Is there only one nature in Jesus Christ?
The Fourth Ecumenical Council (Chalcedon, 451; see Q070) clarified the theology and the language to be used:
Following the holy fathers, we all with one voice teach the confession of one and the same Son, our Lord Jesus Christ: the same perfect in divinity and perfect in humanity… of a rational soul and a body; consubstantial with the Father as regards his divinity, and the same consubstantial with us as regards his humanity, like us in all respects except for sin… acknowledged in two natures which undergo no confusion, no change, no division, no separation; at no point was the difference between the natures taken away through the union, but rather the property of both natures is preserved and comes together into a single person and a single hypostasis; he is not parted or divided into two persons, but is one and the same Only-Begotten Son, God, Word, Lord Jesus Christ. (Definition of the Council of Chalcedon, 451)
For complex historical and terminological reasons, this confession was not accepted by some within a sizable family of ancient Churches, in Egypt, Ethiopia, Eritrea, Armenia, Syria, and India, commonly called the Oriental Orthodox or non-Chalcedonian Churches (and, less accurately, “monophysite”). An official theological dialogue has been conducted with these Churches, whose agreed statements (Anba Bishoy, 1989; Chambésy, 1990) express the conviction that, properly understood, the dogmatic teaching of the Fourth Council and the Christology of St Cyril of Alexandria confess the same faith of the Scriptures and the early Fathers, though full communion has not been restored.
As the Council confessed, Jesus Christ is one divine person, the Word of God who became flesh (Joh 1:14; see Q139, Q150). The natures are two; the Son is one. It is therefore one and the same who works wonders as God and suffers as man; and for this reason, the Church rightly says that God was born of the Virgin, and that the Lord of Glory was crucified (1Co 2:8; see Q167). This truth is beautifully expressed by St Leo the Great, Pope of Rome, in his revered Tome:
For each form [nature] does the acts which belong to it, in communion with the other: the Word, namely, performing what belongs to the Word, and the flesh carrying out what belongs to the flesh. One of these shines with miracles, the other succumbs to injuries… It is one and the same person who is truly the Son of God and truly the Son of Man. Tome of Leo (Letter 28 to Flavian)
The grammar of this definition bears beyond Christology. Chalcedon confesses that in Christ what he is (nature) and who he is (person) are not the same, and that the one person of the Son is the subject of both natures. Because our nature exists in him personally, and because his person is not bounded by the necessity that governs created nature, human nature in Christ is set free from what held it. St Maximus the Confessor expresses this by distinguishing the principle of nature (logos physeos), which is not altered, from the mode of its existence (tropos hyparxeos), which is made new (Ambigua 42). What is given to us in the Holy Mysteries is precisely this new mode of existence (see the Study on Person, Nature, and Communion).
