As for his theology, its leading factors were - (i.) the teachings of the apologists; (ii.) the philosophy of the Stoics; (iii.) the rule of faith, interpreted in an anti-Gnostic sense, as he had received it from the Church of Rome; (iv.) the Soteriological theology of Melito and Irenaeus; (v.) the substance of the utterances of the Montanist prophets (in the closing decades of his life).