 Soon Ockham began to write about the conflict between John and the Roman Empire, and, like Marsilius, he saw the papal claim to fullness of power as the root of many  evils.[68]  Unlike Marsilius, however, he did not reject the idea of papal fullness of power in every sense. Against Marsilius (whom he quotes extensively on this  topic),[69]  Ockham defended the traditional belief that Christ appointed Peter as head of the Church, and he held that the pope, as Peter’s successor, has supreme power in the Church. The pope and other clergy must not become involved in secular affairs, regularly, but in exceptional circumstances, Ockham says, when no lay person is able or willing to take the lead in some matter necessary to the welfare of the Christian community, the pope may intervene in secular matters. This is an application of Aristotle’s notion of epieikeia (see  §7).  The pope’s regular power in religious matters and occasional power to intervene in secular matters justify the traditional ascription to the pope of fullness of power. However, this fullness of power is not omnipotence. Not only must the pope respect the moral law and the teachings of the Church, but he must also respect rights based on human law and compact, and he must respect the Gospel liberty of  Christians.[70]  A pope who oversteps these bounds may be deposed; indeed, if his action involves heresy, he is deposed ipso facto—and according to Ockham, Popes John XXII and Benedict XII were  heretics.[71] 