most explicit manner an indispensable part of his argument.

Isabelle Pantin, too, focuses on persuasion by pictures in her essay examining Kepler's use of images in his Epitome astronomiae copernicanae (1617–21). He integrated images and diagrams into his text in order to describe and explain Copernican astronomy to his readers and persuade them towards it. Some of his proofs, to do for instance with the phases of Venus, are made only by means of the images and not with words. Finally, Catherine Eagleton's careful essay brings to the fore one element of knowledge transmission not often treated in the history of science: oral transmission. In her discussion of the making of portable sundials, she shows that circulation and transmission of knowledge took place by means of instruments themselves, images and texts describing them, diagrams depicting them or their geometry, and orally transmitted information about construction and use. Indeed, the oral exchange of information seems to have been a sine qua non for the instrument-makers.

This is an extremely valuable set of case studies that both illustrates and demonstrates important large-scale developments in European intellectual and visual culture. It should be read by historians of science, technology and medicine, as well as by cultural and intellectual historians.