There must have been a first cause, which caused something else, which caused something else, and so on. However, the very first cause had to have been uncaused. Only a supreme being can be uncaused, as nothing finite can cause itself. Therefore, the first cause was God. Again, everything that exists was caused by something else. The universe exists, so the universe has a cause of existence. The cause of its existence is God, so God exists. This is the cosmological argument as believed by Plato and Aristotle. Aquinas called this idea The Argument from Causality, as the universe follows a “cause and effect” pattern. All effects are caused by an event, which will turn out to be the effect of another cause.