In The Canterbury Tales, what does the old wife say that convinces the knight to leave it up to her?
First of all, the knight is a rapist who has been saved by the women and queen. His task is to find out what women desire most. However, after a year of searching, he must return and admit defeat. Luckily, the old wife gives him the answer: "What women most desire is sovereignty Over their husbands or the ones they love, To have the mastery, to be above" (138-140).
What he doesn't know is that the price of the answer is marriage to the old wife. He finds her both old and poor - two characteristics he cannot handle. She launches into a diatribe about how nobody can choose nobility or poverty and how the elderly are wiser through experience.
Luckily, she presents him with a choice: she will stay old and ugly but a perfect wife or transform into a beautiful young girl who might cheat on him. Her argument is "If I am old and ugly, as you've said, Of cuckoldry you needn't have a dread; For filthiness and age, as I may thrive, Are guards that keep one's chastity alive" (1213-1216).
His fear of being cuckolded, a very real consequence for men, makes him wonder what to choose. Then he remembers his initial lesson - let the women have power over men. He lets her choose and is rewarded with a young, beautiful and faithful wife.