Those who insisted on the "two natures" formula were referred to as dyophysites (/daɪˈɒfəsaɪts/). It is related to the doctrine of the hypostatic union.
History
Development of dyophysite Christology was gradual; dyophysite tradition and its complex terminology were finally formulated as a result of the long Christological debates that were constant during the 4th and 5th centuries.
Dyophysitism as a position stands in opposition to the views of monophysitism, the doctrine of Jesus having one divine nature, and miaphysitism, the doctrine that Christ is both divine and human but in one nature. Dyophysites believe that the two natures are completely and perfectly united in the one person and hypostasis of Jesus Christ,[4] in union with each other and co-existing without mixture, confusion or change.[5] The importance of dyophysitism was often emphasized by prominent representatives of the Antiochene School.[6]
"If anyone shall divide between two persons or subsistences those expressions which are contained in the Evangelical and Apostolical writings, or which have been said concerning Christ by the Saints, or by himself, and shall apply some to him as to a man separate from the Word of God, and shall apply others to the only Word of God the Father, on the ground that they are fit to be applied to God: let him be anathema."
We confess that one and the same Christ, Lord, and only-begotten Son, is to be acknowledged in two natures without confusion, change, division or separation. the distinction between the natures was never abolished by their union, but rather the character proper to each of the two natures was preserved as they came together in one person (prosopon) and one hypostasis.
Nature (ousia) in the Chalcedonian sense can be understood to be referring to a set of "powers and qualities which constitute a being"[11] whereas person (prosopon) refers to "a concrete individual acting as subject in its own right."[12]
For adherents, the hypostatic union is the center of Jesus's unity (his divinity and humanity being described as natures) whereas those who rejected the Council of Chalcedon saw his nature itself as the point of unity.
Dyophisitism has also been used to describe some aspects of Nestorianism, the doctrines ascribed to Nestorius of Constantinople. It is now generally agreed that some of his ideas were not far from those that eventually emerged as orthodox, but the orthodoxy of his formulation of the doctrine of Christ is still controversial among churches.[13]
Chesnut, Roberta C. (1978). "The Two Prosopa in Nestorius' Bazaar of Heracleides". The Journal of Theological Studies. 29 (2): 392–409. doi:10.1093/jts/XXIX.2.392. JSTOR23958267.