<P> Its most important achievement was to issue the Chalcedonian Definition, stating that Jesus is "perfect both in deity and in humanness; this selfsame one is also actually God and actually man ." The Council's judgments and definitions regarding the divine marked a significant turning point in the Christological debates . </P> <P> Chalcedon was a city in Bithynia, on the Asian side of the Bosphorus; today the city it is part of the Republic of Turkey and is known as Kadıköy (a district of Istanbul). </P> <P> The Council of Chalcedon was convened by Emperor Marcian, with the reluctant approval of Pope Leo the Great, to set aside the 449 Second Council of Ephesus which would become known as the "Latrocinium" or "Robber Council". The Council of Chalcedon issued the Chalcedonian Definition, which repudiated the notion of a single nature in Christ, and declared that he has two natures in one person and hypostasis . It also insisted on the completeness of his two natures: Godhead and manhood . The council also issued 27 disciplinary canons governing church administration and authority . In a further decree, later known as canon 28, the bishops declared that the See of Constantinople (New Rome) had the same patriarchal status as the See of Rome . </P> <P> The teachings of the Council are accepted by the Eastern Orthodox Church, the Catholic Church (collectively known as the Great Church), Old Catholics and various other Western Christian groups . As such, it is recognized as infallible in its dogmatic definitions by the Catholic and Eastern Orthodox Churches . Most Protestants also agree that the teachings regarding the Trinity and the Incarnation, as defined at Nicaea (in 325) and Chalcedon, are orthodox doctrine to which they adhere . The Council, however, is not accepted by the Oriental Orthodox churches . These include the Coptic Orthodox Church of Alexandria, Ethiopian Orthodox Tewahedo Church, Eritrean Orthodox Tewahedo Church, Syriac Orthodox Church, Malankara Orthodox Syrian Church, and the Armenian Apostolic Church . They instead teach that "The Lord Jesus Christ is God the Incarnate Word . He possesses the perfect Godhead and the perfect manhood . His fully divine nature is united with His fully human nature yet without mixing, blending or alteration" These Churches claim that this latter teaching has been misunderstood as monophysitism - an appellation with which they strongly disagree . Nevertheless, the Oriental Orthodox churches refuse to accept the decrees of the Council . </P>

Why did the council of chalcedon take place