Aquinas' Argument for the Existence of God From Contingent Being

Aquinas thinks it's philosophically unprovable whether the world began to exist or an not. He distinguishes between causes of being and causes of becoming. If we think of a chandelier hanging in a particular place, you say, why is it here? Not how did it come to be but just simply to be. We can still give an argument for the existence of God without referring to a beginning of the world.