Plato's Theaetetus: What Is Knowledge? › The Second Definition: Knowledge Is True Belief

Having abandoned perception, Theaetetus offers a second definition: knowledge is true belief (*alēthēs doxa*). This seems more promising. Knowledge is not mere perception but a judgment that gets things right. When I believe that Athens is in Greece and Athens actually is in Greece, I know it. This definition captures something important. Knowledge does seem to require getting things right. A false belief is not knowledge, no matter how confident we feel. But Socrates raises a telling objection through what has become known as the "jury argument." Consider a jury in a law court. A skilled orator persuades them that the defendant committed a crime. Suppose the defendant actually did commit the crime. The jury now has a true belief about the defendant's guilt. But do they have knowledge? Socrates argues they do not. The jury was not present at the crime. They did not see what happened. They have been persuaded by rhetoric, not by direct acquaintance with the facts. Even though their belief happens to be true, it seems wrong to say they *know* the defendant is guilty. They have been convinced, not informed. This argument introduces a distinction that would later become central to epistemology: the difference between merely true belief and justified true belief. The jury's belief is true but not justified in the right way. They arrived at it through persuasion rather than through evidence or reasoning that connects them to the facts. ::: {.callout-note title="The Gettier Problem Anticipated"} Plato's jury argument anticipates by over two millennia the famous "Gettier cases" that shook twentieth-century epistemology. Edmund Gettier showed that one can have justified true belief without having knowledge, when the justification and the truth are connected only by luck. Plato saw the basic problem: truth and belief are not enough. ::: The failure of the second definition points toward what seems missing: some account of how the belief is formed, some connection between the believer and the truth that makes the belief more than accidentally correct.