In Mary Shelley's "Frankenstein," what part of the creature's tale persuaded Victor to consent to its request for a companion?
"Hateful day when I received life!" I [the Creature] exclaimed in agony. "Accured creator! Why did you form a monster so hedeous that even you turned from me in disgust? ... Satan had his companions, fellow devils, to admire and encourage him, but I am solitary and abhorred. ... no Eve soothed my sorrows nor shared my thoughts; I was alone. I remembered Adam's supplication to his Creator. But where was mine?"
I suspect this argument (and others) appealed to Victor's sense of guilt. He had assumed the role of god when he created a life from nothing. The Creature reminds him that the "real" God, when he saw that he had made man and left him alone, created a partner for him. If God saw this and acted, how could Victor do less?