These words sound like something out of a physics textbook. In fact they describe two ways of thinking and speaking about the Lord Jesus Christ regarding the union and distinction between the divine Logos and his humanity.
Historically the Christian Church was divided by the Council of Chalcedon. Both sides agreed, and still do, that Christ is one person in which perfect divinity and perfect humanity are perfectly united. The difference lay in the terminology used by Chalcedon to describe this union. The monophysite (one nature) churches could not agree to the wording, so they withheld their consent. They were the African Churches of Egypt and Ethiopia, the Syrians, Armenians and the Indians. The diophysite (two natures) churches were the Western and Orthodox churches, and since then, the Protestant churches.
It may sound like a stupid argument about words, not substance, but there is a real and valid point to the Monophysite objection.
They argue that St. Cyril has taught us that since the incarnation it is wrong to speak of Christ as if he is two, and not one. For example, it is wrong to say that he is God and man, since that is to speak of two entities. Rather we should speak of the incarnate God, since that is to speak of a single entity, a single person.
They use the example of burning iron. One does not speak of it as fire and iron, but as one thing. To do otherwise is unnatural. Man is a perfect union of body and soul, yet we do not speak of man as body distinct from soul. When you have indigestion you do not say, “My body is feeling discomfort but my soul is not”. That is an absurd mode of speech.
There is a far more serious reason not to speak of the incarnate God in this way. Nestorianism teaches that Christ’s deity and his humanity are so distinct that they are in effect two persons. There is a divine person and a human person, but the union is hardly a union at all. The argument is that when Chalcedon speaks of Christ in these dualistic terms, even though they formally affirm the perfect union, they are thinking in a way that has very strong Nestorian tendencies, a way that is unnatural, and a way of thinking about the two natures that is heretical, because it is so much like Nestorianism.
If we are to speak of the Hypostatic Union even the language employed must avoid Nestorian-like modes of speech and categories of thought.
To be continued …