Venerable Pope Pius XII speaks on the nature(s) of Christ and seems to accept that both understandings can be orthodox and heterodox depending on what is meant in his encyclical, SEMPITERNUS REX CHRISTUS:
St Cyril of Alexandria, Doctor of the Incarnation, says the there is one nature but admits that there are some who teach two natures who don’t mean it to mean two persons:
For we shall not understand, as some of the more ancient heretics, that the Word of God, by having taken his own nature, that is, the divine, prepared a body for himself; but, following in every way the divinely inspired Scriptures, we strongly maintain that he took his flesh from the Holy Virgin. Wherefore, we say that the two natures were united, from which there is the one and only Son and Lord, Jesus Christ, as we accept in our thoughts; but after the union, since the distinction into two is done away with, we believe that there is one nature of the Son, as one, however, one who became man and was made flesh. But if being God the Word he is said to be incarnate and to be made man, let the suspicion of a change be cast somewhere far away, for he has remained what he was, and let the entirely unconfused union be confessed on our part. But perhaps those on the opposite side might say:
Behold, those who fashion the confession of the true faith clearly name two natures, but maintain that the expressions of those inspired by God are divided according to the difference of the two natures. Then, how are these assertions not opposite yours? For you do not allow the attributing of expressions to two persons, that is, two hupostaseis.
But, my dear friends, I would say, I have written in the propositions:
If anyone attributes to two persons, that is, to two hupostaseis, the sayings and ascribes some to a man considered separately from the Word of God, and ascribes others, as proper to God, only to the Word of God the Father, let him be condemned. - St Cyril of Alexandria, Letter 40:14
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But the brethren at Antioch, understanding in simple thoughts only those from which Christ is understood to be, have maintained a difference of natures, because, as I said, divinity and humanity are not the same in natural quality, but proclaimed one Son and Christ and Lord as being truly one; they say his person is one, and in no manner do they separate what has been united. Neither do they admit the natural division as the author of the wretched inventions was pleased to think, but they strongly maintain that only the sayings concerning the Lord are separated, not that they say that some of them separately are proper to the Son, the Word of God the Father, and others are proper to another son again, the one from a woman, but they say that some are proper to his divinity and others again are proper to his humanity. For the same one is God and man. But they say that there are others which have been made common in a certain way and, as it were, look toward both, I mean both the divinity and the humanity. - St Cyril of Alexandria, Letter 40:17
- It is indeed sad that the ancient adversaries of the council of Chalcedon (also called Monophysites) should have rejected this doctrine, so lucid, so coherent and so complete, on the strength of certain badly understood expressions of ancient writers. While they rejected the absurd teaching of Eutyches about the mixture of natures in Christ, they obstinately clung to the well-known expression: ‘One Incarnate nature of the Word God’. This expression had been used by Cyril of Alexandria (who took it from St. Athanasius) with a perfectly correct meaning, since he used the term ‘nature’ to signify ‘person’. The Fathers of Chalcedon, therefore, totally removed what was ambiguous or liable to cause error in these expressions. For they applied the same terms as are used in the theology of the Trinity, to the exposition of our Lord’s Incarnation. Thus they [Chalcedonian Fathers] made ‘nature’ and ‘essence’ (essentia, ousia) the same, and likewise ‘Person’ and ‘Hypostasis’, and they treated the latter two names as totally different in meaning, from the former two. Their [Oriental Fathers] approach, on the other hand, had made ‘nature’ the equivalent of’ Person’ not of ‘essence’ (essentia).
St Cyril of Alexandria, Doctor of the Incarnation, says the there is one nature but admits that there are some who teach two natures who don’t mean it to mean two persons:
For we shall not understand, as some of the more ancient heretics, that the Word of God, by having taken his own nature, that is, the divine, prepared a body for himself; but, following in every way the divinely inspired Scriptures, we strongly maintain that he took his flesh from the Holy Virgin. Wherefore, we say that the two natures were united, from which there is the one and only Son and Lord, Jesus Christ, as we accept in our thoughts; but after the union, since the distinction into two is done away with, we believe that there is one nature of the Son, as one, however, one who became man and was made flesh. But if being God the Word he is said to be incarnate and to be made man, let the suspicion of a change be cast somewhere far away, for he has remained what he was, and let the entirely unconfused union be confessed on our part. But perhaps those on the opposite side might say:
Behold, those who fashion the confession of the true faith clearly name two natures, but maintain that the expressions of those inspired by God are divided according to the difference of the two natures. Then, how are these assertions not opposite yours? For you do not allow the attributing of expressions to two persons, that is, two hupostaseis.
But, my dear friends, I would say, I have written in the propositions:
If anyone attributes to two persons, that is, to two hupostaseis, the sayings and ascribes some to a man considered separately from the Word of God, and ascribes others, as proper to God, only to the Word of God the Father, let him be condemned. - St Cyril of Alexandria, Letter 40:14
…]
But the brethren at Antioch, understanding in simple thoughts only those from which Christ is understood to be, have maintained a difference of natures, because, as I said, divinity and humanity are not the same in natural quality, but proclaimed one Son and Christ and Lord as being truly one; they say his person is one, and in no manner do they separate what has been united. Neither do they admit the natural division as the author of the wretched inventions was pleased to think, but they strongly maintain that only the sayings concerning the Lord are separated, not that they say that some of them separately are proper to the Son, the Word of God the Father, and others are proper to another son again, the one from a woman, but they say that some are proper to his divinity and others again are proper to his humanity. For the same one is God and man. But they say that there are others which have been made common in a certain way and, as it were, look toward both, I mean both the divinity and the humanity. - St Cyril of Alexandria, Letter 40:17