Full Text
The Chalcedonian Definition is the council of 451's formal statement on the person of Christ. It does not replace the Nicene Creed; it interprets and guards it, ruling out both the division of Christ into two persons and the confusion of his two natures into one.
The Definition
We confess one and the same Son, our Lord Jesus Christ, the same perfect in Godhead and the same perfect in manhood, truly God and truly man… acknowledged in two natures, without confusion, without change, without division, without separation; the distinction of natures being in no way annulled by the union, but rather the property of each nature being preserved, and concurring in one Person and one Subsistence — not parted or divided into two persons, but one and the same Son.
The Four Adverbs
The heart of the Definition is its four adverbs: without confusion, without change, without division, without separation. The first two guard against blending the natures into a third thing; the last two guard against splitting Christ into two persons. Orthodox Christology, in every tradition that receives Chalcedon, lives within the fence these four words set.
The Oriental Orthodox churches did not receive the Chalcedonian Definition, holding that its 'two natures' language risked dividing Christ. They confess instead, with Cyril of Alexandria, 'one incarnate nature of God the Word,' understood as a single united nature rather than a blended one. Modern dialogue has found the two confessions far closer than the ancient division assumed. Theologos records both; the separation is described on the Oriental Orthodox tradition pages.
Historical Context
The Definition drew on two sources the council held together: the letters of Cyril of Alexandria, which guarded the unity of Christ's person, and the Tome of Leo, bishop of Rome, which guarded the distinction of his two natures. Chalcedon's achievement was to confess both at once — and the cost of that achievement was the ancient separation of the non-Chalcedonian churches.