What is the most suitable title: "She Stoops to Conquer" or "The Mistake of the Night"?
She Stoops to Conquer was originally titled The Mistake of the Night. She Stoops to Conquer is a far better title, in my opinion, because it is catchier and because it more clearly expresses the subject and theme of the play.
The words "she stoops to conquer" come from a Dryden poem. The juxtaposition of two words with opposite connotations, "stoop" and "conquer," piques our interest. Normally people don't "stoop," which is a symbol of abjection and surrender, in order to "conquer" or win. We immediately wonder what is going on.
The title exactly captures the core of the main plot in a way the original title doesn't: Kate Hardcastle realizes that her love interest, Marlow, is afraid of women of his own class, but bold and flirtatious with lower-class women. Kate decides to "stoop," to pretend to be a lower-class maid, in order to "conquer" Marlow's heart. This ruse wins the day.
The seeming contradiction or oxymoron in the words "she stoops to conquer" also represents the zany, madcap, upside-down world of the play, where Marlow and his friend George Hastings believe the Hardcastle estate is an inn, Kate, a woman, takes control of the wooing, and little is at it seems.
Well, in my personal opinion, She Stoops to Conquer is a much more artistic and clever title for this play. The Mistake of the Night is okay—but which mistake? Marlow's belief that Constance is a barmaid? Mrs. Hardcastle's lie about the missing jewels? The fact that they turn out to truly be missing?
The term stoops is great—it means to lower something or someone. Kate lowers herself to the position of a working-class woman to test Marlow's feelings for her. Marlow is uptight around women of the higher classes and is not himself. But working women were subjected to the sexual advances of men and more often able to see their true nature. Kate stoops to find the real Marlow.
Kate also stoops to deception. She chooses to play a role to sneak a peek into Marlow's real nature. It is a risky choice, because if the relationship works out, she has started it with a lie. It could have backfired on her, as well. Marlowe could have been incensed that she put one over on him and never talked to her again.
But, in the end, She Stoops to Conquer is the right title, because by lowering her status, Kate finds out that the real Marlow is someone she can love.