I have previously written on the classical ontological argument on this blog, but this post I want to give a ontological argument that is a bit more contemporary and that I believe firmly to be valid and sound. Here it goes:
P1: I can think of the greatest possible being (G*)
P2: It is better to be necessary rather than not if one were G*
P3: G* entails that he will have every property that is better to have rather than not
P4: G* is necessary
C: G* exists and exists necessarily and we call this being God.
We know that P2 is true on the basis of intuition. We know a lot of things through intuition like mathematical, modal, and moral truths. But some intuitions we have to flush out and argue for. For me personally it is pretty obvious that it is better to be necessary rather than not, but for those of us that are not so convinced perhaps this argument might persuade you:
P5: It is better to be the precondition of moral facts rather than not
That is to say that morals exist because God exists. This would be through some sort of divine nature or divine command theory, whichever you think is more reasonable. Moral truths are necessary truths. It could never be okay for us to murder or rape. But in order for God to be the precondition of moral facts or truths God would have to be necessary. Necessity has to be true in order for P5 to be true then it seems that necessity is a precondition of P5. If something is great to have then it seems like all of the preconditions that make it to be are great to have. P5 is great to have and a precondition of it is Necessity therefore Necessity is great to have.
It seems then from this line of argumentation that it is more reasonable to believe in God rather than not. I will make further posts using this similar type of reasoning as to what this God is like in terms of features.