One of the truly greatest philosophers of all time was Plato, a native Athenian born in 427 B.C.  He grew up in a wealthy family and began to appreciate philosophy at some point in his late teens and early twenties, around the time of his introduction to Socrates.  As a student of Socrates, he adopted many of his teacher's beliefs though he certainly had a great mind all of his own.  His early works reflected much admiration for Socrates and since Socrates never wrote any of his own works, Plato's early dialogues are most representative of Socrates' philosophical beliefs.  The format of most Platonic works is called the "dialectic", and was undisputedly mastered by Plato.  His middle dialogues use Socrates as a character advocating Plato's own thoughts, and in his later dialogues Plato is quite critical of himself at an earlier age. 

The middle part of his life was spent philosophizing and writing away from Athens, in a part of Italy inhabited by Greeks.  There, he met other philosophers and scientists who belonged to the "Pythagorean" school of philosophy, and also took up a career in politics.  He eventually founded The Academy, which was a school of higher education offering instruction in mathematics, political studies, and of course, philosophy.  It is believed that Plato spent the rest of his life teaching, researching, and writing at The Academy in the countryside of Athens until he died at the age of eighty-one in 347 B.C.  The famed philosopher Aristotle was one of Plato's students at the Academy, and he remained there for quite some time teaching and writing, up to the time of Plato's death twenty years later.