Sophie's World in 10 Minutes: A Philosophy Course Written for a Teenage Girl That Turns Its Readers Into Characters

In Lillesand, a small town on Norway's southern coast, another teenage girl, Hilde Møller Knag, is reading her way through a thick ring-binder manuscript her father mailed home from the UN peacekeeping front in Lebanon. The manuscript is called Sophie's World. Hilde's father, Major Albert Knag, is a UN peacekeeper stationed in Lebanon, and he is also the book's real author - he wrote the manuscript as his daughter's fifteenth-birthday present. One birthday gift, and two girls' summers end up knotted together.

How the Plot Moves

The philosophy course begins at the mailbox. Every time Sophie walks home from school, another letter is waiting - no stamp, no signature, just a question. She answers it, and the next letter tears a hole in her answer and hands her a harder question underneath. From 'Who are you?' to 'Where does the world come from?', from the natural philosophers to Socrates and his claim that the unexamined life is not worth living, Gaarder times the letters to land inside the ordinary rhythm of a teenage summer - one pulled out before bed, one stuffed into a backpack before a camping trip.

Once she has enough questions stacked up, she follows them to the end of the woods and finds the cabin. The door opens, and the man standing inside introduces himself: Alberto Knox. He presses play on an old video recorder, and black-and-white footage flickers onto the screen, light moving over the Acropolis. From this point on, the lessons stop hiding behind paper; the teacher sits across from her in person, with Hermes dozing at his feet. From the pre-Socratics through the Middle Ages, from Descartes to Hume, from Kant's 'Copernican revolution' to Hegel, Marx, and Sartre - Gaarder crams something close to a three-volume history of Western philosophy into one summer.

What's worth noticing in the craft is that the history of philosophy isn't pasted on like encyclopedia entries - it's wrapped around the growing up of one particular girl. What readers remember isn't a parade of philosophers' positions; it's Sophie walking home through the woods at night, clutching a videotape, moonlight coming down through the trees.

The postcards are where the book really starts to turn. One reads 'Happy Birthday, Hilde Knag' and turns up stuck to the inside of a banana peel Sophie has just opened. Another is tucked into Hermes's collar. She runs to ask her mother and Joanna; neither of them has heard the name. The postcards keep turning up in stranger places - every time she opens something that isn't hers, there's a letter inside addressed to someone else.

The truth comes out in the cabin in the woods. Alberto and Sophie piece the clues together: the postcards were written by Major Albert Knag, on peacekeeping duty in Lebanon, and their addressee, Hilde, is his actual daughter, back home in the town of Lillesand. The Major wrote this philosophy novel as her fifteenth-birthday present - which means Sophie herself, and the teacher who has spent a whole summer teaching her philosophy, are both characters invented inside the thick ring-binder manuscript sitting in Hilde's hands.

This is the philosophical heart of the whole book. Sophie has just finished a crash course in existentialism, and she turns around to find that she herself is nothing but a line someone else wrote - 'existence precedes essence' lands on her own life. Shocked and furious in equal measure, she and Alberto work out a plan that is both ridiculous and dead serious: at the garden party Sophie's mother is throwing in her honor, where every fictional character they've encountered along the way is due to show up, they will use the chaos to slip free of the Major's control over the story.