Plato

Born into an aristocratic family with forefathers such as kings of Athens and Solon, Plato was born in Athens. His mother Perictione remarried Pericles' associate Pyrilampes when his father Ariston died.
A disciple of Socrates, eventually witnessing the philosopher's execution in 399BC, he feared for his safety and went travelling to Italy and Egypt. He returned to Athens after his travels and founded the first European university, the Academy. There, astronomy, biology, mathematics, politics and philosophy was taught, with Aristotle as the most famous student.

After a failed effort to make Dionysius the Younger of Sicily a philosophical ruler Plato spent the rest of his life teaching and writing at the Academy. He wrote dialogues, putting words in the mouths of historical people like his teacher Socrates. Because of this, it is sometimes difficult to know which texts express Platos' thoughts and which express the thoughts of others. Therefore, his works are usually divided in three kinds of dialogues: Where Socrates thoughts are expressed, where Socrates is used to express Platos' thoughts, and the ones where Plato himself seaks.
Of his many works, some the most famous dialogues are Protagoras (on the structures of the virtues), The Republic (on justice), Apology (Socrates defence speech), Phaedo (the death of Socrates), Timaeus (on the principles of the cosmos), Symposium (on love), The Republic (on the nature of justice in the soul and the state) and The Laws (on the laws that an mediate between human irrationality and rational knowledge).
One of Platos most famous stories is the one of Atlantis, which according to him was situated west of the Pillars of Heracles (Gibraltar), and consisted of a mighty people of great virtue. This ideal state was destroyed when the people was corrupted.
It was Plato who invented the concept of Hell. In his dialogue Gorgias he speaks of the eternal punishments, a thought later adopted by the Christians.
Plato was much influenced by his teacher Socrates, and often used him as a character in his dialogues, but he wanted to take the nature of knowledge a step further. Through reason one can achieve knowledge, and his most famous example is the one he uses in The republic, where he compares humanity and its perceptions with people sitting in a cave with their backs towards the entrance. They see shadows on the cave's wall, but do not realise that the actual objects are outside the cave and the shadows only their reflections.
He also compared the state and the individual, stating they both consisted of three parts: the desiring, the spirited and the rational. If they are all in harmony but ruled by the rational you have justice. Therefore, he concluded, the two lower classes must be ruled by the upper class, according to Plato the philosophers, for the society to be correct. Class has to do with education, and not with birth or sex, starting with music and gymnastics and ending with mathematics. When a person qualifies as a philosopher of the upper class, he must be deprived of private property and pay attention to civic affairs.

"Until philosophers are kings...cities will never cease from ill, nor the human race." Plato