How the assertion that a man was assumed is to be understood.
Likewise perplexing in the same discourse by Athanasius is the assertion that man is assumed. Speaking in the person of the Son he says: “Having assumed man in full I have given the Holy Spirit fully and perfectly to men.” And in his letter to Serapion he states: “The unity of the Church is from the Father through the Son in the Holy Spirit through the deifying and deified man, assumed by the same Son.”
It should be noted, however, that since no one assumes himself, the one assuming must be distinct from what is assumed, the recipient from what is received. If, therefore, man is said to be assumed by the Son of God, what is connoted by the term man must be diverse from what is connoted in the term Son of God. By the term man, however, can be connoted either a complete human person, or less: a human supposit not enjoying human personhood. If, therefore, the statement should be made that a man is assumed, where man connotes a human person, it will follow that a divine person has assumed a human person, and thus there will be two persons in Christ, which is the Nestorian heresy. Augustine, therefore, says in his book De fide ad Petrum that “God the Word did not take to himself the person of a man, but the nature.”
Some, wishing to avoid this error, have said that when a man is said to be assumed by the Word, by the term man is understood a supposit of human nature, namely, this man, but not a human person, because it does not exist separately of itself, but is united to someone of greater dignity, namely, the Son of God. And because this human supposit, which is designated as assumed when the phrase: assumed man, is used, is distinct from the supposit which is the Son of God, they affirm that these are two supposits in Christ, but not two persons.
But on this view, it follows that this proposition: the Son of God is a an, would not be true. For it is impossible that of two things different from one another as two supposits one could truly be predicated of the other. And, therefore, it is commonly held that there is but one supposit connoted by the term man and the term Son of God. From this it follows that the statement: man is assumed, is false or imprecise. It should be interpreted to mean: The Son of God assumed man, that is, human nature.