The Preface makes clear that while Fielding's outlook is undoubtedly comic, his comic writing nevertheless has a serious point. Fielding rejects the genre of conventional romance because it contains "very little instruction or entertainment," whereas Fielding's twofold goal is precisely to instruct and entertain. The notion that good art is "utile et dulce," both useful and sweet, educational and enjoyable, comes from the Roman poet Horace, an authoritative source of classical thinking on the purposes of art. Fielding makes ironic reference to Horace in Chapter I when, having listed a number of popular tales available in cheap pamphlet form, he remarks, "In all these, Delight is mixed with Instruction, and the Reader is almost as much improved as entertained." The target of his irony here is not the classical principle itself but the modern works that fail to live up to that principle. In outlining his own "utile et dulce" approach to the novel, Fielding rejects burlesque and caricature because he wants to inspire laughter not for its own sake but constructively, with humor being the vehicle of moral commentary. His target, therefore, will not be "what is monstrous and unnatural," what never really occurs in life and thus, in being exposed, cannot edify readers; rather, he will "confine [himself] strictly to Nature," exposing "the true Ridiculous" as it exists in everyday life, thereby performing a corrective function for the morals of the age.

In Fielding's analysis, the outstanding moral fault of the day -- the fault which is consequently the outstanding preoccupation of Fielding's writing -- is "Affectation," the "only source of the true Ridiculous." Affectation comes in two forms: the Affectation that arises from Vanity and the Affectation that arises from Hypocrisy. Fielding treats the latter as the more dangerous flaw, because when hypocrites conceal their true motives and attitudes, they may deceive other people, sometimes to very serious effect. Fielding seeks to oppose the forces of affectation by making vain and hypocritical people seem ridiculous, and he executes this project by employing a kind of humor that encourages solidarity among readers, who are implicitly assumed to be on Fielding's side. In inspiring readers to laugh at affected people, Fielding insinuates that society breaks down into two camps, the affected and the genuine, and his moralizing humor supplies readers with incentives, mainly a string of jokes and a sense of moral superiority, to join (or remain on) the side of the genuine. This literary program effectively exempts readers from Fielding's criticism, and one may validly object to it on the grounds that it actually encourages moral complacency on the part of readers, allowing them to feel that they confirm their own righteousness simply by laughing at others. Ironically, this sort of moral laziness would itself be a form of affectation.

Fielding soon presents two paragons of hypocrisy in Lady Booby and her servant and imitator Mrs. Slipslop. Lady Booby dissembles her motives continually, for example in walking out with Joseph: supposedly, she sees “the Effects which Town-Air hath on the soberest Constitutions,” so she heads to Hyde Park with her handsome footman, whose arm she will naturally require as support. More serious is her conduct following the death of her husband. Fielding’s manner of announcing Sir Thomas’s death is immensely clever: “At this Time, an Accident happened which put a stop to these agreeable Walks, . . . and this was no other than the death of Sir Thomas Booby, who departing this Life, left his disconsolate Lady confined to her House.” By killing off Sir Thomas in a subordinate clause, Fielding insinuates that Sir Thomas’s living or dying is of merely secondary importance to his own wife, who considers his departure from this life only in terms of its effects on her, since it compels her to stay indoors for a period of ritual mourning. Thus, the reader understands “disconsolate” in a sarcastic sense even before learning that Lady Booby’s visitors consoled the bereaved widow with card games and before witnessing the ease with which she rebounds and attempts to acquire a new bed-mate.

Mrs. Sliplsop takes after her mistress both in her passion for Joseph and in her attempts to appear other than she is. In a helpfully literal moment in Chapter III, Fielding shows the simple and trusting Mr. Adams unable to understand the pretentious Slipslop, that "mighty Affecter of hard Words"; in a parallel moment in Chapter V, Joseph fails to understand the sexual suggestions of Lady Booby. Both Mr. Adams and Joseph are too trusting and deferential to react properly to the tortured relationships between appearance and reality: the learned Adams recognizes Slipslop's coinages as solecisms, but his ingenuous respect for her gentility abashes him into complicity with her pretensions; similarly, Joseph has seen enough of the world (or at least of London) that the evidences of Lady Booby's libido are not totally baffling to him, and yet his reverence for her exalted status causes him to lose the thread: “if it had not been so great a Lady, I should have thought she had had a mind to me.” Both Lady Booby and Sliplsop have a mind to him, of course, and Fielding clearly intends their rivalry to be the source of much humor: the incongruity of so much sexual vigor animating Slipslop’s homely postmenopausal body is, in Fielding's view, not only funny in itself but funny in relation to the passion of Lady Booby. The fact is that Lady Booby, though possessing so many seeming advantages (of status, comparative youth, and presumably beauty) over her waiting-gentlewoman, in fact has no better chance with the footman.

The character of Joseph has been a stumbling-block to many modern readers for whom sexual purity may not seem intrinsically valuable, and the extent to which Fielding intended even eighteenth-century readers to take his title character seriously is a matter for debate. The character of Joseph has a serious precedent in the Book of Genesis, in which his namesake is sold as a slave to the house of Potiphar and rebuffs heroically the sexual advances of Potiphar's wife; Joseph also, however, has a precedent in contemporary English literature, namely Samuel Richardson's Pamela Andrews, whom Fielding has made into Joseph's sister and idol. Fielding detested Richardson's novel and its heroine, so that insofar as Joseph functions as a stand-in for Richardson's Pamela, Fielding almost certainly intended him and his virtue to be risible. As Maurice Johnson comments, there is undeniably something absurd about "a squeamish male Pamela, strong, handsome, and twenty-one," and yet the actual humor value of Joseph's defense of his virtue tends to arise mostly from the miscalculations and psychological turmoil of Lady Booby and the low comedy of the vulgar Slipslop. As the story moves away from the voracious London ladies to follow Joseph on his quest for home, Joseph's virtue will seem less absurd, in part because Joseph will have less cause to be squeamish. Crucially, however, what will become apparent is that Joseph's virtue, unlike that of Lady Booby, is in no way affected: he is motivated not by a desire to appear virtuous to others but by a determination to remain loyal to his beloved Fanny Goodwill.