In this blog, I would like to introduce the cosmology of the ancient Athenian philosopher Plato. His cosmology was the first systemic and complete cosmology in the history. He and his most famous student Aristotle both hold the geocentric view of the universe, and their perspectives of the universe were influential in the following thousands of years, although many disagreements exist between their theories.
In Plato’s philosophy, the perfect things only exist in the ideal realm, but not in the reality. The material world is only a defective copy of the ideal world. This concept also applies to his view of our universe. He believes that the universe we live in was created by an artificer named Demiurge, a god who is completely “good” and “fair.” He created the world based on his knowledge about the ideal form of the universe. Unlike our modern understanding of atoms, Plato states that the universe is made up of only four pre-existing basic elements: fire, earth, water, and air. He denies the possibility of multiverse, because he considers the god demiurge used up all the basic elements to create the world, so nothing was available out there for another universe.
In Plato’s model of our solar system, Earth is located at the center. The Sun and all other planets orbit Earth in the complete circular motion. In fact, many ancient philosophers, including Plato and Aristotle, worship circle. They regard it as a representation of perfectness. However, an important part in Plato’s cosmology is similar to our modern understanding of the universe: humans are not central. Plato thinks that all the celestial bodies created by demiurge are also eternal gods. Human beings were not created by demiurge directly, but by these celestial bodies in the heaven. The soul of humans was diluted in the creation process. As a result, we are not immortal in the beginning. Nevertheless, Plato still believes that humans are connected to divinity. He says that if humans live proper life to conquer their passions and physical pleasures, they are said to be successfully implementing rational thoughts. As a reward, they will ascend to heaven after they die, and their soul will become eternal just as stars and planets in the universe.