The Five Ways of St. Thomas Aquinas, Part III: The Third Way
The Third Way – The Argument from Necessity
Building upon the Argument from Efficient Cause, the Third Way demonstrates that there are things that are non-necessary, (meaning that it’s possible for them “not to be,”) and which are caused by a necessary thing that “has to be.”
This argument says that whatever has been brought into existence has not always existed, and will not always exist. Thus, the existence of everything is contingent upon something outside of itself, a necessary thing, to bring it into, and keep it in existence. These things are possible, but not necessary.
Therefore, if everything is possible