Sophie's world: a novel about the history of philo (Roman)

Wanting to understand the most fundamental questions of the universe isn't the province of ivory-tower intellectuals alone, as this book's enormous popularity has demonstrated. A young girl, Sophie, becomes embroiled in a discussion of philosophy with a faceless correspondent. At the same time, she must unravel a mystery involving another young girl, Hilde, by using everything she's learning. The truth is far more complicated than she could ever have imagined.