It goes without saying that “naturalism” has played an absolutely central role in art-historical discourse. This is true in two broad senses. On one hand, there is artistic practice: artists have, in various ways, relied on the observation of the visible world in the creation of images. On the other, there is the standard art-historical narrative, articulated by scholars from Pliny through Vasari to the present, which posits a diagnostic role to the perception of naturalism, gauging the degree of an image’s naturalism to discern intention and meaning, and assigns particular works to one or another art-historical epoch. Jean Givens’s new book contains a fascinating meditation on these issues. It is a significant contribution, engaging in a serious and thoughtful manner with the writings of ancient authors, more recent art-historical “classics” (such as Ernst Gombrich’s work), and current scholarship (like that of Claudia Swan and Peter Parshall). Her conclusions are worthy of the attention of all medievalists, and, more generally, of anyone concerned with the referential properties of images. Givens describes her book as rooted in three basic questions. The first and most basic of these concerns medieval artistic practice: did medieval artists rely on their observation of nature when...