What are miaphysitism and dyophysitism?
Both words are labels from the early church's long argument about how Godhead and manhood meet in Jesus Christ: mia/mono-physis means "one nature," dyo-physis means "two natures." The question behind the labels is simple to state and impossible to exhaust — when the Word became flesh, did the two natures blend into a single new one, or do they remain distinct in one undivided Person?
The one-nature position
The writers in this collection use the older names for the view: Monophysite, or Eutychian, after Eutyches. One of them quotes the sentence from Cyril that the one-nature party always appealed to, and it is the formula in its clearest form:
J. N. DarbyThe Eutychians always appealed to Cyril's famous sentence: "The union was made out of two natures; but after the union there was one nature of the Word incarnate in Christ." … No one can doubt that Eutychianism (the doctrine of one nature in Christ) and the Jacobite church of Alexandria were the fruit of Cyril's doctrine.
This was never a fringe opinion. It became the confession of whole national churches that still exist:
Church HistoryUnder the general name of Monophysites are included the four main branches of separatists from the Eastern church: the Syrian Jacobites, the Copts, the Abyssinians, and the Armenians. The founder of this large and powerful Christian community was Eutyches, abbot of a monastery in Constantinople in the fifth century. The Monophysites denied the distinction of the two natures in Christ; the Monothelites denied the distinction of the will, divine and human, in the blessed Lord.
The two-natures answer
The rival position was settled at the Council of Chalcedon, and one writer sets it in the line of failed attempts that came before and after it:
The Bible TreasuryApollinarianism pruned away part of Christ's humanity, leaving out a rational human soul, mainly to keep His personality single. Nestorianism brought the two natures into no more than sympathetic harmony with each other, and by holding them too far apart the Person was no longer an unbreakable unity. Eutychianism, in exactly the opposite direction, merged the two natures into one compound — a confusion not at all balanced out by the single personality it still kept. The statement of the Council of Chalcedon puts forward no theory; it simply asserts the unity of personality and the duality of natures.
Not a blend of the two
Where the union is located matters. It is not in the substance but in the Person:
Truth & TestimonyThe opposite error to saying that He is two Persons is to say that His two natures have combined into one. It was an ancient heresy that the two natures, Manhood and Deity, merged together. … He is wholly Man and wholly God. He possesses all the attributes and properties of real, unfallen, holy Manhood, and at the same time possesses all the infinite attributes and properties of Deity. The unity consists, not in the merging of essence, but in the Oneness of His Person.
What fusion would cost
The objection is not merely that fusion is untidy. It removes the very manhood Scripture insists on:
W. R. DronsfieldThe unity of the Godhead and Manhood is not by confusion or fusion of substance; otherwise the substance of manhood would be raised to something more than true humanity. ("In all things it behoved Him to be made like unto His brethren," Heb. 2:17.) This false explanation of the Incarnation, attempted by human intellect — that the union of Godhead and Manhood in Christ is by a confusion of substance — must be rejected. We can say that the union of the natures consists in the Unity of the Person who possesses both.
(ESV: "he had to be made like his brothers in every respect.")
The error on the other side
Confessing two natures carries its own danger, and the commentators weigh the two failures as equally fatal:
William KellyThe Nestorianism that divides the Person is as dangerous and destructive as the Eutychianism that confounds the two natures, to the ruin of both. From the conception, Deity was never separated from the humanity of Christ — not even when His spirit was in Paradise and His body lay in the tomb.
Where the analysis has to stop
Each of these systems began as an attempt to make the mystery manageable, and that is precisely the objection raised to all of them:
The Bible TreasuryIt is the union of the divine and the human in His blessed Person that is unknowable. Every kind of ingenious speculation has been exhausted trying to analyse it. In vain! No such unassailable tower ever rose four-square to heaven. The would-be interpreters are always baffled, and the burning of their own fingers is the smallest part of the damage.
Summary
- One Person. Every sound statement starts here: not two Christs, but one undivided Person who possesses both Godhead and manhood.
- Two natures. Chalcedon offered no explanation — it only affirmed the single Person and the twofold nature, and left the mystery standing.
- Not merged. The one-nature view, held by Eutyches and by the Coptic, Armenian, Syrian and Abyssinian churches, makes the natures into one; the unity, say these writers, lies in His Person, not in a blended essence.
- Not divided. Splitting the natures apart is judged just as ruinous as fusing them; Deity was never separated from His humanity, not even in death.
- Not explained. If the natures fuse, His true humanity is lost — and if we try to analyse the union, we lose our footing entirely. The Father alone knows the Son.