The Council of Chalcedon is important in the history of Christianity, because it helped harmonize Saint Cyril of Alexandria’s Christology with the historical Christology of the West. These Christologies were identical during their day. The actual decree of Chalcedon that delineates the council’s Christology specifically quotes and parallels Cyril’s Christology and at one point, even his deposed successor: Dioscorus. When read passage by passage, one is left with no doubt that the decree of Chalcedon is an authentically Cyrillian document.

As follows is the definition of Chalcedon in italics, with citations to Cyril afterwards. The following was compiled by an anonymous seminary graduate.

Following the holy Fathers we teach with one voice that the Son and our Lord Jesus Christ is to be confessed as one and the same…

 “We continue to hold that this unity is wholly unbreakable, since we believe that the Only-Begotten and the firstborn are the same individual, the Only-Begotten insofar as he is the Word of God the Father who appeared from his very essence, and first-born insofar as he became man and was one ‘among many brothers.’”  (To Theodosius, vol. 129 of The Fathers of the Church, [Washington, D.C: The Catholic University of America Press, 2014], p. 51).

…that he is perfect in Godhead and perfect in manhood, very God and very man…

“…he is God and man and just as he is perfect in divinity so also is he in his humanity…” (St. Cyril of Alexandria, Epistle 44, vol. 76 of The Fathers of the Church, trans. John I. McEnerney, 201-202)

… of a reasonable soul…

“Therefore, if anyone says that the word was made flesh, he confesses that the flesh which was united to him was not without a rational soul.” (Epistle 46, vol. 76 of The Fathers of the Church, trans. John I. McEnerney [Washington, D.C: The Catholic University of America Press, 1987], p. 199)

… and body consisting, consubstantial with the Father as touching his Godhead, and consubstantial with us as touching his manhood…

“The same one is consubstantial with the Father according to the Godhead, and consubstantial with us according to the manhood…” (Statement affirmed by Cyril from John of Antioch, Formula of Reunion, Cyril’s Letter to John of Antioch, trans. John McGuckin, from St. Cyril of Alexandria and the Christological Controversy, [Crestwood, NY: St. Vladimir’s Seminary Press, 2004], p. 344)

…made in all things like unto us, sin only excepted…

“The word became flesh, but not sinful flesh, rather ‘in the likeness of sinful flesh.’ He lived as a man with earthly beings, and came in our likeness, but he was not subject to sin like us, but was far beyond the knowledge of any transgression.” (On the Unity of Christ, trans. John McGuckin, [Crestwood, NY: St. Vladimir’s Seminary Press], p. 89).

…begotten of his Father before the worlds according to his Godhead; but in these last days for us men and for our salvation born of the Virgin Mary, the Mother of God according to his manhood.

“[W]e were taught according to the divine Scripture and the holy Fathers and we confess that one Son and Christ and Lord, that is, the Word of God the Father, was begotten of him before ages in a divinely fitting and ineffable manner and that in recent ages of time the same Son was begotten for us according to the flesh from the Holy Virgin, and since she gave birth to God made man and made flesh, for this reason we also call her the mother of God.” (Epistle 45, vol. 76 of The Fathers of the Church, trans. John I. McEnerney [Washington, D.C: The Catholic University of America Press, 1987], p. 191).

This one and the same Jesus Christ, the only-begotten Son must be confessed to be in two natures…

“Therefore, as far as concerns our understanding and only the contemplation by the eyes of the soul in what manner the only begotten became man, we say that there are two natures which are united, but that Christ the Son and Lord is one, the Word of God the Father made man and incarnate.” (Epistle 45, vol. 76 of The Fathers of the Church, trans. John I. McEnerney [Washington, D.C: The Catholic University of America Press, 1987], p. 193).

“…the only–begotten Son of God in so far as he is known to be and is God did not endure the sufferings of the body in his own [divine] nature but suffered rather in his earthly nature.” (St. Cyril of Alexandria, Epistle 44, vol. 76 of The Fathers of the Church, trans. John I. McEnerney, 201-202)

“…at the level of nature, the flesh is something quite different from the Word that was begotten of God the Father. In fact it would be perfectly reasonable to think so, and could not be gainsaid. And of course the Only-Begotten is, in turn, something different at the level of his own nature. But to acknowledge this is not the same as separating the natures after they have been united….Even though, however, the body and the Word of God the Father belong to different natures, there is only a single Christ and Son, God and Lord, despite his becoming flesh.” (Against Bishops of Oriens, from St. Cyril of Alexandria: Three Christological Treatises, trans. Daniel King, vol. 129 of The Fathers of The Church, [Washington D.C.: The Catholic University of America Press. 2014,] P. 142)

…unconfusedly, immutably, indivisibly, inseparably…

“‘We speak of neither confusion nor division nor change. Anathema to whoever speaks of confusion or change or mixture.’” (Dioscorus of Alexandria quoted in Price and Gaddis, Chalcedon, Vol 1., p. 185)

“[W]e assert the union of the Word of God the Father to his holy body which has a rational soul, a union which is ineffable and beyond thought and which took place without blending, without change, without alteration…Considering, therefore, as I said, the manner of his Incarnation we see that his two natures came together with each other in an indissoluble union, without blending and without change, for his flesh is flesh and not divinity.” (Epistle 45, vol. 76 of The Fathers of the Church, trans. John I. McEnerney [Washington, D.C: The Catholic University of America Press, 1987], p. 192-193)

…but rather the peculiar property…

“The nature of the Word has not passed over into the nature of the flesh. Neither has the nature of the flesh passed over into the nature of the Word, but remaining and being considered in the property according to the nature of each ineffably and inexplicably united…” (Epistle 46, vol. 76 of The Fathers of the Church, trans. John I. McEnerney [Washington, D.C: The Catholic University of America Press, 1987], p. 201).

… of each nature being preserved and being united in one Person (πρόσωπον)…

“…we understand him to be in one prosopon, for there is One Lord Jesus Christ, even though we do indeed take cognizance of the difference of natures out of which we may say the ineffable union was formed.” (Cyril’s Letter to John of Antioch, trans. John McGuckin, from St. Cyril of Alexandria and the Christological Controversy, [Crestwood, NY: St. Vladimir’s Seminary Press, 2004], p. 344)

…and subsistence (ὑπόστασιν),…

“If anyone does not confess that the word of God the Father was hypostatically united to the flesh so as to be One Christ with his own flesh, that is the same one at once God and man, let him be anathema” (The Third Letter of Cyril to Nestorius, trans. John McGuckin, from St. Cyril of Alexandria and the Christological Controversy, [Crestwood, NY: St. Vladimir’s Seminary Press, 2004], p. 273).

…not separated or divided into two persons…

“Those who divide him into two prosopa inevitably conceive of him as two sons. A human being like ourselves cannot properly be divided into two prosopa, even though he is regarded as consisting of a soul and a body, but in a single human being with a single identity.” (St. Cyril of Alexandria, An Explanation of the Twelve Chapters as found in Cyril of Alexandria, trans. Norman Russell, (New York, NY: Routledge, 2000), p. 182).

“…the Word himself, was genuinely united to a human nature, quite apart from any change or confusion…” (Against Theodoret, vol. 129 of The Fathers of the Church, [Washington, D.C: The Catholic University of America Press, 2014], p. 93)

…but one and the same…

“[W]e confess one Christ, Son and Lord, the Word of God the Father, the same God and man, not one and another, but one and the same, being, and known to be God and man” (Epistle 45, vol. 76 of The Fathers of the Church, trans. John I. McEnerney [Washington, D.C: The Catholic University of America Press, 1987], p. 192).

… Son and only-begotten, God the Word, our Lord Jesus Christ, as the Prophets of old time have spoken concerning him, and as the Lord Jesus Christ hath taught us, and as the Creed of the Fathers hath delivered to us.

The preceding is original to Chalcedon.

Conclusion. Any basic reading of Chalcedon’s decree reveals it is not quoting Theodoret, Saint Leo of Rome, or anyone suspect to present day Non-Chalcedonians. Ironically, the document somewhat torturously quotes Cyril and at one point, even Dioscorus of Alexandria! It should be no surprise that the decree itself was penned mostly by Dioscorus own partisans from Ephesus 2. According to Price and Gaddis:

Apart from Anatolius and the Roman delegates, no fewer than 13 of the remaining 18 had supported Dioscorus at Ephesus II, for which offence three of them (Juvenal of Jerusalem, Thalassius of Caesarea in Cappadocia, and Eusebius of Ancyra) had been suspended at the end of the first session [of Chalcedon]. The only bishop from Syria was Maximus of Antioch, a belligerent supporter of Cyrillian theology, consecrated bishop by Anatolius while the latter was still supporting Dioscorus. The list contains no known allies of Theodoret,… (Price and Gaddis, Chalcedon, Volume 2, p. 188-189).

Hence, to read the decree of Chalcedon as intending to convey the theology of Nestorius and not Cyril, when it was written by Cyrillians and it quotes/conceptually parallels Cyril’s own writings repeatedly, is simply a slander. On what basis then, one must ask oneself, is there a Non-Chalcedonian movement today? It cannot be over any alleged abandonment of Cyril’s Christology. This, simply, had not occurred.