What is a main theme?

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.