Thomas Aquinas famously formulated his version of the cosmological or "first cause" argument. According to this argument, the things which we see around us now are the products of a series of previous causes. But that series cannot go back in time forever. Thus there must be some first cause which was not itself caused by anything else. And that first uncaused cause is God.
A lot of the argument is based on Aristotelian views, of that there is a greater being that started the infinite regression of the earth, an ‘unmoved mover’.
Aquinas wrote about the ‘5 ways’ or Quinque Viae to help establish his argument based on observation and evidence that there is proof of a ‘summum bonum’. The first three ways are concerning the cosmological argument. The first way concludes that there must be an unmoved mover, infinite regression of the universe must been started by something and Aquinas believes that this unchanged changer is God. There must be a prime mover to change things between potentiality to actuality. Aquinas himself quotes that “The chain of movers cannot go on to infinity because then there would be no first mover and consequently no other mover”.
The second way explains that there must be an uncaused causer as nothing can cause itself to exist if it does not already, something must have caused the chain of infinite regression. The third way concludes that everything in the universe is contingent on something for existence, for example, babies are contingent on their parents, and without them they would die. If everything is contingent, there must be a necessary being that created the universe into existence. The prime mover, God, is an exception as he is not contingent on anything; God exists outside time and space.
However, although Thomas Aquinas felt that he had good evidence to prove his theory about God existing, many people critisised the Quinque Viae. David Hume, a famous