The philosopher whose works include "The Republic" is Plato. In this foundational text, he explores the nature of justice, the ideal state, and the concept of the philosopher-king. Plato's allegory of the cave illustrates his views on knowledge and reality, emphasizing the importance of education in achieving a just society. His ideas on ethics, politics, and metaphysics have profoundly influenced Western thought and continue to be relevant in discussions about governance and morality.