Plato was the first person to organize and record the issues and questions that define philosophy. As Socrates' student, Plato preserved the teachings of his great mentor in many famous "dialogues"; these deal with classic issues like law and justice, perception and reality, death and the soul, mind and body, reason and passion, and the nature of love. The dialogues also discuss the value of moral principle vs. the value of life itself; how to achieve virtue; and how each of us can fulfill our true nature.

The most famous of all Platonic doctrines is the "theory of forms." This theory that any object's true reality is found in its rational form or structure rather than in its material appearance. And Plato's Republic presents his distinctive (and much criticized) vision of the ideal state.

Plato believed that philosophy begins in the sense of wonder. With Socrates, he sees philosophy as reason, unhindered by feelings, emotions, and the senses. And from these two great thinkers we have received perhaps the most well known of all philosophical utterances: "the unexamined life is not worth living."