Sophie is the main character in Sophie's World. She is the creation of Albert Knag in order to amuse his daughter Hilde. Along with Alberto Knox, Sophie is a part of Hilde's birthday present. Sophie is to turn fifteen on June 15, the same day as Hilde. Sophie is clearly created as somewhat of a counterpart to Hilde, but she and Alberto manage to escape Albert Knag's mind and gain an existence of their own. Throughout the book Sophie learns how to be a philosopher. Early on she ponders the questions that Alberto gives her and has good thoughts about them but she really does not know how to answer them. However, as the lessons continue Sophie's mind becomes extremely acute. She remembers everything that Alberto has taught her because it is all- important to her and she is able to come up with interesting philosophical propositions of her own. Although Alberto knows more about philosophy than Sophie does, she fares better when they enter their new lives as beings of spirit existing within Hilde's world. Perhaps this is because Alberto has trained Sophie and so she has not only picked up what he has tried to teach her but also been critical of him. She was given the best education possible and uses it to the best of her abilities. Sophie figures out that she and Alberto can have an effect on Hilde's world when she dares to think that they can. Alberto disagrees with her, but Sophie has learned from him that the opinions of others should not have the power to dissuade someone from an action they believe in. Sophie is also extremely individualistic. She learns from Alberto but she thinks on her own. She is critical of him, her mother, and her friend Joanna. Sophie acts with conviction and thinks things through before she does them and that makes it difficult to fault her. After all, she is only a fifteen year old girl, and she acts extremely mature for her age.