“Sophie’s World” is the story of a young Scandinavian girl named Sophie Amundsen. Out of the blue, mysterious letters begin appearing in her mailbox, inviting her to broaden her mind and start studying philosophy. Her “correspondence course” begins with the early Greek philosophers and then moves through the course of human history, discussing the Middle Ages, the Baroque period, the Romanticists, the Enlightenment movement, and much more. Sophie also finds that she is receiving letters addressed to a mysterious girl named Hilde, whose father is apparently serving in Lebanon with the United Nations. A large part of the tension in the early part of the story revolves around the identity of the mysterious philosopher sending her these letters.
Eventually, it becomes clear that she is learning from a man named Albert Knox, a reclusive philosopher whose goal is to give her a different outlook on the world. But Knox isn’t the one who has been sending her the letters addressed to Hilde. Together, they try to understand the significance of these strange, seemingly interconnected letters – even as the world around them seemingly becomes more and more surreal. Odd things begin to happen – a message is found written in ink on the inside of an unpeeled banana. Sophie passes by a dog who says “Happy birthday, Hilde!” A sea serpent appears in a formerly tranquil lake.