In my last section of Aquinas for 2014, I encountered the Doctor engaging in some hypothetical speculation. The Incarnation is a subject of great mystery. How could and did God take on human nature? The details lie as far out of reach of the human intellect as the Japanese shore to the eyesight of a boater sailing off Catalina. But just as the Californian can point the way to Japan without seeing it, so Aquinas can speak up to the limits of our comprehension on the union of God and Man. But it seems to me he goes still farther, even admitting at one point after arguing one particular doctrine that various opinions exist among the learned faithful.
Some things the Christian can state with certainty: God did not change when He took human form; human nature changed. Broken humanity needed the Incarnation as the means of restoration; only God could bring the remedy, and only a man could satisfy justice. As a man, Christ had a true body and a soul, and as God, his soul was perfect.
Aquinas also addresses some issues raised by many of the early heresies in this section and clarifies them for me by bringing them together in this context. The Word of God assumed human nature, not a human. In other words, God didn’t pick a child named Jesus and then do something to him; Jesus was divine and human from the moment of conception. His body was not imaginary, as Manes taught. (This is the Manes whose teaching Augustine followed for a while before becoming a Christian.) His body consisted of earthly elements; it was not a heavenly body, as Valentine taught (the Gnaostic heretic, not the saint). He did not take on a body only, as Arius taught.
But then Aquinas goes further by delving into hypothetical ground. Would Christ have come to earth if people had not sinned? No, says Aquinas, there would have been no need. Could any of the three Divine Persons – even the Father or the Holy Spirit – have assumed human nature? Yes. Could more than one Divine Person have taken on human nature at the same time? Yes. Could one Divine Person have taken on two human natures? Yes. I don’t know what Thomas gets out of establishing that last one. But the other tenets allow him to praise the fitness of the Word, and the Word only, having assumed nature. As He through whom all things were created, the Word saw his human creation fall. So his Incarnation allows the Craftsman (Aquinas’s word) to restore his own work. Wisdom is ascribed to the second Person especially, so his Incarnation allows Wisdom to complete the destiny of rational creatures. And He is Knowledge, who in restoring humanity restores the race that fell by seeking knowledge. These conclusions inspire me, so to my view, the hypothetical speculation was completely justified.