The definition defines that Christ is "acknowledged in two natures", which "come together into one person and one hypostasis". The formal definition of "two natures" in Christ was understood by the critics of the council at the time, and is understood by many historians and theologians today, to side with western and Antiochene Christology and to diverge from the teaching of Cyril of Alexandria, who always stressed that Christ is "one". However, a modern analysis of the sources of the creed (by A. de Halleux, in Revue Theologique de Louvain 7, 1976) and a reading of the acts, or proceedings, of the council (recently translated into English) show that the bishops considered Cyril the great authority and that even the language of "two natures" derives from him.
Regarding the Person of Christ and the Hypostatic union, Chalcedonian Creed affirmed the notion that Christ is "One Person", having "One Hypostasis". The christological notions of "One Person" (monoprosopic - having one prosopon / Greek term for person) and "One Hypostasis" (monohypostatic - having one hypostasis) were stated explicitly, in order to emphasize Council's anti-Nestorian positions.
The Chalcedonian Definition was written amid controversy between the Western and Eastern churches over the meaning of the Incarnation (see Christology), the ecclesiastical influence of the emperor, and the supremacy of the Bishop of Rome. The Western church readily accepted the creed, but some Eastern churches did not.
It became standard orthodox doctrine. However the Coptic Church of Alexandria dissented, holding to Cyril of Alexandria's preferred formula for the oneness of Christ's nature in the incarnation of God the Word as "out of two natures". Cyril's language is not consistent and he may have countenanced the view that it is possible to contemplate in theory two natures after the incarnation, but the Church of Alexandria felt that the Definition should have stated that Christ be acknowledged "out of two natures" rather than "in two natures".
This miaphysite position, historically characterised by Chalcedonian followers as "monophysitism" though this is denied by the dissenters, formed the basis for the distinction from other churches of the Coptic Church of Egypt and Ethiopia and the "Jacobite" churches of Syria, and the Armenian Apostolic Church (see Oriental Orthodoxy).