Cléante confronts Tartuffe and suggests that it is not the act of a religious man to cause such strife in a family and to allow a father to disinherit his son. Tartuffe argues that he would love to see Damis reinstated, but he is afraid that people would then interpret his act incorrectly. Cléante points out the warped reasoning in this argument and suggests that he leave vengeance to God. Tartuffe maintains that he has forgiven Damis but finds it wrong to live with someone who smears his name. He also explains that he despises wealth and the only reason he allows Orgon to transfer his property to him is so that it will not fall into wicked hands where it might be used for crime and sin. When Cléante begins to point out the fallacy in this argument, Tartuffe leaves abruptly, saying that he has to attend to certain pious offices.
Elmire, Mariane, and Dorine arrive, asking Cléante to stay and help them convince Orgon of his errors. When Orgon arrives, he presents Mariane with the marriage contract. She pleads on her knees that he not force her to marry Tartuffe; she says she does not resent her father's love for Tartuffe and, if he wishes, Orgon can take all of her property and bestow it on Tartuffe, but she requests that she be left free to choose a husband for herself.
Orgon argues that the more one loathes a man the more noble it will be to marry him because, by so doing, one will be able to mortify one's flesh and make it pure. Cléante starts to offer advice, but Orgon tells him that even though his advice is sound, he will not follow it. Elmire is astounded at Orgon's ability to be continually wrong. She wonders if he would believe his eyes and challenges him to become a part of a plot which would reveal Tartuffe's hypocrisy. Orgon has such faith in Tartuffe that he accepts the challenge.
Elmire sends the others away and tells Orgon to hide under the table and to observe what is about to take place. She asks him to interrupt the interview between her and Tartuffe at any moment that he is convinced that Tartuffe is not the man he pretends to be.
In all of Molière's plays there is always at least one character who represents the voice of moderation and rationality, qualities which were greatly admired by the age during which Molière lived. At the beginning of Act IV, it is obvious that Cléante functions as the expression of the reasonable view. In talking with Tartuffe, Cléante displays unassailable logic. He points out that Tartuffe is not acting as a truly religious person should and also demonstrates that Tartuffe's logic is faulty. For example, when Tartuffe tries to justify his taking Orgon's money and property so as to keep it from falling into wicked hands, the irony is double here because there are no more wicked hands than his for it to fall into; then, when Cléante reasons that the burden of handling such money should belong to Damis, that the son should be allowed to bear the burden, and that true religion does not demand that a person be disinherited, Tartuffe is unable to withstand this onslaught of logical consistency. Thus, as Cléante begins to trap Tartuffe by sound reasoning, Tartuffe suddenly realizes his danger and leaves with the hypocritical statement that he has to attend to some pious duties.
Throughout the scene, Cléante does not realize that he is dealing with an unmitigated scoundrel and part of the comedy of this scene depends upon how the scoundrel cleverly escapes the rationalist's traps.
The entire situation becomes more desperate as Orgon insists upon the marriage taking place that very night. This forces everyone concerned to create some plan of action so as to undeceive Orgon.
Mariane's plea to her father to be spared such horror as marriage with Tartuffe arouses the first real note of feeling in Orgon. But, like a true religious fanatic, he forces himself to put aside his more humane values and adhere absolutely to his own religious views. Ironically, his statement that one should mortify the flesh in order to purify it is a strong principle of many religions. The intentional mortification of the flesh is often one of the customs of some monasteries and nunneries and is consistent with many other religious practices. Such statements as these spoken in such an absurd context also contributed to the censoring of the play.
This scene (Scene 3) also contributes to the exposure Orgon's absurdity. For example, when he tells Cléante that though Cléante's advice is correct, he will not follow it, then we begin to doubt Orgon's sanity.
Elmire, who, along with Cléante, represents the true voice of reason, must now step in and bring an end to the absurdity. When she says that she is astounded at Orgon's capacity to be wrong, she expresses the thoughts of all the readers and the audience. Orgon refuses to believe her accusations about Tartuffe because, earlier, Elmire had refused to be indignant. In true rational fashion, Elmire explains that she dislikes the type of prudish woman who screams about any flirtation. She herself offers a polite and distant rebuff and, therefore, is never involved in an embarrassing position.
In spite of all of Elmire's explanations, Orgon refuses to accept her story. When she challenges him to be present at a scene where she can reveal the fact that Tartuffe is a hypocrite, Orgon accepts the challenge only because he is certain that he is right. Elmire is, however, confident of the outcome because she knows that lustful men such as Tartuffe can easily be trapped by their passions.