The ancient philosopher known for his work on the nature of knowledge is Plato. A student of Socrates, Plato explored epistemology and metaphysics extensively. His dialogues often address forms of knowledge, belief, and the distinction between the perceived reality and the true forms, particularly in "The Republic." In this work, he examined how knowledge can be attained and the role of philosophers as the ideal rulers. His allegory of the cave illustrates the journey from ignorance to enlightenment, emphasizing the importance of education and the pursuit of truth to achieve genuine understanding.