Sophie receives two mysterious letters at her house, asking her "Who are you?" and "Where does the world come from?". The letter is addressed to Hilde Knag c/o Sophie. These questions make Sophie ponder about life, and thus she begins her long philosophical journey.
For the following weeks Sophie begins to receive letters about the history of philosophy anonymously. Soon, her correspondent reveals himself as Alberto Knox. Throughout her philosophy course, Sophie learns about the classic Greek philosophers such as Socrates and Plato, all the way to Karl Marx and Sigmund Freud.
Eventually, the narration switches to Hilde Knag. It is revealed that her father, Albert Knag, is an author who created Sophie and Alberto. Alberto and Sophie speed through a plethora of philosophers, and as the novel progresses Sophie begins to understand more of life and her world.
At a garden party near the end of the book, Albeto and Sophie disappear from the world after learning that they are a figment of Albert Knag's mind. Albert Knag is coming to visit Hilde, and Sophie and Alberto drive to meet Hilde at Lillesand. During Sophie and Alberto's journey, they realize they can go through everything and that no one can hear them; they are essentially spirits from books. They eventually meet Hilde and Albert, but they cannot interact with each other. However, Sophie manages to elicit a small response after hitting Hilde in the head with a wrench. Sophie thus begins learning how to interfere in the world of Hilde and Albert.
Throughout the story, Sophie learns about several different figures in philosophy. Following is a list of some:
|Heraclitus/Parmenides||Heraclitus: Everything is in a constant state flux. Change is the basic principle. The world is characterized by opposites.
Parmenides: Nothing can change; sensory perception is unreliable.
|Empedocles||Nothing changes. Basic elements: Earth, Fire, Water, Air. All matter is constituted by these.|
|Anaxagoras/Democritus||Anaxogoras: All matter made of tiny particles called atoms.
Democritus: Came after Anaxagoras. Believed atoms were uncuttable, and there is an infinite amount of atoms.
|Socrates||"Gadfly of Athens". Questioned people about everything.|
|Thomas Aquinas||God exists due to reason and faith. God is evidence of Final Cause - Christianized Aristotle.|
|Rene Descartes||Rationalist, believed reason is the path to knowledge. Cogito ergo sum" ("I think therefore I am").|
|Baruch Spinoza||Rejected Bible, thought it as product of humans in history. Jesus revolutionary, religions should value love. Laws of God governed humans. Rejected by Jews and Christians, and disowned by family.|
|John Locke||Tabula rasa, blank slate. Man's mind starts clean, and experience creates the mind. Empiricist - those who believed mind consists of things observed by senses.|
|George Berkeley||Since we exist in the mind of God, all thought has cause beyond experience under God. No other perspective for reality.|
|David Hume||Daily experience forms basic ideas, accumulating into complex ideas. For example, basic ideas of human + wings = angels. We can conceive of things like angels, but not experience them. Impressions are experiences at the moment, and ideas are reflections of those impressions.|
|Hegel||History is like rivers: There is one truth, but then another idea comes into conflict with this truth, and they merge into another truth. This is called thesis, antithesis, and synthesis. A thesis and antithesis lead to synthesis.
Believed all knowledge is human knowledge, no fixed, eternal truths. No truth above human reason.
|Kierkegaard||Existence defined by actions and action based on faith. One cannot know objectively that one must believe in faith.
Three stages in life: aesthetic, ethical, and religious stages. Aesthetic is living for enjoyment. This will lead to eventual angst and hopelessness, called existential situation. The person will have to make their own choice - moral or immoral - until they eventually reach the highest stage --the religious stage.
|Friedrich Nietzsche||Sought for revaluation of everything. Physical world only exists, ignore supernatural ideas. "God is dead".|
|Sartre||Man must create values or else he will feel useless. Existence greater than actions, man is responsible for creating himself and being responsible for everything done. Individual creates meaning in meaningless world.|
|Charles Darwin||Sailed on HMS Beagle to observe nature. Scientific works contradict Bible teachings on creation. Every species had been created separately, not from God. Evolution: species adapt and the strongest survive to this day.|
|Sigmund Freud||Human psychology consists of id, ego, and superego. Id is the creative force that urges people to fulfill survival instincts and pleasure. Ego is the person's link to reality. Superego informs people of morally unacceptable behavior, and people repress these actions.
Theories on the unconscious. Man is always under attack from irrational impulses; humans always have to repress these urges to remain in society.