Probably around 369 BCE

Plato — A dialogue that leaves the definition open

If knowledge is perception, true judgment, or true judgment with an account, why does the dialogue stop without settling on one?

Evidence-backed account

The Theaetetus successively tests candidates that identify knowledge with perception, true judgment, and true judgment with an account.

Open evidence

This is an evidence-linked editorial paraphrase, not a direct quotation.

Theaetetus
Plato · Perseus Digital Library text with Stephanus pagination
Locator: Stephanus 151d–187a, 187b–201c, 201d–210a
Open source
Plato on Knowledge in the Theaetetus
Stanford Encyclopedia of Philosophy
Locator: Sections 6–8
Open source

The dialogue ends in aporia without endorsing any of the three candidates as its final definition of knowledge.

Open evidence

This is an evidence-linked editorial paraphrase, not a direct quotation.

Theaetetus
Plato · Perseus Digital Library text with Stephanus pagination
Locator: Stephanus 210a–b
Open source
Plato on Knowledge in the Theaetetus
Stanford Encyclopedia of Philosophy
Locator: Introduction and section 9
Open source

The dialogue is commonly dated to around 369 BCE; no exact place of composition is asserted.

Open evidence

This is an evidence-linked editorial paraphrase, not a direct quotation.

Plato on Knowledge in the Theaetetus
Stanford Encyclopedia of Philosophy
Locator: Introduction, date and dramatic frame
Open source