As well as being a great story, Dom Casmurro also gives us a very useful insight into the social and political changes then taking place in Brazil. During the nineteenth century, when the story is set, Brazil was slowly beginning the transition to modernity, a process facilitated by growing prosperity and urbanization.

Although Brazilian society remained quite hierarchical on the whole, the rise of the middle-classes ensured that it became much more open than ever before. As middle-class values gradually became more prominent, the institution of slavery, a lynchpin of the Brazilian socio-economic system for centuries, came increasingly under threat.

With slavery becoming less socially acceptable, well-to-do families like Bento Santiago's employed agregados instead of slaves. An agregado was a kind of unpaid servant who worked in return for the granting of favors by the family of which he was a dependent. In Dom Casmurro, the character of Jose Dias is an agregado, working in various capacities for Bento Santiago's family.

As well as being the family doctor, Jose Dias also acts as a kind of unofficial spiritual adviser. He advises Bento's widowed mother Dona Gloria to place her son in a seminary to nip his burgeoning romance with the young girl next door in the bud. Jose also encourages Dona Gloria against her own inclinations to let Bento attend the theater, as he believes it will act as a school of manners for him.

Jose Dias could be said to represent the kind of middle-class values that were becoming increasingly prominent in Brazilian society and were slowly but surely setting the stage for the more thoroughgoing social and political changes that would take place in the 1890s, the decade in which Dom Casmurro was written.