The Angelic Doctor Against the Errors of the Greeks - Chapter 21

How the assertion ‘God made man God’ is to be understood.

Another doubt arises from what Athanasius says in the same letter: “The Son of God, assuming man in his own hypostasis in order that he might lead man back to himself, made him God, deifying him.” And in his third discourse on the Council of Nicaea: “It is impossible for them to be consummated unless I assume a perfect man and deify him and make him God with me.” By this it is implied that the proposition: man has become God, is true.

It is to be noted  that the propositions: God was made man, and man was made God, are equally true according to the opinion which claims there are two supposits in Christ, for when it is said: God was made man, from that point of view, is that a supposit of divine nature was united to the supposit of human nature: and conversely, when it is said that man was made God, the sense is that a supposit of human nature was united to the Son of God.

But if it is maintained that in Christ there is but one supposit, then the statement: God was made man, is true in the proper sense, because he who was God from eternity began to be man in time. Properly speaking, however, this proposition is not true: man was made God, because the eternal supposit connoted by the term man was always God. Hence, the passages of Athanasius are to be explained thus: man was made God, that is, it came to be that man is God.