The reader of the play sometimes forgets that the audience would be fully aware that Damis is hiding during this scene and is thus overhearing everything that Tartuffe says to Elmire. This comic technique, called the comedy of concealment, is often used by Molière.
Molière is careful here not to make Tartuffe a hypocrite in the abstract. Tartuffe is very human, a man who has all the basic impulses of any person, and the interest of the play lies partly in the fact that his own passion and desire for Elmire is the flaw that lets him forget his ultimate plan and causes him to abandon the careful disguise he has so far maintained.
Earlier in the play, Dorine had hoped that Elmire could have some influence over Tartuffe, but Tartuffe's passion for Elmire comes as a surprise to us. The manner in which he cannot control his passion and the way he pursues Elmire, who constantly rebuffs him, constitute the essential comedy of this scene.
Tartuffe's hypocrisy — once vicious — now becomes comic as we see the absurd manner in which he uses reverse logic to suggest that a woman is safe in having an affair with a pious man because the pious man himself must be careful to protect his name. Tartuffe's passion, furthermore, is so intense that he cannot discern that Elmire finds him repulsive.
Elmire's primary role is to get Tartuffe to repudiate the marriage between himself and Mariane. To accomplish this, she allows Tartuffe to proceed so far in revealing his love, but rather than making a scene about it or actually revealing his hypocrisy to her husband, her first desire is to prevent the impending marriage. Damis' arrival, with his hot-tempered determination to reveal Tartuffe's treachery, spoils the more reasonable plan put forward by Elmire. Elmire's view is the more rational view as she maintains that a woman should not run and tattle to her husband every time a man makes an overture to her.
