April 2016 - In the 500s BC, people all over Europe and Asia became more and more interested in great philosophical questions: why are we here? how does the world work? why do things happen the way they do? how can we know for sure? Probably this was related to how people were also experimenting with new forms of government: empires, democracies, republics. In China, the 500s BC saw Confucius and Lao Tzu. In India it was the Buddha. In Babylon, the Jewish prophets Ezra and Nehemiah were writing the Bible, while Zoroastrianism was taking off. In Greece, Thales and Pythagoras tried to impose order on the universe's chaos through the patterns of mathematics and music.
But the three great philosophers who really made ancient Greek philosophy famous lived a little later: Socrates, Plato, and Aristotle. All three of these men lived in Athens for most of their lives, and they knew each other. Socrates came first, and Plato was his student, around 400 BC. The Athenians voted to kill Socrates in 399 BC, and Plato, who was pretty angry about it, began his work by writing down what Socrates had taught, and then continued by writing down his own ideas and opening a school. Aristotle, who was younger, came to Athens as a teenager to study at Plato's school, and ended up starting his own school, the Lyceum, when he grew up.
In the years after Plato and Aristotle died, in the 200s BC, three famous kinds of philosophy started up in the schools that Plato and Aristotle had started. These are the Stoics, the Skeptics, and the Epicureans. Each of these three schools of philosophy continued to be important ways of thinking about the world all the way through the Roman Empire, until people converted to Christianity in the 300s AD, and even after that.
Learn by doing: compare Socrates' dialogues with Taoism
More about Socrates
Philosophy and Science in Ancient Greece: The Pursuit of Knowledge, by Don Nardo (2004). For teenagers. Don Nardo has written many books for young people about the ancient Greeks.
The Cambridge Companion to Greek and Roman Philosophy, edited by David Sedley (1997).