Knowledge is true opinion.

The quote, “Knowledge is true opinion,” is attributed to Plato, the ancient Greek philosopher and student of Socrates. It reflects one of the central themes in Plato’s dialogues: the nature and definition of knowledge. In works such as Theaetetus and Meno, Plato explores whether knowledge can be equated with true opinion or whether something more is required for an opinion to rise to the level of knowledge. This discussion laid the foundation for centuries of philosophical inquiry into epistemology, the study of knowledge.

The phrase “true opinion” suggests that when a person holds a belief that aligns with reality, it can be considered a form of knowledge. However, Plato complicates this idea by asking whether true opinion alone is sufficient. For example, someone might have a correct belief about how to reach a destination without understanding why the route works. In this sense, true opinion may guide action effectively, but Plato questions whether it qualifies as genuine knowledge without justification.

In the Meno, Plato distinguishes between true opinion and knowledge by arguing that knowledge is “tied down” with reasoning or explanation, making it stable and reliable. Without this grounding, true opinions may be correct but are unstable—they can shift or be forgotten. This distinction became the basis for the classical definition of knowledge as “justified true belief,” a concept that has shaped Western philosophy for centuries.

Ultimately, the quote underscores Plato’s view that while true opinion is valuable, especially in guiding decisions, it is not the same as knowledge. For Plato, real knowledge requires both truth and understanding, supported by reasoning that connects belief to reality in a lasting way. This exploration continues to influence modern debates on what it means to truly “know” something.