The Ontological Argument is accredited to St. Anselm (1033-1109) and is formulated as such: God is “something than which none greater can be conceived;” or, God is the most perfect being that can be thought of. Anselm adds to this formulation a caveat—if God exists only in our minds, than a being greater than God can be thought of that exists in reality. For Anselm, to think of something being greater than God is impossible since, for Anselm, existence is a requirement for anything to be perfect. Thus, God must exist; “And certainly it exists so truly that it cannot be thought of as not existing.”
The greatest weakness of Anselm’s argument is that the word “perfect” is ambiguous, if not altogether vague. Epistemologically, we cannot verify that any concept that anyone has of perfection is indeed perfect. If we argue that human beings are inherently imperfect creatures (as the traditional Judeo-Christian interpretation of human beings maintains) it would seem to follow that they are incapable of thinking of anything as perfect. If we consider for a moment that each culture has relative standards of perfection (to say nothing of individuals), it seems that the Ontological Argument could just as well be a proof for polytheism, not just monotheism. That is, the Ontological Argument is not an argument for any particular god. Obviously, in considering his own culture as more perfect that any other, Anselm never considered this as a possibility.
It should also not go unnoticed how it seems Anselm arbitrarily requires existence for something’s perfection, meaning, we don’t know if he’s left out some additional requirement or if there is a requirement more important than existence that he’s neglected to mention or think of. We cannot be certain that perfection requires a thought-of object to actually exist, particularly when we have no experience with perfect things in our own experiences (low standard for perfection notwithstanding).
Our lack of experience with perfect things highlights a lesser observed problem with Anselm’s argument, namely that for something to exist is to place limitations upon the existent object. While the Abrahamic god is often given as a being “without limitation,” no one has definitively defined what “without limitations” actually means. In actuality, it doesn’t mean anything because we have no concept of things that do not have boundaries. To do so is an attempt to conceptualize nothingness, and we characterize nothingness as the space between objects and their inherent boundaries.
Fourth, as pointed out by the clever Austrian philosopher Douglas Gasking, an ontological argument can be used to show that God does not exist:
1. The creation of the world is the most marvelous achievement imaginable.
2. The merit of an achievement is the product of (a) its intrinsic quality, and (b) the ability of its creator.
3. The greater the disability (or handicap) of the creator, the more impressive the achievement.
4. The most formidable handicap for a creator would be non-existence.
5. Therefore if we suppose that the universe is the product of an existent creator we can conceive a greater being - namely, one who created everything while not existing.
6. An existing God therefore would not be a being greater than which a greater cannot be conceived because an even more formidable and incredible creator would be a God which did not exist.
7. God does not exist.
Lastly, we should consider our own existence and the existence of others for a moment. We exist yet we are not perfect. There is no reason to assume that any existent being who is more moral, more powerful, and/or more intelligent than us qualifies as perfect (even if they are closer to perfection as they exhibit these qualities). If perfection indeed requires existence and we know for certain that we exist, as opposed to a hypothetical god, it might be that we are more perfect than God by virtue of existence.