Plato is one of the world's best known and most widely read and studied philosophers. He was the student of Socrates and the teacher of Aristotle, and he wrote in the middle of the fourth century B.C.E. in ancient Greece. Though influenced primarily by Socrates, to the extent that Socrates is usually the main character in many of Plato's writings, he was also influenced by Heraclitus, Parmenides, and the Pythagoreans.
There are varying degrees of controversy over which of Plato's works are authentic, and in what order they were written, due to their antiquity and the manner of their preservation through time. Nonetheless, his earliest works are generally regarded as the most reliable of the ancient sources on Socrates, and the character Socrates that we know through these writings is considered to be one of the greatest of the ancient philosophers.
Plato's middle to later works, including his most famous work, the Republic, are generally regarded as providing Plato's own philosophy, where the main character in effect speaks for Plato himself. These works blend ethics, political philosophy, moral psychology, epistemology, and metaphysics into an interconnected and systematic philosophy. It is most of all from Plato that we get the theory of Forms, according to which the world we know through the senses is only an imitation of the pure, eternal, and unchanging world of the Forms. Plato's works also contain the origins of the familiar complaint that the arts work by inflaming the passions, and are mere illusions. We also are introduced to the ideal of "Platonic love:"Plato saw love as motivated by a longing for the highest Form of beauty—The Beautiful Itself, and love as the motivational power through which the highest of achievements are possible. Because they tended to distract us into accepting less than our highest potentials, however, Plato mistrusted and generally advised against physical expressions of love.