What does Gaskell see as the difference between the working class and upper class?

The primary social theme of the novel, Mary Barton, is the dueling dynamic between the working class and the ruling class. During the 1830s and 1840s, the working classes faced poor working conditions, while the mill and factory owners lived good, decadent lifestyles. The struggles of the workers to achieve some relief from the masters so they can support their families is one of the main themes of the novel. The author primarily focuses on the laborer's point of view and how they are treated by the mill owners, mainly as if they don't really matter.

This class difference is the main trigger for John Barton, who has had enough of being downtrodden and rises up to murder Harry Carson, the mill owner's son. This is devastating to Henry Carson, the mill owner, whose family has risen from the lower classes. One can see his family, mainly his daughters and wife, lounging around with nothing to do, while across the city many more people suffer. When Jem Wilson is wrongly accused of the murder of Harry Carson, he is primarily suspected because of a fight between him and Carson. When a policeman stops the fight, he immediately asks Harry Carson, the richer man, if he wants to press charges, without consulting Jem. This shows how society itself contributed to the oppression of the poor. However, the author believes, at the end of the novel, that conditions will get better, if men like Henry Carson work to make working conditions a concern of the factory owners.