Matt,
so I think the issue is, and was not to start a quote battle, but how is St. Leo not Cyrillian?
Maybe if Leo speaks of two natures as two essences and thus denies a compound nature/essence after the union, but Cyril speaks of a single nature after the union after the union of natures as a single hypostasis?
there has to be some specific difference, because St. Cyril distinguishes after the Union, and St. Leo upholds the Unity in the Tome.
Matt,
One of the first and key challenges is to define the term "nature" and then to see if all authors and all discussions on the unity of natures use the term "nature" in the same way.
In Flavian's Letter to Leo, he labels the two natures - "manhood" and "godhead" .
Eutyches, keeping his diseased and sickly opinion hid within him, has dared to attack our gentleness, and unblushingly and shamelessly to instil his own
blasphemy into many minds: saying that before the Incarnation indeed, our Saviour
Jesus Christ had two
natures, Godhead and manhood: but that after the union they became one nature;
http://www.newadvent.org/fathers/3604026.htm
In this context, it makes good, simple sense what Flavian meant by natures and why he objected to "one nature" compounded of two- there is no such "godheadmanhood" in Orthodoxy.
And it also seems like "natures" are synonymous with essences, substances, and categories/collections of properties (eg. divine-ness).
However, is there another potential meaning of "nature" that can justify or even encourage speaking of a whole, compound nature?
Theodoret said explicitly that "Hypostasis means nature" (as opposed to saying Nature means hypostasis). However, first, by this did he meant that hypostasis only means substance/essence/nature, or did he have in mind that a "nature" was its own entity and that hypostasis must always be used in that sense and not as substance?
Theodoret also repeatedly uses the phrase "hypostases or natures" together, but it isn't clear that hypostasis here means the same thing it does at Chalcedon where it teaches "one hypostasis".
Hypostasis etymologically means 'substance', and we also commonly equate substance with essence in Christian theology.
The Coptic argument is that "nature" to Cyril and to the Copts meant "hypostasis" in the sense of concrete reality or entity in their discussion of the union of two natures. So one of our tasks must be to see whether that definition of natures can be confirmed.
Consider Cyril's use of the word natures, where he gives examples of "body" and "soul".
Let us once more take the example of an ordinary man. We recognise two natures in him; for there is one nature of the soul and another of the body,
https://afkimel.wordpress.com/2016/01/11/st-cyril-of-alexandria-the-one-incarnate-nature-of-christ/
The body has its own nature, the soul does, and a man has his own one nature, even though it has a body and a soul, each with their own natures.
By speaking of the "
one nature of God the word incarnate", or as others translate it, the "
one incarnate nature of the Word", the point of the expression "one" seems to reflect to me the idea of a whole compound nature, otherwise the idea of "one" would be superfluous.
However, I am not sure that these kinds of quotes by Cyril shows that he meant "hypostasis"/"entity" by "nature".
When he says "the nature of the body", he does not say "the body is a nature", even though it's acceptable to say that the body is its own entity.
The Dyophysite Christology of Cyril of Alexandria By Hans van Loon reviews one author who sees hypostases and natures as sometimes synonymous for Cyril:
Jugie gives several passages, from both before and after the Council of Ephesus, in which the Alexandrian bishop uses the word physis for the humanity of Christ.... Jugie concludes that physis at times is synonymos with ousia in the sense of essence specifque, the essence of a substance....
Jugie stresses that the word did not assume human nature in general, but a concrete, individualised nature. It is a hypostasis, which signifies a reality, something existing, in opposition to pure abstractions or to appearances.... It seems that Jugie defines hypostasis here as a reality. In Contra Theodoretum Cyril writes about a coming together of hypostases or natures. Cyril rejects a union of prosopa; therefore, hypostasis cannot be synonymous with prosopon here, Jugie adds.
...
... one can say that in this formula both terms, hypostasis and physis in fact indicate a person, a separate reality. This one nature is a nature-person, a physis-prosopon.
But rather than just rely on hearsay about Cyril, it would be best to see where he defined "natures" as meaning "hypostases" in the sense of person or a separate entity.
We seem to be left with Cyril asserting two natures after the union in one sense, but
maybe not in every sense, if we accept Jugie's view. It's confusing.