Question 6. The order of assumption
Here, Thomas’ teaching on potency and act, and more specifically, form and matter is key. Matter is pure potency, but never exists without a form. It is actualized by one form or another. A human body, as matter, is not a human body without the form of the body, the soul. This must be kept in mind throughout.
Article 1. Whether the Son of God assumed flesh through the medium of the soul?
Having established, in Question 5, Christ was true man, including all that that entails, he proceeds here to establish the same in the order of causality. The soul is the form of the body. It is what “makes the human body to be a human body.” It is not prior in time, but it is prior in causality. Therefore, the flesh is assumed through the medium of the soul.
Article 2. Whether the Son of God assumed a soul through the medium of the spirit or mind?
Again the objections are based on a false understanding of the human soul, and Thomas’ corrections likewise demonstrate the proper understanding.
The human soul, in earlier Christians, was often though to be three rather than one; the vegetative, the sensitive, and the rational. In reality, the two lesser powers are powers of the one soul, the rational. The rational soul, containing then also these “lesser” powers, is yet one, and it is the form of the body.
It is through the intellect, then, that Christ assumes the soul, because in a human soul, the intellect is prior, again, in causality, as it is the reason for the lesser powers of the same soul.
Article 3. Whether the soul was assumed before the flesh by the Son of God?
Thomas now makes clear that the distinction of cause does not cause a difference in time. The priority in causality in assuming the body through the soul does not mean it happens prior in time to the same. We can see a similar argument used by Thomas in his work “On the Eternity of the World,” a wonderful short document that demonstrates this difference, among many other wonderful gems of reasoned argument.
As I said earlier, we again see some residual Platonism appear, and Thomas responds to it. He mentions specifically Origen, who held the Platonic belief in the creation of all souls from the beginning. This would indeed make the soul prior in time to the body, and although the soul is a soul of “this body” and can exist apart from the body, it is not natural that it do so. When a human is created, the body and the soul come together at once and man is created. We also see the revealed truth of the resurrection of the body; body and soul belong together, and this is contrary to the Platonic theory of souls pre-created.
Article 4. Whether the flesh of Christ was assumed by the Word before being united to the soul?
The answer is no, and the same principle is used once again. Matter is pure potentiality, but never exists without being informed, that is, without having some form. Now, the moment that matter that was potentially a human receives a soul, it becomes human; not before or after.
If the Son of God was united to the body before being united to the soul, He would not have assumed a human nature, but rather the “components” of a human body. But our faith is that He, at one instant, assumed a human nature. Christ therefore assumed a complete human nature, which must include both its matter and form: the body and soul.
Article 5. Whether the whole human nature was assumed through the medium of the parts?
Thomas here continues to show the order of causality and the order of time, and that they differ. The soul is first in order of causality, for it is what makes “this matter” to be a human, although it is not human first before informing “this matter.” It is one substantial being, and it is thus not assumable in parts, but as the substance that it is. It is a human nature that was assumed, not a body and some separate soul. For if these were “parts” then parts were assumed, rather than a human nature.
“For us and for our salvation he came down from heaven: by the power of the Holy Spirit he became incarnate from the Virgin Mary, and was made man.”
He did not assume “parts of man,” but became man. Man is at once the soul which informs it and the body that the soul informs.
Article 6. Whether the human nature was assumed through the medium of grace?
The Person of Jesus Christ is where the union took place, as was established earlier. Created grace, which is an accident (metaphysically) cannot be the means by which the existence of the true God is united and really becomes man. It is a substantial union, and the union is in the eternal and uncreated Person of the Son. Therefore, if “through the medium of grace” we mean that same grace that adheres in the soul’s of the saved, then it cannot be this created grace.
If, however, we mean that grace that is the eternal love of God and likewise His eternal providence, then indeed this grace is the efficient cause of the union of the Son and the human nature. Created grace would be a [temporal] means, and this we reject. Eternal grace is the “mover” and reason of the union, and this we affirm.