Greek philosopher (c. 427 – 348 BC)
Plato ( ; Greek: Πλάτων, "Plátōn", born c. 428-423 BC, died 348 BC) was an ancient Greek philosopher of the Classical period who is considered a foundational thinker in Western philosophy and an innovator of the written dialogue and dialectic forms. He influenced all the major areas of theoretical philosophy and practical philosophy, and was the founder of the Platonic Academy, a philosophical school in Athens where Plato taught the doctrines that would later become known as Platonism. 
Plato's most famous contribution is the theory of forms (or ideas), which aims to solve what is now known as the problem of universals. He was influenced by the pre-Socratic thinkers Pythagoras, Heraclitus, and Parmenides, although much of what is known about them is derived from Plato himself.
Along with his teacher Socrates, and his student Aristotle, Plato is a central figure in the history of Western philosophy. Plato's complete works are believed to have survived for over 2,400 years—unlike that of nearly all of his contemporaries. Although their popularity has fluctuated, they have consistently been read and studied through the ages. Through Neoplatonism, he also influenced both Christian and Islamic philosophy. In modern times, Alfred North Whitehead said: "the safest general characterization of the European philosophical tradition is that it consists of a series of footnotes to Plato."
Name.
There is a traditional story that 
Plato is a nickname. According to Diogenes Laërtius, writing hundreds of years after Plato's death, his birth name was "Aristocles" (), meaning 'best reputation'. "Plátōn" () sounds like "Platus" or "Platos", meaning "broad", and according to Diogenes' sources, Plato gained his nickname either from his wrestling coach, Ariston of Argos, who dubbed him "broad" on account of his chest and shoulders, or he gained it from the breadth of his eloquence, or his wide forehead. Philodemus, in extracts from the Herculaneum papyri, corroborates the claim that Plato was named for his "broad forehead". Seneca the Younger, writing hundreds of years after Plato's death, writes "His very name was given him because of his broad chest."
According to the traditional story, Plato was originally named after his paternal grandfather, supposedly called Aristocles; the name "Plato" was only used as a nickname; and the philosopher could not have been named "Plato" because that name does not occur previously in his family line.
Modern scholarship tends to reject the "Aristocles" story. Plato always called himself "Platon". "Platon" was a fairly common name (31 instances are known from Athens alone), including people named before Plato was born. Robin Waterfield states that Plato was not a nickname, but a perfectly normal name, and "the common practice of naming a son after his grandfather was reserved for the eldest son", not Plato. According to Debra Nails, Plato's grandfather was the Aristocles who was archon in 605/4.
Biography.
Plato was born in Athens or Aegina, between 428 and 423 BC. He was a member of an aristocratic and influential family. His father was Ariston, who may have been a descendant of two kings, Codrus and Melanthus. His mother was Perictione, descendant of Solon, a statesman credited with laying the foundations of Athenian democracy. Plato had two brothers, Glaucon and Adeimantus, a sister, Potone, and a half brother, Antiphon.
Plato may have travelled to Italy, Sicily, Egypt, and Cyrene. At 40, he founded a school of philosophy, the Academy. It was located in Athens, on a plot of land in the Grove of Hecademus or Academus, named after an Attic hero in Greek mythology. The Academy operated until it was destroyed by Sulla in 84 BC. Many philosophers studied at the Academy, the most prominent being Aristotle.
According to Diogenes Laërtius, throughout his later life, Plato became entangled with the politics of the city of Syracuse, where he attempted to replace the tyrant Dionysius, with Dionysius's brother-in-law, Dion of Syracuse, whom Plato had recruited as one of his followers, but the tyrant himself turned against Plato. Plato almost faced death, but was sold into slavery. Anniceris, a Cyrenaic philosopher, bought Plato's freedom for twenty minas, and sent him home. Philodemus however states that Plato was sold as a slave as early as in 404 BC, when the Spartans conquered Aegina, or, alternatively, in 399 BC, immediately after the death of Socrates. After Dionysius's death, according to Plato's "Seventh Letter", Dion requested Plato return to Syracuse to tutor Dionysius II, who seemed to accept Plato's teachings, but eventually became suspicious of their motives, expelling Dion and holding Plato against his will. Eventually Plato left Syracuse and Dion would return to overthrow Dionysius and rule Syracuse, before being usurped by Callippus, a fellow disciple of Plato.
A variety of sources have given accounts of Plato's death. One story, based on a mutilated manuscript, suggests Plato died in his bed, whilst a young Thracian girl played the flute to him. Another tradition suggests Plato died at a wedding feast. The account is based on Diogenes Laërtius's reference to an account by Hermippus, a third-century Alexandrian. According to Tertullian, Plato simply died in his sleep. According to Philodemus, Plato was buried in the garden of his academy in Athens, close to the sacred shrine of the Muses. In 2024, a scroll found at Herculaneum was deciphered, that supported some previous theories. The papyrus says that before death Plato "retained enough lucidity to critique the musician for her lack of rhythm", and that he was buried "in his designated garden in the Academy of Athens".
Influences.
Socrates.
Plato never speaks in his own voice in his dialogues; every dialogue except the "Laws" features Socrates, although many dialogues, including the "Timaeus" and "Statesman", feature him speaking only rarely. Leo Strauss notes that Socrates' reputation for irony casts doubt on whether Plato's Socrates is expressing sincere beliefs. Xenophon's "Memorabilia" and Aristophanes's "The Clouds" seem to present a somewhat different portrait of Socrates from the one Plato paints. Aristotle attributes a different doctrine with respect to Forms to Plato and Socrates. Aristotle suggests that Socrates' idea of forms can be discovered through investigation of the natural world, unlike Plato's Forms that exist beyond and outside the ordinary range of human understanding. The Socratic problem concerns how to reconcile these various accounts. The precise relationship between Plato and Socrates remains an area of contention among scholars.
Pythagoreanism.
Although Socrates influenced Plato directly, the influence of Pythagoras, or in a broader sense, the Pythagoreans, such as Archytas, also appears to have been significant. Aristotle and Cicero both claimed that the philosophy of Plato closely followed the teachings of the Pythagoreans. According to R. M. Hare, this influence consists of three points:
Pythagoras held that all things are number, and the cosmos comes from numerical principles. He introduced the concept of form as distinct from matter, and that the physical world is an imitation of an eternal mathematical world. These ideas were very influential on Heraclitus, Parmenides and Plato.
Heraclitus and Parmenides.
The two philosophers Heraclitus and Parmenides, influenced by earlier pre-Socratic Greek philosophers such as Pythagoras and Xenophanes, departed from mythological explanations for the universe and began the metaphysical tradition that strongly influenced Plato and continues today. Heraclitus viewed all things as continuously changing, that one cannot "step into the same river twice" due to the ever-changing waters flowing through it, and all things exist as a contraposition of opposites. According to Diogenes Laërtius, Plato received these ideas through Heraclitus' disciple Cratylus. Parmenides adopted an altogether contrary vision, arguing for the idea of a changeless, eternal universe and the view that change is an illusion. Plato's most self-critical dialogue is the "Parmenides", which features Parmenides and his student Zeno, which criticizes Plato's own metaphysical theories. Plato's "Sophist" dialogue includes an Eleatic stranger. These ideas about change and permanence, or becoming and Being, influenced Plato in formulating his theory of Forms.
Philosophy.
In Plato's dialogues, Socrates and his company of disputants had something to say on many subjects, including several aspects of metaphysics. These include religion and science, human nature, love, and sexuality. More than one dialogue contrasts perception and reality, nature and custom, and body and soul. Francis Cornford identified the "twin pillars of Platonism" as the theory of Forms, on the one hand, and, on the other hand, the doctrine of immortality of the soul.
The Forms.
In the dialogues Socrates regularly asks for the meaning of a general term (e. g. justice, truth, beauty), and criticizes those who instead give him particular examples, rather than the quality shared by all examples. "Platonism" and its theory of Forms (also known as 'theory of Ideas') denies the reality of the material world, considering it only an image or copy of the real world. According to this theory of Forms, there are these two kinds of things: the apparent world of material objects grasped by the senses, which constantly changes, and an unchanging and unseen world of Forms, grasped by reason (). Plato's Forms represent types of things, as well as properties, patterns, and relations, which are referred to as objects. Just as individual tables, chairs, and cars refer to objects in this world, 'tableness', 'chairness', and 'carness', as well as e.g. justice, truth, and beauty refer to objects in another world. One of Plato's most cited examples for the Forms were the truths of geometry, such as the Pythagorean theorem. The theory of Forms is first introduced in the "Phaedo" dialogue (also known as "On the Soul"), wherein Socrates disputes the pluralism of Anaxagoras, then the most popular response to Heraclitus and Parmenides.
The Soul.
For Plato, as was characteristic of ancient Greek philosophy, the soul was that which gave life. Plato advocates a belief in the immortality of the soul, and several dialogues end with long speeches imagining the afterlife. In the "Timaeus", Socrates locates the parts of the soul within the human body: Reason is located in the head, spirit in the top third of the torso, and the appetite in the middle third of the torso, down to the navel.
Furthermore, Plato evinces a belief in the theory of reincarnation in multiple dialogues (such as the "Phaedo" and "Timaeus"). Scholars debate whether he intends the theory to be literally true, however. He uses this idea of reincarnation to introduce the concept that knowledge is a matter of recollection of things acquainted with before one is born, and not of observation or study. Keeping with the theme of admitting his own ignorance, Socrates regularly complains of his forgetfulness. In the "Meno", Socrates uses a geometrical example to expound Plato's view that knowledge in this latter sense is acquired by recollection. Socrates elicits a fact concerning a geometrical construction from a slave boy, who could not have otherwise known the fact (due to the slave boy's lack of education). The knowledge must be of, Socrates concludes, an eternal, non-perceptible Form.
Epistemology.
Plato also discusses several aspects of epistemology. In several dialogues, Socrates inverts the common man's intuition about what is knowable and what is real. Reality is unavailable to those who use their senses. Socrates says that he who sees with his eyes is blind. While most people take the objects of their senses to be real if anything is, Socrates is contemptuous of people who think that something has to be graspable in the hands to be real. In the "Theaetetus", he says such people are "eu amousoi" (εὖ ἄμουσοι), an expression that means literally, "happily without the muses". In other words, such people are willingly ignorant, living without divine inspiration and access to higher insights about reality. Many have interpreted Plato as stating – even having been the first to write – that knowledge is justified true belief, an influential view that informed future developments in epistemology. Plato also identified problems with the "justified true belief" definition in the "Theaetetus", concluding that justification (or an "account") would require knowledge of "difference", meaning that the definition of knowledge is circular.
In the "Sophist", "Statesman", "Republic", "Timaeus", and the "Parmenides", Plato associates knowledge with the apprehension of unchanging Forms and their relationships to one another (which he calls "expertise" in dialectic), including through the processes of "collection" and "division". More explicitly, Plato himself argues in the "Timaeus" that knowledge is always proportionate to the realm from which it is gained. In other words, if one derives one's account of something experientially, because the world of sense is in flux, the views therein attained will be mere opinions. Meanwhile, opinions are characterized by a lack of necessity