ABSTRACT Reformed Christianity's qualified embrace of freedom of conscience is perhaps best represented by William Ames (1576–1633). This essay explores Ames's interpretation of conscience, his understanding of its relationship to natural law, Scripture, and civil authority, and his vacillation on the subject of conscientious freedom. By rooting his interpretation of conscience in natural law, Ames provided a foundation for conscience as an authority whose convictions are binding and worthy of some civil respect and freedom. At the same time, his Puritan worldview ultimately required the deference of conscience to the superior manifestations of divine law in Scripture and civil institutions. As a result, Ames provided raw ingredients for a theological doctrine of freedom of conscience despite his unwillingness to commend the idea himself consistently. In this way, Ames symbolizes an ambiguity on freedom of conscience characteristic of the broader Reformed tradition.