The Doctor and Nora's conversation about love and life makes Nora realize humans eternal conditioned state:
barnes writes, "conditioning himself to fear, made God; as the prehistoric, conditioning itself to hope, made man - cooling of the earth, the receding of the sea. And I, who want power, choose a girl who resembled a boy" (barnes 145). Nora has been conditioned to look for a man, but since she is in love with Robin, she believes their must be some manly qualities about her that drew her in, in the first place.