Irenaeus asserted the Doctrine of Apostolic Succession to counter the claims of heretics, especially the Gnostics who were attacking the theology and authority of the mainstream Church. He stated that one could find true teaching in several leading episcopal sees, not just at Rome. The doctrine he asserted, therefore, has two parts: lineage from the Apostles and right teaching. Even today a bishop can be in the line of succession, but schismatic and heretical as is the case with many episcopi vagantes who claim to or may have Catholic Orders, but have no following and have deviated from the Catholic orthodox faith as defined by the larger denominations such as the Orthodox, Anglicans, Catholics and Lutherans.