The Tripartite (JTB) Analysis of Knowledge

The idea that knowledge is something more than mere true opinion is already argued in Plato's Theaetetus (composed c. 369 BCE), where Socrates and Theaetetus jointly test, and ultimately fail to fully vindicate, the proposal that knowledge is "true belief with an account" (alethes doxa meta logou). Plato had earlier gestured at the same distinction in the Meno (97a-98a), using the image of Daedalus's statues, which were said to run away unless tethered down: true opinions, like those statues, are valuable but unstable until they are "tied down" by working out the reason why, an aitias logismos, at which point they become knowledge. Although the Theaetetus ends in aporia, without settling on a final definition, the dialogue fixed the basic shape of the problem for the entire subsequent tradition: knowledge requires truth, requires that the knower believe or assent to what is true, and requires some further ingredient, an account, reason, or warrant, that a merely true guess or lucky opinion lacks. This threefold shape is precisely what 20th-century epistemologists would later formalize as the tripartite, or JTB (justified-true-belief), analysis, treating Plato's logos as an early ancestor of the modern justification condition, even though Plato's own text considers and rejects several specific candidate senses of logos before leaving the question open.