In the prologue, Congreve uses verbal irony (saying the opposite of what he means, through the actor who plays Fainall) to set up the witty satire that is about to follow:
Satire, he thinks, you ought not to expect;
For so reformed a town who dares correct?
To please, this time, has been his sole pretence;
He’ll not instruct, lest it should give offence.
Should he by chance a knave or fool expose,
That hurts none here, sure here are none of those.
In short, our play, shall (with your leave to show it)
Give you one instance of a passive poet.
Who to your judgments yields all resignation;
So save or damn, after your own discretion.
This sounds at first like the highest flattery of the audience. Congreve claims his play is not like other Restoration comedies, which satirize society, because the audience is "reformed" and surely beyond reproach. He does not mean to "give offence" by "instructing" them in how to behave because they already know how to behave. He admits that he might "expose" some of the characters as fools, but he insists that these foolish characters do not reflect anyone who is in the audience. Congreve presents himself as a "passive poet" (rather than an active satirist) who just wrote a play for fun and is presenting it to the audience. They are free to judge the characters as they wish. In fact, Congreve suggests that the audience probably knows better than him which characters ought to be judged.
But Congreve does not really intend this prologue as straightforward flattery. The first clue to this is that the actor who plays Fainall, a chronic liar and manipulator, delivers the speech. By getting the audience to believe they are beyond reproach, Congreve has already gained a point against them. As the play goes on, it becomes clear that only a fool, like Lady Wishfort, can be taken in by this kind of flattery. The play goes on to critique a society of "manners" where people avoid "giving offence" openly by making backhanded compliments and performing politeness more than embodying it. Congreve is having his own fun with performing manners. The prologue sounds extremely polite but is itself one long backhanded compliment.
Nonetheless, the prologue does soften the blows of the play's satire. The fact that Congreve makes fun of his audience by doing exactly what he critiques (couching criticisms in politeness) establishes right away that the satire is good-natured. He is not above is own critique, and he thinks the pettiness of all this "polite" rudeness is at least as amusing as it is bad for society.
In Act 3, Scene 4, Wishfort tells Marwood to hide in her closet (more of a study than a storage room in this context) while she speaks to Foible and tries to see if Foible and Mirabell are up to something. Wishfort alludes to several moralist works, all on the bookshelf in the closet for Marwood to peruse:
Dear friend, retire into my closet, that I may examine her with more freedom. – You’ll pardon me, dear friend; I can make bold with you. – There are books over the chimney – Quarles and Prynne, and the Short View of the Stage, with Bunyan’s works, to entertain you.
Quarles is a poet whose most famous work, Emblems, dressed up scripture in ornate paraphrases. Critics such as Alexander Pope and Sir John Suckling (who Millamant later quotes) hated Quarles and thought his work was a pointless embellishment on ideas readers could get by reading the Bible directly. Like many of the people in Congreve's play, Emblems makes a flashy show of its moral superiority rather than saying anything especially important or new. Meanwhile, Prynne and Jeremy Collier (who wrote A Short View of the Immorality and Profaneness of the English Stage in 1698) had both critiqued the theater for promoting bad morals. Collier had specifically called out Congreve and several other playwrights for their plays' failure to punish characters for their sins. Bunyan is John Bunyan, who wrote Pilgrim's Progress, one of the most commercially successful Christian allegories ever. Reading Pilgrim's Progress was fashionable for a long time, and readers could appear to be devout Christians simply by showing that they had read this book.
These allusions contribute to the play's satire. Lady Wishfort is one of the immoral characters who, according to Collier's argument, ought to be punished. The fact that Lady Wishfort herself is representative of the kind of people who like these moralist works reveals a lack of reflection on moralists' part. Like Quarles's dressed-up scripture, Lady Wishfort's bookshelf is a display of morals more than morality in practice. The people who read and write these books, Congreve implies, aren't actually any better than anyone else. In fact, they are often worse because they are hypocrites who perform moral superiority without understanding or really embodying it.
Congreve's prologue indicated that the play would not make fun of audience members because surely everyone in the audience is beyond reproach. Those audience members who saw through the verbal irony of the prologue, concluding that no one is truly beyond reproach, are in on the joke here. They understand that Lady Wishfort is just like those audience members who believe that they actually are beyond reproach.
In Act 3, Scene 18, Fainall tells Marwood that cheating on his wife is honorable because it takes place within marriage, an "honourable" institution. Fainall's logic here is circular, a fallacy:
[M]arriage is honourable as you say; and if so, wherefore should cuckoldom be a discredit, being derived from so honourable a root?
Fainall starts from the premise that, as Marwood has said, marriage is honorable. He deliberately takes this as a totalizing statement that can never be refuted, no matter what happens in a marriage. Of course, in a world where marriage is increasingly used to move property around and not just to validate a relationship in the eyes of the church, there are many ways to be legally married without honoring all aspects of marriage. But if all marriages are the same and all behavior within a marriage stems from "so honourable a root," getting married absolves people from any responsibility for their bahavior. Fainall can technically remain "honorably" married while cheating on his wife simply because he is married.
Fainall's use of a fallacy is easy to spot and makes him the object of the audience's criticism. Even though his logic technically holds if the initial premise is true, obviously there must be something wrong with that premise if Fainall uses it to come to this conclusion. By leading the audience to criticize this sham use of marriage as a front for bad behavior, Congreve primes them to question other abuses of "manners." For instance, characters are constantly veiling insults in politeness. Fainall's abuse of logic begs the question of why it is so important to be polite, and whether politeness is honorable or whether it is simply bad behavior cloaked in the image of honor.