Timaeus and Critias includes two of Plato's dialogues which were designed to be part of a trilogy. Unfortunately the philosopher did not complete the work. Timaeus and Critias utilize select men to theorize on the natural world and to tell a story of the lost city of Atlantis. Timaeus speculates on the nature of the physical world, the purpose of the universe, properties of the universe, the creation of the world soul, the elements, and the golden ratio. It is followed by the dialogue Critias, which tells the tale of the powerful island kingdom of Atlantis. It is interesting that the only existing written records referring to Atlantis are in these dialogues. Critias and Timaeus entertain Socrates with a story that is "not a fiction, but true."