How we cite our quotes: (Book.Chapter.Paragraph)
Quote #4
Though Mr Blifil was not of the complexion of Jones, nor ready to eat every woman he saw; yet he was far from being destitute of that appetite which is said to be the common property of all animals. […] Now the agonies which affected the mind of Sophia, rather augmented than impaired her beauty; for her tears added brightness to her eyes, and her breasts rose higher with her sighs. Indeed, no one hath seen beauty in its highest lustre who hath never seen it in distress. Blifil therefore looked on this human ortolan with greater desire than when he viewed her last; nor was his desire at all lessened by the aversion which he discovered in her to himself. On the contrary, this served rather to heighten the pleasure he proposed in rifling her charms, as it added triumph to lust. (7.6.12)
When Tom first thinks of sleeping with Molly, he worries a lot about her reputation and her innocence. Tom has a lot of lust in his character—as this passage says, he is "ready to eat every woman he saw." But Tom's desire depends on the consent of his partner, which clearly makes a huge moral difference. Mr. Blifil wants Sophia because she doesn't want him, which obviously makes him the complete ethical opposite of Tom. Where a lot of people might condemn Tom for giving in to his lusts all the time (and it does get him into a lot of trouble), the narrator is saying, hey, hold up—the problem isn't lust itself. It's the kind of lust. Mr. Blifil's desire to hurt Sophia is morally wrong, where Tom's sexuality is just kind of undisciplined.
Quote #5
Now it required no very blameable degree of suspicion to imagine that Mr Jones and his ragged companion had certain purposes in their intention, which, though tolerated in some Christian countries, connived at in others, and practised in all, are however as expressly forbidden as murder, or any other horrid vice, by that religion which is universally believed in those countries. The landlady, therefore, had no sooner received an intimation of the entrance of the above-said persons than she began to meditate the most expeditious means for their expulsion. (9.3.6)
This passage is kind of ambiguous, but it also appears pretty critical of laws and customs that label sexuality as bad. We say that it's ambiguous because it's unclear if the "certain purposes" the narrator mentions here mean sex in general (outside of a marriage and not for reproduction) or something more specific, such as prostitution. Whichever it is, the narrator points out that you can find people having sex in every country, no matter how much of a "vice" it is supposed to be. The narrator points out that Tom and Mrs. Waters's activities are "practised in all" Christian countries. What is the point of declaring something "as expressly forbidden as murder" when it continues to happen all the time, everywhere? Isn't that just an invitation to hypocrisy and deception?
Quote #6
"La, madam," cries Honour, "you will make a very bad examiner. Hark'ee, child," says she, "is not that very young gentleman now in bed with some nasty trull or other?" Here Susan smiled, and was silent. "Answer the question, child," says Sophia, "and here's a guinea for you."—"A guinea! madam," cries Susan; "la, what's a guinea? If my mistress should know it I shall certainly lose my place that very instant." "Here's another for you," says Sophia, "and I promise you faithfully your mistress shall never know it." Susan, after a very short hesitation, took the money, and told the whole story, concluding with saying, "If you have any great curiosity, madam, I can steal softly into his room, and see whether he be in his own bed or no." She accordingly did this by Sophia's desire, and returned with an answer in the negative. (10.5.6)
The main problem with Tom's sleeping around is that he almost ruins his relationship with Sophia, the woman he claims he loves. So it seems like Fielding is arguing that the difficulty with totally giving in to your physical desires isn't what it does to "society" or abstract ideas like that. The issue is that, by being unfaithful, you can hurt the person you love (especially if that person expects you not to sleep around). And the one who ultimately almost pays for his lustfulness is Tom himself. After all, if Susan hadn't spotted him with Mrs. Waters at the inn at Upton, his issues with Sophia might have been resolved right then and there.