One literary technique Chaucer uses is to have the Wife of Bath's tale illustrate her contention that what women most want is to be in control. This magical tale from King Arthur's court shows literature as wish fulfillment. In the story, a knight rapes a lady. Guinevere sits in judgment and tells him he has a year and day to determine what it is women really want. The knight asks and asks, and finally, in desperation, agrees to give an old hag whatever she wants in return for the answer. She tells him that what women most want is power over their husbands: this is correct. The man has to marry the hag. He then finds that he has a choice: the old hag can be young and beautiful by day and ugly by night. If she is beautiful by day, the knight will gain status in the eyes of the world, if beautiful by night, the sex will be good. The knight doesn't know which choice is best and tells her "you decide." This exactly illustrates what the Wife of Bath wants from a spouse—the power to make decisions. The knight is rewarded for giving decision-making power to his wife by having her become beautiful all the time.
Thus, the Wife of Bath uses the literary device of a story to make a point about female power. Does every woman really want power over her husband as the end all and be all? The audience doesn't know, but they know it is what the Wife of Bath wants.
Chaucer also has the Wife of Bath tell us about her life and marriages in the Prologue (her background being the longest of any character) to show that having power and control is crucial to her. As she describes it, she will stop at nothing to hold the power in the marriage. She openly advocates lying, saying women are better at this than men. She says wives should accuse men of having affairs and have their maids back them up. This keeps the men off kilter and on the defensive. She is willing to go to almost any length to gain control—for example, she rips three pages out of one of her husband's book, damaging what was a very expensive item at the time, to get her way. She is unstoppable until she is in charge.