Their dialogue covers many questions, such as: is knowledge purely subjective, composed of the ever-changing flow of impressions we receive from the outside world? Is it better thought of as true belief'? With skill and eloquence, Socrates guides the debate, drawing out the implications of these theories and subjecting them to merciless and mesmerising criticism. One of the founding works of epistemology, this profound discussion of the problem of knowledge continues to intrigue and inspire.

The Theaetetus is one of Plato's dialogues concerning the nature of knowledge, written circa 369 BC. In this dialogue, Socrates and Theaetetus discuss three definitions of knowledge: knowledge as nothing but perception, knowledge as true judgement, and, finally, knowledge as a true judgement with an account. Each of these definitions is shown to be unsatisfactory.

Plato (428/427 or 424/423 – 348/347 BCE) was a philosopher, as well as mathematician, in Classical Greece. He is considered an essential figure in the development of philosophy, especially the Western tradition, and he founded the Academy in Athens, the first institution of higher learning in the Western world. Along with his teacher Socrates and his most famous student, Aristotle, Plato laid the foundations of Western philosophy and science.