Plato was an ancient Greek philosopher, mathematician, and writer known for his Socratic dialogues. He believed that the material world is not the real world, but rather an image or copy of the real world of ideal forms. Plato also asserted that societies have a tripartite class structure corresponding to the appetite, spirit, and reason parts of the individual soul. This includes productive workers, protective warriors, and a small governing class of philosopher kings who rule using reason.