Theaetetus

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Theaetetus

work by Plato

Also known as: “Theaetetōs”

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June 11, 2026

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The Theaetetus is a dialogue by Plato that primarily features the Athenian mathematician Theaetetus as its main character. The dialogue explores the nature of knowledge, with Plato critiquing an empiricist theory of knowledge and anticipating later philosophical ideas.123

Theaetetus himself was a significant figure in Greek geometry, known for his work on incommensurables and the classification of Platonic solids. Plato's dialogue uses Theaetetus's contributions as a backdrop to delve into deeper philosophical questions about how we acquire knowledge and the distinction between the changing world of senses and the unchanging world of Forms.1234

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Plato
Late dialogues of Plato
The Theaetetus considers the question “What is knowledge?” Is it perception, true belief, or true belief with an “account”? The dialogue contains a famous “digression” on the difference between the philosophical and worldly mentalities. The work ends inconclusively and may indeed be intended to show the…
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The Theaetetus considers the question “What is knowledge?” Is it perception, true belief, or true belief with an “account”? The dialogue contains a famous “digression” on the difference between the philosophical and worldly mentalities. The work ends inconclusively and may indeed be intended to show the…
Read More

Western philosophy
Philosophy
…his later dialogues, especially the Theaetetus, Plato criticized an empiricist theory of knowledge, anticipating the views of 17th-century English philosophers such as Thomas Hobbes (1588–1679). In the Timaeus, Plato tried to construct a complete system of physics, partly employing Pythagorean ideas.
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…his later dialogues, especially the Theaetetus, Plato criticized an empiricist theory of knowledge, anticipating the views of 17th-century English philosophers such as Thomas Hobbes (1588–1679). In the Timaeus, Plato tried to construct a complete system of physics, partly employing Pythagorean ideas.
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Theaetetus
…subject of two dialogues—Theaetetōs (Theaetetus) and Sophistēs (Sophist)—the former being the major source of information about Theaetetus’s life, including his death in a battle between Athens and Corinth in 369 bc.
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…subject of two dialogues—Theaetetōs (Theaetetus) and Sophistēs (Sophist)—the former being the major source of information about Theaetetus’s life, including his death in a battle between Athens and Corinth in 369 bc.
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$optical illusion: refraction of light$
epistemology
Plato
…general be defined? In the Theaetetus Plato argues that, at a minimum, knowledge involves true belief. No one can know what is false. People may believe that they know something that is in fact false. But in that case they do not really know; they only think they know. Knowledge…
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…general be defined? In the Theaetetus Plato argues that, at a minimum, knowledge involves true belief. No one can know what is false. People may believe that they know something that is in fact false. But in that case they do not really know; they only think they know. Knowledge…
Read More