First, God is not a thing, so let's rephrase that as God is logically and metaphysically necessary. Consider a person poking a stone around with a staff. The s

First, God is not a thing, so let's rephrase that as God is logically and metaphysically necessary. Consider a person poking a stone around with a staff. The stone moves only insofar as the staff moves it and the staff moves only insofar as the person moves the staff. Thus, the stone moves only insofar as the person moves it. Analogously, the existence of things, here and now and at any moment, must have a cause that is causing it to be here and now or at any moment. The cause of the existence of something here and now must be other than the thing itself because a thing cannot account for its own existence. If a thing could account for its own existence, then it would need to be identical with existence. But if a thing were identical with existence, then only it could exist and nothing but it. Furthermore, no change would be possible because if a thing is its own existence, then any change could only lead from existence to something that isn't existence, i.e., non-existence. So existence precedes things and things exist here and now because it is, like the person pushing the staff, causing them to be. We call this cause of existence God and if anything exists it necessary follows that there is a foundational cause and that is God.