All the major themes in The Tale of Despereaux exist under the overarching umbrella of the struggle between light and dark. Throughout the novel, light, representing all that is good and supports life—love, hope, forgiveness, the power of storytelling, kindness, and empathy—is constantly threatened by darkness, representing all that is evil and destroys life—despair, suffering, treachery, betrayal, revenge and closed-mindedness. Literally, light and dark are represented by the two worlds in which the story takes place: the upstairs of the castle, where light streams through the windows, and the dungeon, where eternal darkness reigns. Throughout the novel, characters are forced into the dungeon because of other’s evil intentions: the mice banish Despereaux to the dungeon, and later, Roscuro kidnaps Pea and takes her to the dungeon. On the other hand, characters strive to escape from the dungeon, to reach the world of light, life and hope. Roscuro, whose full name is Chiaroscuro, a word describing the contrast between light and darkness, is obsessed with light even though he lives in the dark. He tries to escape to the world of light upstairs, but he is forced back into the dungeon, where he allows the darkness to corrupt him until all he thinks of is revenge. Despereaux also escapes the dungeon; however, he returns to the dark of his own volition in order to rescue Pea. With this turn of events, the author suggests that it is not enough to run from the darkness: one must confront the dark aspects of the world, and of one’s own self, in order to truly overcome them.

Throughout The Tale of Despereaux, forgiveness provides a way for characters to find light and save themselves; those who cannot forgive find themselves stuck in the darkness. Instead of forgiving Pea for her harsh words after her mother’s death, Roscuro lets his hate and anger stew into a powerful desire for revenge. As a result, his heart mends in a “crooked” way, and even when he is granted access to the light upstairs, he finds he can never truly belong or be happy in either the light or the darkness.

Pea, on the other hand, does forgive Roscuro, and in so doing confronts and overcomes the dark parts within herself. Looking inside her heart, the princess finds a “burning coal of hatred” for the rat who caused her mother’s death. At the end of the novel, when Despereaux is about to kill Roscuro, Pea suddenly realizes how “fragile” her heart is, as the darkness within it is always fighting against the light. The princess realizes that, “to save her own heart,” to keep the darkness within from conquering, she must forgive the rat and spare his life.
Despereaux makes a similar discovery when his own father begs him for forgiveness. Even though his father betrayed him and left him to die in the dungeon, Despereaux forgives him, for he realizes doing so is the only way to stop his heart “from breaking in two.”

The danger of blind conformity is one of the many aspects of darkness explored throughout the novel. Despereaux is considered a threat and eventually sentenced to death merely because he doesn’t act like the other mice. Roscuro, too, is alienated from the other rats by his attraction to light. And the king, refusing to give up his belief that all rodents are liars, misses a chance to save his beloved daughter.

Despereaux, on the other hand, is a shining example of nonconformity. As the author tells us, “an interesting fate awaits almost everyone, mouse or man,...