Plato lived from c. 428 to c. 348 BC, and founded the Western world’s first school of higher education, the Academy of Athens. Almost all of Western philosophy can be traced back to Plato, who was taught by Socrates, and preserved through his own writings, some of Socrates’s ideas. If Socrates wrote anything down, it has not survived directly.

Plato and Xenophon, another of his students, recounted a lot of his teachings, as did the playwright Aristophanes. Plato was an opponent of the relativism and scepticism of the Sophists; but, like them he focused on values rather than on physical science. Aristotle credits Socrates with emphasizing moral questions and precise definitions; and Plato surely absorbed these lessons.

One of Plato’s most famous quotations concerns politics, “Until philosophers rule as kings or those who are now called kings and leading men genuinely and adequately philosophize, that is, until political power and philosophy entirely coincide, while the many natures who at present pursue either one exclusively are forcibly prevented from doing so, cities will have no rest from evils…nor, I think, will the human race.” What he means is that any person(s) in control of a nation or city or city-state must be wise, and that if they are not, then they are ineffectual rulers. 

It is only through philosophy that the world can be free of evils. Plato’s preferred government was one of benevolent aristrocrats, those born of nobility, who are well educated and good, who help the common people to live better lives. He argued against democracy proper, rule by the people themselves, since in his view, a democracy had murdered his teacher, Socrates.

Although they continue to use the talkative Socrates as a fictional character, the middle dialogues of Plato develop, express, and defend his own, more firmly established, conclusions about central philosophical issues. Beginning with the Menwn (Meno), for example, Plato not only reports the Socratic notion that no one knowingly does wrong, but also introduces the doctrine of recollection in an attempt to discover whether or not virtue can be taught. The Faidwn (Phaedo) continues development of Platonic notions by presenting the doctrine of the Forms in support of a series of arguments that claim to demonstrate the immortality of the human soul.

Plato’s most enduring theory, if not his political theories, is that of “The Forms.” Plato wrote about these forms throughout many of his works, and asserted, by means of them, that immaterial abstractions possess the highest, most fundamental kind of reality. All things of the material world can change, and our perception of them also, which means that the reality of the material world is weaker, less defined than that of the immaterial abstractions. 

Plato argued that something must have created the Universe. Whatever it is, the Universe is its offspring, and we, living on Earth, our bodies and everything that we see and hear and touch around us, are less real than the creator of the Universe, and the Universe itself. This is a foundation on which #4 based his understanding of existentialism.

In 367 BC Dionysius died and was succeeded by his teenage son, Dionysius II, whose uncle, Dion, was a close friend to Plato. Dion invited Plato to come a school Dionysius for his future kingship. Plato, seeing that this was a way for him to complete his goal for a philosopher king decided to travel to Sicily and take control of the boy's studies. Dionysius II later had a fight with Dion, and exiled him, Plato was unable to convert the boy to philosophy and returned the Athens, where Dion had established residence. 

Plato continued correspondence with Dionysius II, and tried to have him reconcile with Dion. Dionysius II lured Plato into a trap, by telling him that he wanted to become a philosopher. Plato was trapped in Syracuse until 360. Where he traveled back to Athens and continued to function as president of the Academy. 

He died in 347 BC, at about the age of eighty.