Between 1100 and 1600, the emphasis on reason in the learning and intellectual life of Western Europe became more pervasive and widespread than ever before in the history of human civilization. Of crucial significance was the invention of the university around 1200, within which reason was institutionalized and where it became a deeply embedded, permanent feature of Western thought and culture. It is therefore appropriate to speak of an Age of Reason in the Middle Ages, and to view it as a forerunner and herald of the Age of Reason that was to come in the seventeenth century. The object of this study is twofold: to describe how reason was manifested in the curriculum of medieval universities, especially in the subjects of logic, natural philosophy and theology; and to explain how the Middle Ages acquired an undeserved reputation as an age of superstition, barbarism, and unreason.