St. Thomas seems to say that the Son of God would not have been incarnate if man had to sinned. But Bl. John duns Scotus seems to think that he would have been incarnate just out of love for humanity. Why Thomas' thought?
Its an open theological question and theologians are free to take any side they want in this debate. Thomas Aquinas simply argued that no other reason is given in Scripture for the Incarnation other than “saving the lost.”