One of the most far-reaching consequences of the Protestant Reformation of the sixteenth century was a crisis of authority that pervaded the whole of Western Christendom. The aftermath of the Reformation saw the development of an unprecedented diversity of religious beliefs and practices in Europe, along with destabilizing wars of religion and the vigorous persecution of religious minorities. In this context the need for a criterion of religious truth became particularly acute. During the medieval period, tradition, scripture, reason, and experience had all been acceptable sources of religious authority, although they were mediated by the magisterium of the Catholic Church. Following the religious upheavals of the sixteenth century, serious challenges were issued to each of these long-established sources of authority. These challenges were underscored by new developments in the natural sciences. Copernican ideas and the revival of ancient atomism called into question long-standing scientific beliefs and prompted a reevaluation of the medieval understanding of the relationship between science and theology.