What is the meaning of life for Despereaux?
I believe the meaning of life for Despereaux can be summarized in a phrase he says often to the Princess Pea: "I honor you." His whole goal in life is to honor, as a courtly knight to his fair maiden, the Princess Pea, whom he loves. He soon realizes, when he hears of Roscuro's evil plan and then sleeps through her kidnapping, that honor sometimes means sacrifice. He must do the one thing that he was most fearful to do: go back into the dungeon and trust an evil rat to lead him to his princess. He has to muster all his courage and strength to do this, for he quickly learns upon finding the princess that he must fight Roscuro for her freedom. In the end, he shows the most honor, not by marrying her, but by being her friend and having many more adventures with her. Despereaux's life of sacrificial love for the princess shows us that honoring others might cost us dearly, but the price is well worth it.
Furthermore, although the book mostly focuses on Despereaux's honor for the princess, I believe he also shows a different type of sacrificial honor for those in his family. For example, although his father chooses to turn him in for revealing himself to a human, throughout the story, Despereaux refuses to be bitter or take revenge against his father. He knows that in order to save his own heart, he must forgive his father completely. Also, he is hurt by how his siblings treat him, namely when his own brother Furlough leads him to the dungeon, but does not treat them with unkindness either. He has every right to be bitter towards his family who committed "perfidy" against him, but in the end, they all know that he honors them by showing forgiveness. Throughout the whole book, although many times Despereaux is treated terribly, he always chooses to take the higher road and honors others by showing forgiveness. This is why I believe Despereaux's meaning of life is to show honor to everyone, no matter how they treat him.