Plato was one of the most important classical Greek philosophers. He lived from 427 BC to 348 BC. A wealthy man, he owned at least 50 slaves and created the first university school, called "The Academy". Plato was a student of Socrates (who did not write) and the teacher of Aristotle, who founded another university, known as the Lyceum. Plato wrote about many ideas in philosophy that are still talked about today. He wrote about ideas of deductive reasoning. One modern philosopher, Alfred North Whitehead, said that all philosophy since Plato has just been comments on his works.