Chalcedonian Christianity is a term referring to Christian denominations adhering to the Definition of Chalcedon (451 AD), a religious doctrine concerning the divine and human nature of Jesus Christ. While most existing Christian denominations are considered Chalcedonian, in the 5th – 8th centuries the ascendancy of Chalcedonian Christology was not always certain.
The dogmatical disputes raised during the Council of Chalcedon led to the Chalcedonian Schism, and by consequence the formation of the non-Chalcedonian body of churches known as Oriental Orthodoxy. The so called Chalcedonian churches were the ones that remained united with the Holy See in Rome, the Ecumenical Patriarchate of Constantinople and the three Orthodox patriarchates of the East (Alexandria, Antioch and Jerusalem). Together, these five patriarchates has been considered the organizational foundation of Chalcedonian Christianity, notably from the perspective of Eastern Orthodox Church. During the reign of Emperor Justinian I they were recognised as the Pentarchy, the official leadership of the Christian Church.
Today, the great majority of Christian denominations can be considered descended from the Pentarchy, subscribing to Chalcedonian Christianity, broadly divided into the Catholic Church and the Eastern Orthodox Church (with Protestant denominations descended from the Catholic Church after the Reformation).
The groups that rejected the Chalcedonian definition were the majority of the Armenian, Coptic, and Ethiopian Christians, together with a part of the Syriac Christians. Today, these groups are known collectively as the Oriental Orthodox churches.
Some Armenian Christians (especially in the region of Cappadocia and Trebizond inside the Byzantine Empire) did accept the decisions of the Council of Chalcedon and engaged in polemics against the Armenian Apostolic Church.
Chalcedonian dogmatical dispute
The Chalcedonian understanding of how the divine and human relate in Jesus of Nazareth is that the humanity and divinity are exemplified as two natures and that the one hypostasis of the Logos perfectly subsists in these two natures. The Non-Chalcedonians hold the position of miaphysitism (sometimes called monophysitism by their opponents). Miaphysitism holds that in the one person of Jesus Christ, divinity and humanity are united in one nature, the two being united without separation, without confusion, and without alteration. This led many members of the two churches to condemn each other: the Chalcedonians condemning the Non-Chalcedonians as Eutychian Monophysites, and the Non-Chalcedonians condemning the Chalcedonians as Nestorians.
Dissent from the Chalcedonian doctrine
Those present at the Council of Chalcedon accepted Trinitarianism and the concept of hypostatic union, and rejected Arianism, Modalism, and Ebionism as heresies (which had also been rejected at the First Council of Nicaea in AD 325).
Those present at the council also rejected the Christological doctrines of the Nestorians, Eutychians, and monophysites (these doctrines had also been rejected at the First Council of Ephesus in 431). Later interpreters of the council held that Chalcedonian Christology also rejected monothelitism and monoenergism (rejected at the Third Council of Constantinople in 680). Those who did not accept the Chalcedonian Christology now call themselves non-Chalcedonian; historically, they called themselves miaphysites or Cyrillians (after St Cyril of Alexandria, whose writing On the Unity of Christ was adopted by them and taken as their standard) and were called by orthodox Christians monophysites. Those who held to the non-Chalcedonian Christologies called the doctrine of Chalcedon dyophysitism.