Plato is perhaps the most significant philosopher who ever lived and The Republic, composed in Athens in about 375 BC, is widely regarded as his most famous dialogue. Its discussion of the perfect city--and the perfect mind--laid the foundations for Western culture and has been the cornerstone of Western philosophy. As the distinguished Cambridge professor Simon Blackburn points out, it has probably sustained more commentary, and been subject to more radical and impassioned disagreement, than almost any other text in the modern world.