I have a love hate relationship with this argument. As it is most commonly quoted, it appears like something Lewis Carroll would write, some meaningless, circular nonsense straight from fairy land: God is the best; a quality of being best is existence; so, God exists. Starting with the premise that God exists and moving to the conclusion that God exists doesn’t seem to get us very far. But, I think, this is a misunderstanding of the argument.
I have used this argument once with a friend questioning God’s existence, but I was not so clever that I tried to do it verbally. I wrote it out, making sure to be very precise and delicate in what I said. To sum up, I argued that we had a dilemma in life: Does life have purpose or not (teleological). Giving reasons for why I believed there to be an ultimate meaning to life, I posited that whatever this ultimate good was, it fit the definition of God.
To the point of the Ontological argument: I found, when just talking with my friend, that he didn’t have a good definition of God that he could either accept or reject. His was a muddied accumulation of ideas about God which possessed no fundamental aspect. When appealing to the Ontological and Teleological arguments together, I was arguing that my friend already believed in an ultimate good (he had accented to moral reality) and that whatever he was positing as that ultimate good (in other words, he believed this ideal existed in some way) fit the definition of God. So, standing on its own, the Ontological argument didn’t prove God existed directly, but helped to prove that something which did exist, the ultimate good based off of the teleological argument, was God.
Or maybe I don’t understand the Ontological argument at all.
This argument always seems so powerful to me that I do not understand the dismissal of it. However, people disagree with me on this. I think it is reasonable to discount infinite regresses as obviously impossible. A circular causation I’d be more willing to accept, but even then, appreciating nature, the self-contained cycles we do perceive do not account for their own existence, only their own continuance. The wheels of nature turn, yes, but the energy turning those wheels pass away and eventually expire. A turning wheel still needs a source, a first cause.
I remember bringing this argument up once, only to be interrupted and told, “Aliens might arrive at any moment and contradict me.” (True story. She was arguing, basically, for the impossibility of ultimate knowledge of anything, at least as regarded anything I said. It was another matter when she made claims to truth). The conversation did not get very far. Similarly, I have not found anyone quite as moved by this reasoning as I am. I think, due to its philosophical nature, it is not very useful in changing modern minds which on the whole seem to be mostly sophistic and are more concerned with arriving at a desired conclusion than letting reason lead where it leads. I am not herein dismissing honest objections to the cosmological argument, only stating that I have not experienced in person someone who rationally argues against it. I have not found it very useful in my day and age, and I think this is because it is, metaphorically, too dry of an argument—it is too dispassionate to be the main course, but it may make a good side dish.
I also find the teleological argument powerful, but not on the whole a slam dunk. It points towards God, but it does not necessitate Him. Speaking of my own life, almost every teacher who wasn’t a Christian, no matter the subject, in all my early schooling and later in high school, seemed intent upon assaulting the Teleological argument. Whether their arguments were good or bad, at this point I’m not concerned: The problem is that most of my generation takes it for granted that the Teleological argument is wrong, and as such, though I think it is a good argument, it is not wise to use. It is expected, and ears are already plugged against it. As such, the Ontological argument, being hard and confusing at times, lends itself to a certain quality of freshness. Many have never heard it, and hearing it, may be hearing it for the first time apart from any prejudices.