(1) Suppose (with the fool) that God exists in the understanding alone.
(2) Given our definition, this means that a being than which none greater can be conceived exists in the understanding alone.
(3) But this being can be conceived to exist in reality. That is, we can conceive of a circumstance in which theism is true, even if we do not believe that it actually obtains.
(4) But it is greater for a thing to exist in reality than for it to exist in the understanding alone.
(5) Hence we seem forced to conclude that a being than which none greater can be conceived can be conceived to be greater than it is.
(6) But that is absurd.
(7) So (1) must be false. God must exist in reality as well as in the understanding.
This reading of the argument is amply confirmed by the final statement:
“Therefore, if that than which nothing greater can be conceived exists in the understanding alone, the very being than which nothing greater can be conceived is one than which a greater can be conceived. But obviously this is impossible. Hence there is no doubt that there exists a being than which nothing greater can be conceived, and it exists both in the understanding and in reality.”
A philosophical proof is an argument based on a set of true premises and that is what the ontological argument appears to be. The ontological argument does fail as a proof of God’s existence for a number of reasons, for example, in the second for of the argument it does not come to a conclusion and therefore cannot be a proof. There have been advocates that have tried to defend the argument and say that it is an acceptable proof for the existence of God.
Anselm, Archbishop of Canterbury was the man who postulated the ontological argument, although he never meant to as it was a prayer that was designed to strengthen a believer’s belief in the existence of God. Anselm describes God as “A being which nothing greater can be conceived.” he says that even an atheist can accept this definition and so this being must exist as a concept in our mind. Anselm then goes on to argue that it is better to exist in both the mind and in reality. From this Anselm concludes that God must exist both as a concept in our minds and also in reality or he would not be the greatest conceivable being.
A French monk named Gaunilo was the first to refute the ontological argument. Gaunilo said that Anselm’s reasoning was absurd when it was applied to other fields. Gaunilo gave the example of “a most perfect island.” he argued that this island that would be most perfect would have to exist in reality if we were to follow the reasoning of Anselm and says that it would be impossible to prove the existence of such an island. However, Anselm relied to Gaunilo with a justified and seemingly tight argument. Anselm argued that his reasoning could only apply to God, as only God was infinite and unique. Anselm said that it was impossible to have a perfect finite thing in existence because we could always postulate something better than it. Anselm concluded that only God was perfect and everything else fell short of perfection so the ontological argument only applies to God. This attempt to weaken the argument appears to fail and shows the argument to be strong.
In the 17th century Renes Descartes reformulated Anselm’s first form of the ontological argument in his book “Meditations” Descartes postulated a “supremely perfect being” Descartes main contribution to the ontological argument was that of treating existence as a predicate that is a good thing to have. He concluded if existence is a predicate then it was surely better to have than to lack it and that if this was true then God must posses existence as a predicate and therefore exist. Descartes used and example of triangles saying that if a triangles angles add to 180 degrees as that is what is included in the definition of a triangle, so he argues that God must have existence as a characteristic of himself.
Descartes argument brought with it many criticisms, Gassendi was the first to say that existence was not a property but was something else. He argued that a being without existence would not be imperfect; the being would be nothing as it would not exist. This led the way to very damaging criticisms of the argument, which would make it hard to become a proof.
Kant agreed that in theory perfection would include existence, as it would be contradictory to say otherwise, however, this does not prove Gods existence. Kant argued that we could reject the concept of an all-perfect being along with the idea of it possessing existence just as we can reject the concept of a triangle including the idea of its angles. Kant also rejected the idea of existence being a predicate that one can own. He gave an example of $100. He argues that there is no difference between the real and the imaginary $100 apart from the real one existing. Existence adds nothing to the concept of the $100 it is the same. This appears to be a strong attack on the argument and stops it being a proof as the argument relies on this premise being accepted.
Russell gave a 20th century version of Kant’s argument. He argued if we were to say cows exist but unicorns do not we do not mean that cows posses the attribute of existence, the concept of a cow exists in reality, while the concept of a unicorn has no instances in reality and this again is a powerful argument against the ontological argument being a proof.
The second form of the argument tries to prove that God is a necessary being and that he exists necessarily. That is, God either exists or will always exist, or he does not exist and never will exist. Anselm argued in his second form that we can imagine the Greatest Conceivable being existing without it having a cause and that if it doesn’t exist we can’t imagine it existing as it would have to have a beginning. But because we can imagine it existing then it must exist.
This argument on the outset appears to be strong; however, it has its flaws. First, the argument relies on us acknowledging the God is the greatest conceivable being and that the it posses necessary existence. Second, even if we do accept the premises the argument still fails because the greatest conceivable being could be a being that can be imagined to exist but does not currently exist. Finally, the main error with the argument is that the fact that we can imagine the greatest conceivable being does not prove that it cannot not exist.
Norman Malcolm gave a 20th century version of the second form. In it he argues 7 steps which take him from “God can neither begin to exist or cease to exist” to step 6-7 “God’s existence is possible therefore God’s existence is necessary.” The weakness with his argument, the weakness that causes it to fail is step 6 which is very suspicious and an atheist could argue with justification that God’s existence was impossible. This prevents this version being a proof. Malcolm does not believe that the ontological argument is persuasive in itself. He believes that some other insights are required from within human experience, such as a sense of the passing nature of all contingent things, before a person can understand the insights of religious faith.
In a different vein D.Z. Philips supports the ontological argument for its logical clarification of the concept of God. He accepts that Anselm was attempting to express what he already believed. His argument is that, God is unlike all contingent things, and is not part of any class or kind. The key to the argument according to Philips, is in the way Anselm expresses the unique sense of the word God. The word has a unique ‘grammar’, and it is therefore a mistake to even say ‘God exists’ in any ordinary sense. God does not ‘exist’ alongside other existing beings, Philips refers to this as non-realism. Philips argues that a call for a profound level of understanding that only faith can provide proves Gods existence.
In conclusion, the ontological arguments in both of its forms fail as proofs of Gods existence. In both forms there are many criticisms that damage the argument and restrict its success, for example Anselm’s first form is dependent on us accepting Anslem's definition of the greatest conceivable being. In the second form the argument fails to reach a conclusion and only leaves us with the possibility of the greatest conceivable being existing therefore it fails as a proof that God is this being.