The philosopher known for his work "The Republic" is Plato, an ancient Greek thinker who lived from approximately 427 to 347 BCE. In this seminal text, Plato explores the nature of justice, the ideal state, and the philosophy of governance through dialogue, primarily featuring his teacher Socrates. "The Republic" introduces the concept of philosopher-kings who possess the wisdom to rule justly, advocating for a society governed by reason rather than by mere popular opinion. It is foundational in Western philosophy, influencing various fields including political theory, ethics, and education across centuries.