John of Damascus: Exposition of the Orthodox Faith 60In reply to those who say “If man has two natures and two energies, Christ must be held to have three natures and as many energies.”

Each individual man, since he is composed of two natures, soul and body, and since these natures are unchangeable in him, could appropriately be spoken of as two natures: for he preserves even after their union the natural properties of either. For the body is not immortal, but corruptible; neither is the soul mortal, but immortal: and the body is not invisible nor the soul visible to bodily eyes: but the soul is rational and intellectual, and incorporeal, while the body is dense and visible, and irrational. But things that are opposed to one another in essence have not one nature, and, therefore, soul and body cannot have one essence.

And again: if man is a rational and mortal animal, and every definition is explanatory of the underlying natures, and the rational is not the same as the mortal according to the plan of nature, man then certainly cannot have one nature, according to the rule of his own definition.

But if man should at any time be said to have one nature, the word "nature" is here used instead of "species," as when we say that man does not differ from man in any difference of nature. But since all men are fashioned in the same way, and are composed of soul and body, and each has two distinct natures, they are all brought under one definition. And this is not unreasonable, for the holy Athanasius spake of all created things as having one nature forasmuch as they were all produced, expressing himself thus in his Oration against those who blasphemed the Holy Spirit: "That the Holy Spirit is above all creation, and different from the nature of things produced and peculiar to divinity, we may again perceive. For whatever is seen to be common to many things, and not more in one and less in another, is called essence. Since, then, every man is composed of soul and body, accordingly we speak of man as having one nature. But we cannot speak of our Lord's subsistence as one nature: for each nature preserves, even after the union, its natural properties, nor can we find a class of Christs. For no other Christ was born both of divinity and of humanity to be at once God and man."

And again: man's unity in species is not the same thing as the unity of soul and body in essence. For man's unity in species makes clear the absolute similarity between all men, while the unity of soul and body in essence is an insult to their very existence, and reduces them to nothingness: for either the one must change into the essence of the other, or from different things something different must be produced, and so both would be changed, or if they keep to their own proper limits there must be two natures. For, as regards the nature of essence the corporeal is not the same as the incorporeal. Therefore, although holding that man has one nature, not because the essential quality of his soul and that of his body are the same, but because the individuals included under the species are exactly the same, it is not necessary for us to maintain that Christ also has one nature, for in this case there is no species embracing many subsistences.

Moreover, every compound is said to be composed of what immediately composes it. For we do not say that a house is composed of earth and water, but of bricks and timber. Otherwise, it would be necessary to speak of man as composed of at least five things, viz., the four elements and soul. And so also, in the case of our Lord Jesus Christ we do not look at the parts of the parts, but at those divisions of which He is immediately composed, viz., divinity and humanity.

And further, if by saying that man has two natures we are obliged to hold that Christ has three, you, too, by saying that man is composed of two natures must hold that Christ is composed of three natures: and it is just the same with the energies. For energy must correspond with nature: and Gregory the Theologian bears witness that man is said to have and has two natures, saying, "God and man are two natures, since, indeed, soul and body also are two natures." And in his discourse "Concerning Baptism" he says, "Since we consist of two parts, soul and body, the visible and the invisible nature, the purification is likewise twofold, that is, by water and Spirit."