We explain who Plato was and what his most significant contributions were. In addition, we explore the stages of his thought and his relationship with Socrates.

Plato was disciple of Socrates and teacher of Aristotle.

Who was Plato?

Plato was an ancient Greek philosopher born in Athens, who lived between 427 and 347 BC. A disciple of Socrates and teacher of Aristotle, he is one of the most influential philosophers in the history of philosophy.

He is primarily known for having been the first philosopher to present his work in a rather systematic way. Among his most important ideas are: the theory of Forms (or theory of Ideas), the allegory of the cave and the famous Platonic dualism, which divides the world into a visible realm and an intelligible one.

In 387 BC he founded the Academy, a school of philosophy that lasted for 900 years and where mathematics, medicine, rhetoric and astronomy were taught, among other disciplines. Today the Academy is unanimously considered the first university in the Western world.

Plato's philosophy was compiled in various works, generally known as "Platonic dialogues" or “Plato’s dialogues” because of the way they are structured, which follows dialogue form. In them, Platonic concepts and ideas are presented through the different characters.

Traditionally divided according to the period in which they were written (youth, maturity and old age), most of the dialogues have Socrates as the main character. Only The Apology of Socrates, which presents his defense before the court that sentenced him to death, is not written in dialogue form.

Life of Plato

Plato was born in Athens around 428 BC and died in the same city in 348 BC, at the age of 80. Son of Ariston and Perictione, he grew up alongside his three siblings (Adeimantus, Glaucon and Potone) and a stepbrother, Antiphon, son of his mother and Pyrilampes, a former friend of Pericles. His family was wealthy and aristocratic, descendants of the ancient king Codrus on his mother's side, niece of Critias.

Plato’s actual name was Aristocles, but was given the nickname "Plato", a reference to his physical broadness. According to Diogenes Laërtius, the nickname was given to him by his wrestling coach and is translated as "he who has broad shoulders".

Initially trained in arts such as painting, poetry and drama, before meeting Socrates Plato frequented Cratylus, the philosopher who introduced him to the ideas of Heraclitean “becoming”. Aristotle maintains that the theory of Ideas stems from the intersection of the Heraclitean impossibility of knowledge and Socrates' pursuit of definitions.

At the age of twenty he met Socrates. From that moment and until the death of his teacher, he constantly frequented his circle, becoming his disciple and close friend. Most of Plato's works feature Socrates as the main interlocutor, in the role of teacher and guide of those with whom he converses, discusses and frequents. Although the degree of fidelity of the Platonic Socrates (i.e. the Socrates described by Plato) to the historical Socrates is debated, it is undeniable that Plato knew him deeply and was his most prominent disciple.

Socrates died in 399 BC. Plato was then 28 years old and after the death of his teacher, he traveled to Sicily and Italy, where he came into contact with the Eleatics and Pythagoreans, schools that would have influenced him greatly.

After his journey to Sicily, and after being sold into slavery by the tyrant Dionysius and ransomed by the Cyrenaic Anniceris, Plato returned to Athens and settled in the suburbs, where he bought a country estate and founded the Academy. It operated both as a school and a university until the Middle Ages, that is as a center of academic and religious activities, where the gods were worshiped and anyone seeking tutoring was instructed.

At the Academy and for twenty years, Plato was teacher of Aristotle, his most prominent and most disruptive pupil.

Plato died in 347 BC at the age of 80 in the city of Athens, after devoting the last years of his life to teaching and educating young thinkers, friends and politicians.

Plato's contributions

The theory of Ideas

The theory of Ideas or theory of Forms is one of Plato's most significant contributions to philosophy. Broadly speaking, it draws a clear distinction between what is perceived through the senses and what can be known through the intellect, which are ideas or the forms of things. The word "idea" comes from the Greek eidos (εἶδος) and can be translated as "form”, "aspect," "type," or "species," depending on the use.

The most comprehensive presentation of this theory is in Parmenides, one of Plato’s works allegedly from his late period. A more accessible explanation appears in the Republic, in the Allegory of the Cave. In both cases, the distinction is made between the visible world of the senses and the invisible or intelligible realm, where ideas dwell.

  • In the physical world are the things we know through the senses. These things are like images or traces of the forms or ideas in the intelligible world, which is inaccessible through the senses.
  • In the intelligible realm are the ideas of which sensible objects are imitations. Ideas are the object of study of dialectic as the supreme science, and sensible objects mirror them because, as Plato vaguely states, they "participate" in the ideas and resemble them in an imperfect, degraded form.

One of the major criticisms to the theory of Ideas was made by Aristotle himself, a disciple of Plato. Aristotle argued that, while it is true that the essence of things as well as their form is what defines them, form is not independent of things. For Aristotle, form is inseparably linked to matter, and together they compose substance.

The Allegory of the Cave

Mito de la caverna - Platón
The Myth of the cave exemplifies how the process of acquiring knowledge operates.

The Allegory of the Cave is an allegory, i.e. a symbolic literary representation whose aim is pedagogical-philosophical. Alongside the Chariot allegory, it is the most decisive allegory in the history of philosophy. It tells the story of a group of prisoners, born chained inside a cave where they could only see a back blank wall, upon which the shadows of the real world were projected.

Plato introduces the Allegory of the Cave at the beginning of Book VII of the Republic to explain the situation of humans in relation to knowledge. This text describes how both the physical world and the intelligible realm are perceived (the former through the senses and the latter through the soul, since like it in the intelligible world all things are eternal and immortal).

According to Plato, the prisoners who inhabit the cave, chained from birth, can only see the shadows that a fire hidden behind a wall reflects against the back of the cave. These shadows are produced by men walking along a corridor carrying different objects. The prisoners, unaware of where the shadows come from, believe they are the truth of things.

What the Allegory of the Cave holds is that if any of the prisoners were freed and turned their gaze towards the light of the fire, they would be confronted with a higher reality, which is the cause of the reality of the shadows. Eventually, the prisoner could escape to the outside of the cave where he would see a more perfect world, until forced to look directly at the sun. This would, however, blind him and if he wanted to return to the cave and free his companions, they would do nothing but mock him and, according to Plato, might even be capable of killing him (a clear reference to what happened to Socrates).

There are various interpretations of the allegory. Plato himself offers one towards the end of Book VI and in Book VII of the Republic. Possible explanations are epistemological (regarding knowledge), ontological (concerning being), educational, and even political. These interpretations remain an area of contention among scholars up to the present.

Platonic dualism

Platonic dualism is the conception of the body and soul as separate. In Plato, dualism spans to a division of the world into the perfect and the imperfect. If perfection is that which is immortal, everlasting, eternal, unchangeable and necessary, imperfection is that which is temporal, changeable and corruptible.

This results in the division between the physical world and the intelligible realm. The physical world is imperfect, formed by matter, to which the body is subject. All things that exist in the sensible world are made in the manner and likeness of the perfect, represented by forms in the intelligible realm. This is related to the soul, and is the place where things like it reside: like the soul, ideas are eternal, unchangeable and necessary.

From this separation arises the Platonic idea that the body is the prison of the soul and that with the end of the body, the soul is free and perfect once again until it reincarnates in a different body.

There are other possible interpretations or readings of dualism, such as its implications on knowledge: according to Platonic dualism, opinion (which is the form of sensible knowledge) is opposed to episteme (which is intelligible knowledge). This conception of knowledge is known as epistemological dualism.

Finally, it is possible to observe emerge even deeper traits of ontological dualism (the dualism which explains the separation of reality into two worlds), such as the problem of the interaction between both worlds, or the problem of anthropological dualism, for example, which sees the human being as a composite of body and soul and questions how this is possible.

The works of Plato

It is believed that Plato's entire body of work has survived intact to the present day. All of his works with the exception of the Apology of Socrates are written in dialogue form. Beyond the theme or question that concerns each one, most of the works present an explanation of the Socratic method, shown through the conversations between Socrates and the various interlocutors embodied in the people or famous thinkers of the time.

Although some are based on real facts, many of Plato’s dialogues are fictional scenarios created by Plato to provide the setting to postulate his various theses and fundamental ideas. Narrated in the form of myths or allegories, these ideas relate to the immortality of the soul (expounded in the Phaedrus), the myth of Eros (presented in the Symposium), and the example of the slave and reminiscence (which appears in Meno), among others.

While it is true that these works constitute the corpus of writings published during his lifetime, they should not be considered Plato's explicit teachings. The fact that they are narrated in dialogue form and through the use of myth and allegory indicates that, in any case, what is actually found there is material for interpretation. In addition to publishing his works, Plato taught orally at the Academy, and it is therefore believed that there is a written teaching, which is found in the dialogues, as well as an oral teaching, possibly dedicated to the exegesis (the philosophical interpretation of his ideas), reserved for his pupils.

Plato believed that the written language was only a copy of the spoken language, and the voice was the direct access to intelligence and knowledge accumulated in the soul, which was intelligible. This interpretative thesis is supported in Phaedrus, as well as in other works of Plato, such as the Seventh Letter, where he asserts that some things cannot be expressed in words. Nonetheless, the fact that Plato advocated oral teaching does not detract from the merit and philosophical prestige of his published works, a legacy that has survived to the present day.

Among Plato's most important works are:

  • The Apology of Socrates. It is the only Platonic text which is not written in dialogue form. It presents the trial and defense of Socrates before he is sentenced to drink the hemlock.
  • Gorgias. It is a dialogue that presents Platonic ideas regarding rhetoric, politics and justice.
  • Meno. It is the text in which the teaching of virtue and the idea of knowledge as reminiscence appear for the first time.
  • Phaedo. It is a text that deals with the immortality of the soul, a thesis defended by Socrates before his death, already in prison.
  • The Symposium. It is a text in which, during a banquet or dinner among friends, they discuss what is love is, its various myths and the erotic ascent proposed by Socrates to attain beauty.
  • The Republic. It consists of a reflection on the concept of justice and how it is expressed in the human being. It also includes the famous Allegory of the Cave, that of the sun, and other myths and metaphors.
  • Phaedrus. This dialogue focuses on the ideas of love, beauty and the destiny of the soul. It presents the Chariot allegory to explain the Platonic view of the soul.
  • The Timaeus. It is one of the last dialogues written by Plato, where he presents complex issues regarding cosmology and physics, such as the origin of the universe and of living beings.

Stages of Plato's thought according to his works

Plato's philosophical work, through his dialogues, is usually divided into four major periods:

  • Socratic period (393-389 B.C.). During this period Plato disseminated some of his theses based on the teachings of Socrates. In them he addresses concepts such as falsehood, piety and friendship. Some of his works published during this period were: Apology of Socrates, Crito, Ion or On Poetry, Lysis or On Friendship, Charmides and Protagoras.
  • Transition period (389-385 B.C.). During this period Plato founded the Academy, which proved key in deepening and developing sciences such as mathematics and astronomy. He postulated theories based on the teachings of Socrates and Pythagoras, and developed his own concepts about the immortality of the soul, virtue and language. Some of his works published during this period were: Hippias Major, Gorgias, Menexenus and Meno.
  • Maturity period (385-361 B.C.). In this period, which was the most outstanding, Plato developed his ideas on the immortality of the soul, the Theory of Reminiscence (which asserted the existence of certain innate knowledge in the human being), the Theory of Ascending Dialectics (which refined Socrates' maieutics and contemplated the cause-effect relationship of that which is observed), the concept of love (which opposed to "Platonic love") and his political philosophy. Some of his works published during this period are: The Republic, Phaedrus, Phaedo and The Symposium.
  • Late period (361-347 B.C.). During his old age, Plato made a thorough revision of the Theory of Ideas. This theory posits a duality of reality in the sensible world (what is perceived through the senses), and the intelligible realm (what can be known through the intellect). In addition, he explored concepts related to nature and medicine. Some of his works published during this period were: Parmenides, Theaetetus, Sophist and The Statesman.


  • Guthrie, W. (1988). Historia de la filosofía griega, vol. IV. Platón, el hombre y sus diálogos: primera época. Gredos.
  • Guthrie, W. (1988). Historia de la filosofía griega, vol. V. Platón, segunda época y la Academia. Gredos.
  • Guthrie, W. (1953). Los filósofos griegos. De Tales a Aristóteles. FCE.
  • Ross, W. D. (1993). Teoría de las Ideas de Platón. Cátedra.
  • Cordero, N. (2008). La invención de la filosofía. Una introducción a la filosofía antigua. Editorial Biblos.
  • “Plato” in Britannica.
  • “Una introducción a la Teoría de las ideas de Platón” in Universia.
  • “Platón” in Biblioteca Virtual Miguel de Cervantes.

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ESPÍNOLA, Juan Pablo Segundo. "Plato".
Encyclopedia of Humanities. 28 September, 2023,

About the author

Author: Juan Pablo Segundo Espínola

Bachelor of Arts in philosophy (University of Buenos Aires)

Translated by: Marilina Gary

Degree in English Language Teaching (Juan XXIII Institute of Higher Education, Bahía Blanca, Argentina).

Updated on: 28 September, 2023
Posted on: 28 September, 2023

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