St. Cyril of Alexandria (376 – 444) – was Patriarch of Alexandria 412-444 and articulated the highest Christology of the undivided Church.

“Godhead and manhood are one thing and another, according to the mode [of being] existing in each, yet in Christ have they come together, in unwonted wise and passing understanding, unto union, without confusion and turning [τροπῆς] . But wholly incomprehensible is the mode of the Union.”
– From “On the Unity of Christ“