Dear brother Adrian,
Thank you for the question. I perceive two points for discussion here (brother Adrian, any explanation I give below is not intended to presume that you do not already know, but only for the benefit of readers who may not know):
1) The issue between “in two natures” and “from two natures.”
The diophysite teaching uses the phrase “in two natures,” while the miaphysite teaching uses the phrase “from two natures” to describe the Person or Hypostasis of Christ. Diophysites and miaphysites both accept that Christ is “from two Natures.” The apparent historical disagreement came when considering what happens after (or upon) the hypostatic union of two natures:
- Diophysites teach that Christ still has two distinct Natures, united per the Four Adverbs (see below);
- Miaphysites teach that Christ has one Nature that is both human and divine, also united per the Four Adverbs.
What complicated matters was the language (as usual). The terms at issue were hypostasis, ousia (Latin, natura), physis, and prosopon. I don’t have time to explain them right now and how it relates to the issue of one/ two natures. If anyone is interested, let me know, or perhaps someone else can do so. In any case, this difference in language is the main reason why extremists within EO’xy have blocked official, synodal acceptance of the agreements formulated by several OO-EO commissions on the matter, while the OO and CC are already formally united on the matter.
2) Whether a miaphysite Catholic is going against the infallible Magisterium of the Church (or, alternatively, “Is a miaphysite Catholic an oxymoron?”).
The touchstone of the unity in Faith between diophysites and miaphysites is known – innocuously enough - as “the Four Adverbs”: without confusion (or mixture); without alteration (or mingling); without division; without any form of separation. Hierarchs and theologians from both sides have fully, formally, and officially agreed that what the Oriental Orthodox mean when they say “from two Natures” is equivalent to what the Catholics mean when they say “in two Natures.” The method of agreement was the realization that,
“Pegging down orthodoxy to…the fixity of theological propositions issued by them, and judging orthodoxy or otherwise of a section of the church on the basis of its acceptance or rejection…has failed to produce unity in the Church, and most probably will continue to do so…On the other hand, when we take a Council dealing with doctrinal matters as a teaching organ, rather than a legislative organ of the church, and focus our attention on the insights contained in its exposition, then the desired consensus will be possible to produce.”
HG Archbishop Tiran Nersoyan (of happy memory) of the Armenian Apostolic Church
So not only are Miaphysite Catholics in full agreement with the infallible Magisterium of the Church, I believe our existence is necessary to demonstrate in a palpable way the fact that Miaphysites and Diophysites are truly united in Christology, and to witness to the value of the spiritual fruit of understanding as the only and truest method to achieve unity among the Churches.
I hope I have answered your question sufficiently. Or feel free to ask any other questions.