This article aims to rehabilitate and restore the concept of heresy in the analysis of "religion" in a broad sense. Heresy is largely considered as a paradigmatically Christian, pre-modern, and, by implication, useless concept for scholarly investigations into religious phenomena today. A re-examination of the medieval concept of heresy, particularly that of William of Ockham, reveals that pertinacity as a defining feature of heresy in the medieval sense indicates heresy is the observed failure to recognize the obligatory nature, not the truth, of what authority asserts. The medieval idea of heresy may thus be redefined as the interference with the sacred, because obligations that generate the sacred are at the heart of what Emile Durkheim called "religious phenomena." The Durkheimian reconceptualization of the medieval idea of heresy serves to illuminate the mechanism of social exclusion in both religious and secular contexts.
