For Christ is God by the grace of union. But Christ, as Man, has the grace of union. Therefore Christ as Man is God.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic union God
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/19950/pg19950-images.html

Context

“Hence it does not follow that, if He is a creature as Man, He is a creature simply. _______________________
ELEVENTH ARTICLE [III, Q. 16, Art. 11]
Whether This Is True: "Christ As Man Is God"?
Objection 1: It would seem that Christ, as Man, is God. For Christ is God by the grace of union. But Christ, as Man, has the grace of union. Therefore Christ as Man is God. Obj. 2: Further, to forgive sins is proper to God, according to Isa. 43:25: "I am He that blot out thy iniquities for My own sake." But Christ as Man forgives sin, according to Matt. 9:6: "But that you may know that the Son of Man hath power on earth to forgive sins," etc.” source