This is an interesting question, and it assumes that Dickens had only one motive in writing A Tale of Two Cities--to satirize the French Revolution. His primary motivation was undoubtedly money, as he was famously always in need and got paid by the word (which explains, in part, the length of all his works). More significantly, though, this novel is written as a cautionary tale. The famous opening paragraph sets up a parallel between England and France, places where monarchs reign and the people are deprived. As the story progresses, this parallel continues. In fact, in this story of justice and judgment, the first trial we read about happens not in France but in England, a place where people are sentenced to death these days for minor infractions and misdeeds. Unrest is certainly at a full boil in France; however, in England the heat is on and a slow simmer has begun. The story is a warning to is countrymen about an irrational response to an oppressive regime (the king plus the aristocrats). Dickens recognizes that his country is not far from the same kind of violent mutiny which broke out in France and uses his story as a warning. The purpose of satire is to ridicule in order to make better or change; in this case, what he is hoping to do is avert an English Revolution.