In both plays, the asides allow characters to reveal their true feelings to the audience. In Tartuffe, some of the asides come from Dorine, who is a sharp commentator on the weaknesses of her "betters." She is able to reveal with her asides, for instance, that she sees straight through Tartuffe. In one aside, after Tartuffe comes in declaring he has just distributed money to poor people on the street, Dorine says:
Dear God, what affectation! What a fake!
In The Misanthrope, Alceste also reveals his true feelings through asides. For example, after Philinte praises Oronte's sonnet, Alceste says to him as aside:
Good heavens! Vile flatterer! You're praising rubbish.
Alceste, however, reveals himself as overly harsh and unable to get along in society through his asides, while Dorine shows a level-headed good sense.
Asides are also used to create dramatic irony, which occurs when the audience of a play knows what the characters do not. In Tartuffe, for example, the asides of both Mariane and Valere show they doubt the other's love. Mariane says as an aside:
He hates the sight of me, that’s plain. I’ll go, and so deliver him from pain.
Valere says as an aside:
She cannot bear my presence, I perceive. To spare her further torment, I shall leave.
But neither Mariane and Valere knows the other's feelings. It takes the level-headed Dorine to realize what is going on and bring the two together.
Dramatic irony occurs as well in The Misanthrope. When Alceste sees Celimene, he says as an aside:
O heaven! Can I be master of my passion?
This shows that he feels deeply about her, a fact she does not know. She has to question him to try to interpret "meaning of your deep-drawn sighs."
In both plays, asides help tell us things we might not otherwise know about a character's thoughts or feelings. However, only in The Misanthrope do we have a long aside that acts as a soliloquy as Alceste explores his ambivalent emotions towards Celimene in act IV, scene 3, a mixture of annoyance at her for blaming him for what he feels is not his fault and besotted love and hope.