Answer: Socrates, Plato and Aristotle
The three great philosophers that appeared back-to-back in Greek civilization were Socrates, Plato and Aristotle.
Socrates was a philosopher in Ancient Athens who was convicted of corrupting the youth and punished by death. He used the famous Socratic method of teaching.
Plato was a student of Socrates, known for his famous treatise The Republic. Aristotle, in turn, was Plato's student (and also tutor of Alexander the Great, the Macedonian king).