"Timaeus" and "Critias" are two dialogues written by Plato in the 4th century BC. They are part of his tetralogy of works on the nature of reality, which also includes the "Republic" and the "Sophist." In "Timaeus," Socrates and his friends discuss the nature of the universe and the role of the gods in its creation. The dialogue centers around the speech of Timaeus, a Pythagorean philosopher, who presents a cosmology based on mathematical principles. According to Timaeus, the universe is a living organism created by a divine craftsman, who used the five basic elements of earth, water, air, fire, and a fifth element called "aether" to form the cosmos. The gods, including the Demiurge, are responsible for maintaining the order of the universe and the harmony of the cosmos. In "Critias," Socrates and his friends discuss the ancient civilization of Atlantis, which is said to have existed over 9,000 years ago. The dialogue centers around the speech of Critias, a relative of Plato, who describes the history and culture of Atlantis as recounted to him by his grandfather. According to Critias, Atlantis was a powerful and advanced civilization that eventually became corrupt and was destroyed by the gods in a catastrophic event. The dialogues raise important philosophical questions about the nature of reality, the role of the gods in the cosmos, and the possibility of an ideal society. They have had a lasting impact on Western philosophy and literature and have inspired numerous works of art, literature, and film.