Since the first appearance of “romance” (roman) in mid-twelfth-century France, this genre of literature has been condemned by learned readers, who view it as failing to represent reality as it truly is and, in doing so, as leading its readers astray. While lengthy, narrative literary works in the vernacular at this time could treat the history of Rome or of France, it was those that addressed the history of Britain—that is, Arthurian romance—that came in for special censure. In the fictions they recounted about Merlin, it was argued, these works constituted bad science; in those about King Arthur, bad history; in those about Lancelot, bad morality; and in those about the Holy Grail, bad religion. This book argues that Arthurian romance implicitly recognizes and responds to the criticisms that were being made against it. The works of Chrétien de Troyes, the Grail Continuators, Robert de Boron, and the authors of the Vulgate and Post-Vulgate Cycles, by replaying the ongoing debates in their pages, all affirm that they are promoting good science, good history, good morality, and good religion, but in a way that asks us to reconceptualize each of these categories. If romance has always appealed to readers despite the criticisms to which it has been subject, it is because it offers a distinctive theory as to what reality is like, at odds with the dominant learned discourses of its time.