Papal primacy, also known as the primacy of the Bishop of Rome, is an ecclesiastical doctrine concerning the respect and authority that is due to the pope from other bishops and their sees. English academic and Roman Catholic priest, Aidan Nichols, wrote that "at root, only one issue of substance divides the Orthodox and the Catholic Churches, and that is the issue of the primacy." Other Orthodox Christian theologians, however, view primacy as authoritative power: the expression, manifestation and realization in one bishop of the power of all the bishops and of the unity of the Church.