Virtue as action rather than thought
Fielding contrasts the concept of Virtue espoused by characters like Square and Thwackum with the Virtue actually practiced by Jones and Allworthy. Tom, as the active hero who saves damsels-in-distress and plans on fighting for his country, is the embodiment of the very active type of Virtue that Fielding esteems.
The impossibility of stereotypical categorization
Fielding's novel attempts to break down numerous boundaries. In terms of genre, Fielding cannot decide whether his novel is a "philosophical History," a "Romance," or an "epi-comic prosaic poem." Yet, through these confounded musings, Fielding subtly suggests that cataloguing fiction is silly, and that he would rather think of himself as "the founder of a new Province of Writing."
In another example of broken stereotypes, Fielding's characters cannot be distinguished by "masculine" or "feminine" traits: in this novel both men and women fight and cry.
The tension between Art and Artifice
Although the narrator upholds the value of natural art in his characters, he uses artifice himself in the construction of his novel. For example, he often closes chapters by hinting to the reader what is to follow in the next chapter, or he warns the reader that he is going to omit a scene. In such a way, he prevents us from suspending our disbelief and giving ourselves up to the "art" of the narrative—instead, Fielding constantly entices us to reflect on and review the process of construction.