How does justified true belief explain knowledge?

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Four colored straws in a glass of water appear bent at the water's surface, visually demonstrating the refraction of light. — Epistemology The refraction (bending) of light as it passes from air into water causes an optical illusion: straws in the glass of water appear broken or bent at the water's surface.

The traditional definition of knowledge as justified true belief originates from the work of Plato, particularly in his dialogue the Theaetetus.

Under this framework, knowledge requires three essential components:
* Truth: One cannot know what is false; therefore, a belief must be true to qualify as knowledge.
* Belief: One must hold the belief to be true.
* Justification: A true belief alone is insufficient for knowledge if it lacks a rational basis. For example, a lucky guess or a belief based on a dream that happens to come true lacks the necessary evidence or reasoning to be considered knowledge.

While this definition was widely accepted for centuries, it faced a significant challenge in the mid-20th century from the American philosopher Edmund L. Gettier. Gettier provided counterexamples demonstrating that a person can possess a belief that is both true and justified by evidence, yet still fail to have knowledge because the belief is not properly or causally connected to the truth of the matter.1