When once this knot of doubt or ambiguity has been untied, nothing further can be advanced to shake the true and solid content of the Catholic Faith, which is that the same Christ is perfect man and God, and that He who is perfect man and God is One God and Son of Man, that, however, quaternity is not added to the Trinity by the addition of human nature to perfect Godhead, but that one and the same Person completes the number of the Trinity, so that, although it was the manhood which suffered, yet God can be said to have suffered, not by manhood becoming Godhead but by manhood being assumed by Godhead. Further, He who is man is called Son of God not in virtue of divine but of human substance, which latter none the less was conjoined to Godhead in a unity of natures. And although thought is able to distinguish and combine the manhood and the Godhead, yet one and the same is perfect man and God, God because He was begotten of the substance of the Father, but man because He was engendered of the Virgin Mary. And further He who is man is God in that manhood was assumed by God, and He who is God is man in that God was clothed with manhood. And although in the same Person the Godhead which took manhood is different from the manhood which It took, yet the same is God and man. For if you think of man, the same is man and God, being man by nature, God by assumption. But if you think of God, the same is God and man, being God by nature, man by assumption. And in Him nature becomes double and substance double because He is God- man, and One Person since the same is man and God. This is the middle way between two heresies, just as virtues also hold a middle place.[75] For every virtue has a place of honour midway between extremes. For if it stands beyond or below where it should it ceases to be virtue. And so virtue holds a middle place.