The term "cosmological" derives from the word "cosmos", meaning "the universe". It is an inductive argument which starts from experience, from specific matter to a general conclusion. The argument works on the basis of observation, meaning that the latest observation may well show that all previous observations have led us to the wrong conclusion. The cosmological argument is a posteriori argument (truth of a proposition may only be known to be true after empirical evidence has been used to prove the proposition true or false), that starts from the existence of the universe (something we experience) and tries to prove from this that God exists. Although the steps in the Cosmological argument may be challenged but its start (from an invulnerable first premise which we all accept, - the existence of the universe) is undoubted. .
Natural theology tries to demonstrate that "God exists" is true by showing that word "God" successfully refers to that which exists independent of the created universe and on which this universe depends for its existence. Aquinas a Catholic theologian argues for the existence of God, his most important argument is probably the "Third Way" - the argument from contingency and necessity. The argument seeks to establish dependence, the dependence of the universe and the world on God. Aquinas's argument is that in nature things can either exist or not exist. If this is so, given infinite time, at some time everything must not be. If there was once nothing, nothing can come from it and therefore something must necessarily exist. Everything necessary r4. Everything necessary must be caused or uncaused. The series of necessary things cannot go on to infinity, as there would then be no explanation for the series. Therefore there must be some Being "having of itself its own necessity", which everyone calls God. .
Aquinas" argument arrives at this Being "having of itself its own necessity" explains the origin of the Universe i.