Jean Barbeyrac was dismayed by the intrusion of theological controversy into the study of modern natural law theory. Yet the longest of the many annotations that he included in his own edition of Grotius was concerned with a theological matter. In this footnote, Barbeyrac attacked Grotius's understanding of Christian ethics as supererogatory; that is, as containing a distinction between the dictates of duty and the counsels of a higher holiness or perfection. The heart of his objection to this view was that it had pernicious psychological effects, that it fostered bigotry and immorality. He reiterated this psychological concern in his later work on the Christian Fathers. This objection to the real-world damages caused by the theory of supererogation was closely linked to his fear of skepticism and his quarrel with Bayle. Barbeyrac's rejection of supererogation also places him within an important strand of early modern thinking about the moral psychology of religion and about the ways in which religious belief could become an obstacle to moral behavior.