At several points in the novel, the narrator claims that the whole thrust of the book is from social evil to social good, proving that progress, while slow and complex, is inevitable. One way this movement is symbolized is through the progression from darkness into light. Darkness symbolizes the various kinds of evil that are enacted, consciously or unconsciously, in society: the abandonment of children, the despicable treatment of women, and the lack of mercy shown to those who have broken society’s rules (like convicts). Light, on the other hand, comes to stand for knowledge, truth, mercy, and goodness—those who have “seen the light” no longer blindly follow society’s judgmental assertions and assumptions.
The narrator often uses the language of light and darkness to imply this progress from social backwardness into a progressive society. But light and darkness, in turn, also fill the scenes of the novel, allowing the reader to associate certain characters and places with evil or with good. The members of the Patron-Minette criminal gang in Paris, for instance, only ever go out at night, in the darkness, while the Bishop of D— is often described as lit up in his very demeanor. Other characters pass through darkness on their way to the light. Cosette’s moment of greatest despair comes as she wanders through the black forest at night to fetch water for the Thenardiers, while Valjean’s greatest challenge is to carry Marius, whom he hates for taking Cosette away from him, through the ominous, gloomy, underground sewers of Paris. This journey from darkness to light, however, is considered necessary—the only way to achieve mercy and goodness.