Medieval Arguments for the Existence of God Part 2: Ontological Arguments

This is part 2 of a four-part series on the medieval arguments for the existence of God. Part 1 covered the four categories of arguments for God’s existence, the philosophical problems of faith, and key terminology relevant to the debate. This post will cover the ontological argument exclusively, while parts 3 and 4 will cover the cosmological and teleological arguments, respectively. 


The ontological argument, originally developed by St. Anselm of Canterbury (1033/4–1109) in the Proslogium, purports to demonstrate the existence of God using logic alone. Just as a square circle cannot exist based on how we define a circle, the assertion that God does not exist likewise contradicts our very definition of God. The basic argument is that we conceive of God as a being than which none greater can be conceived, and since a being that exists is greater than a being that does not exist, God must necessarily exist. 

The weakness in this line of reasoning was recognized immediately, as when Gaunilo of Marmoutier, a contemporary of Anselm, demonstrated the absurdity of defining things into reality (he used the example of the “perfect island” that must exist). Centuries later, Immanuel Kant would show that existence does not function as a predicate, and that the instantiation of predicates (omniscience, omnipotence, omnibenevolence) in a subject (God) simply assumes that the subject first exists. Existence isn’t a property; it’s a metaphysically necessary condition for the instantiation of any properties. 

And so it makes little sense to say that a being that exists is “greater” than a being that does not exist, as if existence were a property, like height, that you could add to, measure, or increase. Perhaps it is the case that it is not possible to conceive of God as being nonexistent, but conception alone does not necessitate existence. 

Additionally, as philosopher Norman Malcolm pointed out, this kind of talk is very bizarre. I might say, for example, that my son will be a better or “greater” man if he is honest or courageous or kind. But what could it mean to say that my son would be a greater man if he exists?

While these objections demonstrate the problems associated with conceiving things into reality, a different line of reasoning uses the logic of the ontological argument to reach the opposite conclusion—that God cannot exist, and that the ontological argument is self-contradictory.

The Devil Paradox

First, here’s a summary of the ontological argument, taken from the Internet Encyclopedia of Philosophy:

  1. It is a conceptual truth (or, so to speak, true by definition) that God is a being than which none greater can be imagined (that is, the greatest possible being that can be imagined).
  2. God exists as an idea in the mind.
  3. A being that exists as an idea in the mind and in reality is, other things being equal, greater than a being that exists only as an idea in the mind.
  4. Thus, if God exists only as an idea in the mind, then we can imagine something that is greater than God (that is, a greatest possible being that does exist).
  5. But we cannot imagine something that is greater than God (for it is a contradiction to suppose that we can imagine a being greater than the greatest possible being that can be imagined.)
  6. Therefore, God exists.

Now, consider this version regarding the existence of the Devil.

  1. It is a conceptual truth (or, so to speak, true by definition) that the Devil is a being than which none more evil can be imagined (that is, the most evil possible being that can be imagined).
  2. The Devil exists as an idea in the mind.
  3. A being that exists as an idea in the mind and in reality is, other things being equal, more evil than a being that exists only as an idea in the mind.
  4. Thus, if the Devil exists only as an idea in the mind, then we can imagine something that is more evil than the Devil (that is, a more evil possible being that does exist).
  5. But we cannot imagine something that is more evil than the Devil (for it is a contradiction to suppose that we can imagine a being more evil than the most evil possible being that can be imagined.)
  6. Therefore, the Devil exists.

The ontological argument demonstrates, therefore, that the greatest possible being (God) and the most evil possible being (the Devil) must both exist, and must both be all-powerful and all-knowing (the devil must be all-powerful, otherwise a more evil being could be conceived). But two all-powerful beings coexisting in the same universe is a logical contradiction (if one being is more powerful than the other, the other cannot be all-powerful); therefore, the ontological argument refutes itself by its own logic, showing that both God and the Devil do not and cannot co-exist. 

Additional logical problems

It has also been pointed out that the idea of a perfect being (who is all-powerful, all-knowing, and all-loving) is incoherent to begin with. First, an all-loving being must be perfectly just and merciful at the same time, but justice and mercy are oftentimes at odds with one another (sometimes justice requires punishment, which is not merciful). 

Second, the idea of omniscience and omnipotence is incoherent. If a being is all-knowing, it knows what each person will choose before they make the choice, eliminating the possibility of human free will. But if God cannot create humans that can choose to act differently than God foresees, then God is not all-powerful. 

Third, omnipotence alone is contradictory. You can ask the famous question, “Can God create a stone heavy enough that even He cannot lift it?” Or, in another formulation, you could ask, “Can God create a prison so secure that he cannot escape from it?” However you answer these questions, you are placing limits on God’s power.

Fourth, you have the problem of evil, which calls into question the existence of an all-powerful being in light of all of the suffering we witness in the world. This problem was originally formulated by Epicurus, as follows:

“Is God willing to prevent evil, but not able? Then he is not omnipotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Then from whence comes evil? Is he neither able nor willing? Then why call him God?”

It is worth noting that there are only five possible ways out of the problem of evil:

  1. Deny the existence of evil in the world, or, at least, unnecessary evil. (This is a tough position to take, especially in the face of the existence of childhood cancer, for instance.)
  2. Limit God’s power. God may want to reduce suffering, but can’t.
  3. Limit God’s benevolence. Who says that God is all good?
  4. Argue for the necessity of evil for a greater good. (Again, childhood cancer.)
  5. Deny the existence of God.

The fifth option is, of course, the simplest way out of the problem. Atheists are therefore not burdened by the problem of evil, except, of course, in trying to determine how to lessen the amount of suffering in the world. Theists, on the other hand, have their work cut out for them in defending one of the remaining four options. Option four is most likely to be selected, but this option assumes that there is exactly the right amount of suffering in the world—with no examples of gratuitous evil—which is a questionable assumption, to say the least.   

Conclusion

For all of these reasons (and more), it is difficult to find the ontological argument, in any variety, particularly compelling. Any argument for God’s existence using logic alone must always first presuppose the existence of God (circular reasoning) or else utilize the questionable assumption that whatever is logically possible must exist, and that it is possible to think or define things into reality. 

For those that do not already believe in God or belong to any particular religion, the ontological argument is unlikely to make any converts. There are too many weaknesses in the argument, and, as the “devil paradox” shows, an inherent contradiction in the logic. Additionally, defining God as all-powerful opens up that conception to several logical critiques, including the problem of evil and the problem of omnipotence, among others. 

In the next post, we’ll see if the cosmological arguments fare any better. If it is not possible, or at best highly unlikely, that the existence of God can be proven with logic alone, can our understanding of the nature of the universe demonstrate the necessary existence of God as a first cause?

Up next: Medieval Arguments for the Existence of God Part 3: Cosmological Arguments

Further reading

5 thoughts on “Medieval Arguments for the Existence of God Part 2: Ontological Arguments

  1. How respond to the argument that we cannot understand God’s concept of justice or mercy? In my mind that’s falling back on faith and is an argument without substance.

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