As a firm believer in the Christian God, and one who finds the other popular theistic arguments to be solid, I believe our case is much stronger without the Ontological Argument. If its logic isn't sound, and the sneaking suspicion that there is something not quite right is justified, it can weaken our credibility in defending those arguments and evidences we present that are valid. As we point skeptics to the truth, we need to shed everything that is false, including those parts of our case that may lend support to it, if only they were true. So while I may be attacking a part of our cumulative case, I believe the whole would be much stronger without it.
So for those unfamiliar with the Ontological Argument, what is it? The word "ontology" is briefly defined as "the study of being." So when we speak of ontology in relation to God, it refers to what it means to be God; the qualities God possesses that makes Him God. The OA attempts to show that by God's very nature, He necessarily exists. In short, the argument states that if it is POSSIBLE that God exists, then He MUST exist. Originally developed and popularized by the 11th century theologian, Anselm of Canterbury, the argument has been controversial among both skeptics and believers throughout the centuries. Anselm's version is framed around the concept of the "greatest conceivable thing." If that thing is able to be conceived in the mind of an individual, then its greatness must be actual, because something that exists in the mind alone is not as great as something that also exists in reality. His original argument has been revised and improved for clarity throughout the centuries, most recently taking the form constructed by Christian philosopher Alvin Plantinga, and reworded by William Lane Craig. This "modal" version defines God as a "maximally great being." Since this is the version most commonly used in contemporary apologetics, I will present it below and point out where I find it to be flawed.
The Modal Ontological Argument
Premise 1: It is possible that a maximally great being exists.
Premise 2: If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.
Premise 3: If a maximally great being exists in some possible world, then it exists in every possible world.
Premise 4: If a maximally great being exists in every possible world, then it exists in the actual world.
Premise 5: If a maximally great being exists in the actual world, then a maximally great being exists.
Conclusion: Therefore, a maximally great being exists.
(Here's a great animation video to further explain it.)
Most skeptics attack premise 1, comparing the idea of a maximally great being to such things as a maximally great pizza. How would you define such a thing? Isn't maximal greatness a matter of personal opinion, just like what would be the perfect pizza? How many slices of pepperoni? Would you add pineapple? As someone who affirms the Christian understanding of God's maximally great qualities (omnipotence, omniscience, omnipresence, and omnibenevolence), I will defend the idea of a maximally great being (MGB), and why it is different than the pizza.
The skeptic relies on subjectivity (personal viewpoint) in determining what God is, yet it is their own subjectiveness that rules out the possibility of God's existence. By saying that the MGB is impossible, they carry the burden of proof in showing that such a concept is impossible. However, maximal greatness is not in itself a matter of OUR determination. Sure, we may all define it differently, but that doesn't mean there isn't an objective standard of greatness that exists. We are in no position to conclude that our own disagreements about what it means to be maximally great rules out the possibility of maximal greatness. Add to this the fact that many fellow human beings think it IS possible for God to be maximally great. So the skeptic who says it ISN'T possible must be absolutely certain that his own conclusion is correct, and those who disagree are wrong. The burden of proof lies with the skeptic to show that he is an infallible determiner of what is true. If he is wrong about anything, then that means that he can be wrong about his conclusion that maximal greatness is impossible. Therefore if it is possible that he is wrong, it remains possible that a maximally great being exists, and the skeptical objection to premise 1 fails.
Premise 2 simply states that if God might exist, then there is a "possible world" where He will exist. This is the obvious conclusion of premise 1. If He exists, then there exists a world He exists in. Likewise, if He doesn't exist, there exists a world where He is absent. So far so good.
This leads us to premise 3, and this is where things get really interesting. The premises that follow are obvious, as well as the conclusion. It all hangs on this. "If a maximally great being exists in some possible world, then it exists in every possible world." The underlying assumption here is that maximal greatness implies the necessity of existence. If God is maximally great, He MUST exist in every possible world. But is this really true? I don't think so, and this is why I believe the Ontological Argument fails.
To understand why, let's go back to premise 1. "It is possible that a maximally great being exists." Yes, we decided that it is possible. However, when considering the possibility, we are also considering alternate possibilities. As Christians, we must also consider the possibility that the God of Islam exists, or the pantheistic God of Hinduism exists, or the created God of Mormonism exists, and so on and so on. We must also consider the possibility that no God exists, or that there is a "world" of complete nonexistence. These all exist in the realm of "possible worlds." Unless these ideas are shown to be logically impossible, they must be admitted into the potentially infinite set of possible worlds that might exist.
So when we jump from the MGB existing in one possible world to Him necessarily existing in every possible world, we end up with some absurd situations. For example, we end up with the MGB existing in a world where Allah also exists. If Allah exists as well as the Christian God, doesn't that compromise what it means for God to be God? Doesn't maximal greatness entail the fact that God is God over all things, and there is no other? Yet Allah is also understood to be the one and only God over all things. So we have a contradiction. This becomes even more apparent when we consider the possible world where no God exists. Must the Christian God exist in an atheistic world? This is absurdity! So when the third premise is applied to the original set of possible worlds implied in premise one, we can see that there must be something off here. Just how do we put our finger on it?
I would suggest that the key error is the underlying assumption that if God's existence is necessary in this world (and I believe this to be the case), then His existence is necessary in all those possible worlds we can imagine in our minds. Those imaginary worlds may not really be "possible," but we cannot show them to be logically incoherent and therefore impossible without begging the question in claiming that the MGB is necessary for any world to exist.
So what do we mean when we say that God's existence is necessary? I don't see how we can understand what is necessary without appealing to what is contingent. We say there must be a cause when we see an effect. Without the effect, we cannot infer the cause. When we look at this world we live in, we see evidence that points us back to a cause. We use the Kalam Cosmological Argument to understand that this cause is spaceless, timeless, and immaterial. We use the Teleological (Fine-tuning) Argument to understand that this cause is a mind. We use the Moral Argument to conclude that this cause is personal and is morally good. These arguments point to the Christian God's necessity in the world we live in, for it cannot account for the qualities it possesses on its own. But what if the world didn't possess these qualities? What if, for example, the world was morally neutral, and we didn't have a concept of right and wrong? Could we conclude that there was an omnibenevolent God? What if the world was uninhabitable and chaotic? Could we conclude that He is a mind, and therefore omniscient? We could then have a god who is omnipotent, but not omniscient or personal. This is not the MGB. So it seems that we understand the necessity of the MGB's existence by the world we live in, and cannot make a rational case for Him apart from it.
Where the Ontological Argument ultimately fails is in assuming that God must necessarily exist in worlds that don't. There is no reason to assume this, other than a faulty understanding of necessary existence. This still leaves us with a potentially infinite number of worlds in which the Christian God could exist, but all of these are a subset of worlds taken from the greater ensemble of worlds that don't exist, but are logically possible. These are the possible worlds which the MGB could have created, had He so desired. As someone who affirms that God knows everything, including all possible worlds He could have made, I don't believe that this actual world must be as it is, but exists as it is because God decided to create it this way. However, whatever world He could have created would have also been consistent in reflecting who He is. Just as a story is reflective of its author, so too our world is a reflection of its Creator.
We can conclude that the Christian God is that Creator, but I don't believe we can do so through the Ontological Argument. It is a thoroughly fascinating idea, but I'm afraid it doesn't succeed in its objective. I'm open to being wrong about this, but I'd ask that the Christian apologist also be open to the possibility that this just doesn't work. We have plenty of good material to make our case. We don't need the Ontological Argument, and we will be more effective without it.
