Class
While the play is not explicitly a tract on class, the theme is central to it. The decisions the characters make and their perspectives on one another, are all largely based on what class they are a part of. Where Tony openly loves low-class people like the drunks in the Three Pigeons, Marlow must hide his love of low-class women from his father and “society.” His dynamic relationship with Kate (and the way he treats her) is defined by who he thinks she is at the time – from high-class Kate to a poor barmaid to a woman from good family but with no fortune. Hastings’ and Marlow’s reaction to Hardcastle is also a great example of the importance of class—they find him impudent and absurd, because they believe him to be of low class, but his behavior would be perfectly reasonable and expected from a member of the upper class, as he truly is.
Money
One of the factors that keeps the play pragmatic even when it veers close to contrivance and sentiment is the unavoidable importance of money. While some of the characters, like Marlow and Hardcastle, are mostly unconcerned with questions of money, there are several characters whose lives are largely defined by a lack of access to it. Constance cannot run away with Hastings because she worries about a life without her inheritance. When Marlow thinks Kate is a poor relation of the Hardcastles, he cannot get himself to propose because of her lack of dowry. And Tony seems to live a life unconcerned with wealth, although the implicit truth is that his dalliances are facilitated by having access to wealth.
Behavior/Appearance
One of the elements Goldsmith most skewers in his play's satirical moments is the aristocratic emphasis on behavior as a gauge of character. Even though we today believe that one's behavior – in terms of “low” versus “high” class behavior – does not necessarily indicate who someone is, many characters in the play are often blinded to a character's behavior because of an assumption. For instance, Marlow and Hastings treat Hardcastle cruelly because they think him the landlord of an inn, and are confused by his behavior, which seems forward. The same behavior would have seemed appropriately high-class if they hadn't been fooled by Tony. Throughout the play, characters (especially Marlow) assume they understand someone's behavior when what truly guides them is their assumption of the other character's class.
Moderation
Throughout the play runs a conflict between the refined attitudes of town and the simple behaviors of the country. The importance of this theme is underscored by the fact that it is the crux of the opening disagreement between Hardcastle and his wife. Where country characters like Hardcastle see town manners as pretentious, town characters like Marlow see country manners as bumpkinish. The best course of action is proposed through Kate, who is praised by Marlow as having a "refined simplicity." Having lived in town, she is able to appreciate the values of both sides of life and can find happiness in appreciating the contradictions that exist between them.
Contradiction
Most characters in the play want others to be simple to understand. This in many ways mirrors the expectations of an audience that Goldsmith wishes to mock. Where his characters are initially presented as comic types, he spends time throughout the play complicating them all by showing their contradictions. Most clear are the contradictions within Marlow, who is both refined and base. The final happy ending comes when the two oldest men – Hardcastle and Sir Charles – decide to accept the contradictions in their children. In a sense, this theme helps to understand Goldsmith's purpose in the play, reminding us that all people are worthy of being mocked because of their silly, base natures, and no one is above reproach.
Comedy
Though it is only explicitly referred to in the prologue, an understanding of Goldsmith's play in context shows his desire to reintroduce his audience to the “laughing comedy” that derived from a long history of comedy that mocks human vice. This type of comedy stands in contrast to the then-popular “sentimental comedy” that praised virtues and reinforced bourgeois mentality. Understanding Goldsmith's love of the former helps to clarify several elements of the play: the low scene in the Three Pigeons; the mockery of baseness in even the most high-bred characters; and the celebration of absurdity as a fact of human life.
Deceit/Trickery
Much of this play's comedy comes from the trickery played by various characters. The most important deceits come from Tony, including his lie about Hardcastle's home and his scheme of driving his mother and Constance around in circles. However, deceit also touches to the center of the play's more major themes. In a sense, the only reason anyone learns anything about their deep assumptions about class and behavior is because they are duped into seeing characters in different ways. This truth is most clear with Marlow and his shifting perspective on Kate, but it also is true for the Hardcastles and Sir Charles, who are able to see the contradictions in others because of what trickery engenders.
