The novel is primarily concerned with the theme of revolution and social strife. Hugo was profoundly concerned by the class differences that set the 1789 French Revolution in motion. Discord between the Clergy, Nobility, and the Third Estate (a middle class of artisans, craftsmen, and intellectuals) toppled the monarchy and established a republican government that no longer recognized the special privileges of the aristocracy and the Church.
Writing during the July 1830 Revolution, Hugo was more conscious of class divisions than ever. For example, as the vagabonds prepare to march, Clopin declares: "Trade is incompatible with nobility." Consequently, the vagabonds' assault on Notre Dame represents an example of historical foreshadowing that would remind Hugo's contemporary readers of the 1789 storming of the Bastille. The fact that Louis XI is in the Bastille when the vagabonds attack further emphasizes this historical reference. The fact that every character is an orphan also evokes the deterioration of the feudal system. French society was viewed as one giant happy family under the Bourbon kings and the breakdown of this family unit in the novel foreshadows the civil wars that would divide the nation in two beginning in 1789.