7.2.1 Plato and the Traditional Account of Knowledge

Plato, one of the most important of the Greek philosophers, hypothesized that knowledge is justified true belief. Plato’s analysis is known as the traditional account of knowledge. Plato’s definition is that a person S knows proposition P if and only if

1. P is true,
2. S believes P, and
3. S is justified in believing P (Plato 1997b).

Plato’s hypothesis on knowledge, often referred to as the JTB account (because it is “justified true belief”), is highly intuitive. To say “John knows P, but he does not believe P” sounds wrong. In order to know something, a subject must first believe it. And one also cannot say “Ali knows P, but P is false.” A person simply cannot have knowledge of false things. Knowledge requires truth. Last, someone should not claim to know P if they have no reason to believe P (a reason to believe being justification for P).