The ecumenical patriarch (Οἰκουμενικός Πατριάρχης) is the archbishop of Constantinople (Istanbul) and New Rome, and primus inter pares (first among equals) among the heads of the several autocephalous churches which compose the Eastern Orthodox Church. The ecumenical patriarch is regarded as the representative and spiritual leader of the Eastern Orthodox Christians worldwide. The term ecumenical in the title is a historical reference to the Ecumene, a Greek designation for the civilised world, i.e. the Roman Empire, and it stems from Canon 28 of the Council of Chalcedon. The Ecumenical Patriarchate of Constantinople is one of the most enduring institutions in the world and has had a prominent part in world history. The ecumenical patriarchs in ancient times helped in the spread of Christianity and the resolution of various doctrinal disputes. In the Middle Ages they played a major role in the affairs of the Eastern Orthodox Church, as well as in the politics of the Orthodox world, and in spreading Christianity among the Slavs. Currently, in addition to the expansion of the Christian faith and the Eastern Orthodox doctrine, the patriarchs are involved in ecumenism and interfaith dialogue, charitable work, and the defense of Orthodox Christian traditions. Within the five apostolic sees of the Pentarchy, the ecumenical patriarch is regarded as the successor of Andrew the Apostle. The current holder of the office is Bartholomew I, the 270th bishop of that see. The ecumenical patriarch of Constantinople is first among equals, or first in honor among all Eastern Orthodox bishops, who presides in person—or through a delegate—over any council of Orthodox primates or bishops in which he takes part and serves as primary spokesman for the Orthodox communion especially in ecumenical contacts with other Christian denominations. He has no direct jurisdiction over the other patriarchs or the other autocephalous Orthodox churches, but he, alone among his fellow primates, enjoys the right of convening extraordinary synods consisting of them or their delegates to deal with ad hoc situations and has also convened well-attended pan-Orthodox synods in the last 40 years.