Abstract
John Henry Newman's theory of heresiology evolved over the course of his life, accentuating certain Christological characteristics of heresy. He began with the study of the Arian heresy, progressing through the Sabellian and Apolloniarian, and ending with the Monophysite. The theory of heresy and orthodoxy finally developed in the Development of Doctrine reflects this struggle to find common features of orthodoxy corresponding to principles governing Christology in the early Church Fathers. As a consequence, Newman's heresiology, in its final stage, holds that faith is inherently Christological, as it depends on the doctrine of the Incarnation to secure the authority of the divine voice of Christ to which one submits in faith.