The first problem with using a priori arguments to prove god exists rests on the definition of the word god.
Gaunilo was a contemporary of Anselms and opposed Anselms idea of god existing because he is “that than which nothing greater can be conceived”. Gaunilo used the analogy of a lost island, he said just because you can imagine a perfect island does not mean it exists. He claimed that just because you understand what has been said you would be a fool to believe it.
However Anselm refutes this concept as he claims his definition only applies to God. He speaks of god as ‘That than which nothing greater can be conceived”, an island can not be compared to god. Plantinga also refute Gaunilo’s claims because islands have no intrinsic maximum, they can always be improved or bettered.
Immanuel Kant was the philosopher who called this argument the ‘ontological argument. ‘Ontos’ means reality and Kant felt that the arguments jumped from ideas to reality without any real evidence or proof. Kant criticised the ontological argument in his book ‘Critique of Pure Reason’.
He focused on the concept of analytical and synthetic statements, he used these to argue against Anselm.
Analytical statements are similar to a poiri arguments because propositions are true or false depending on the word used, e.g. a female swan is called a Penn. This statement can be proven because if you look it up in the dictionary it will confirm it. These statements tell us nothing new and give us no insight into the real world.
However synthetic statements are similar to a posteriori arguments because they also look for empirical evidence for verification e.g. all lions are omnivores. This can only be verified by observation of lions and therefore gives us insight into the real world.
To say that God is a necessary being is an analytical statement, it tells us nothing of the real world and focuses on concepts rather than evidence.
Kant changes this statement to “If God exists his existence is necessary.” He said that we need actual reasons to say God exists and not a definition of what he might be if he does exist. Kant’s view was that existence is not a predicate (defining quality) and that being able to imagine something does not conclude that it exists.
Bertrand Russell argued against the ontological argument based on the claim that Anselm uses the word exist incorrectly. He claims it is a syllogism, terms that has two common words and leads to a conclusion from that common word e.g. Men exist. Santa Claus is a man. Therefore Santa Claus exists.
He said that existence is and extension to intention, by putting a label on to an object gives it intention, if you can actually see, touch and describe physical aspects of the object then you can say it exists, there for extending the intention.
But a modern version of the argument put forward by Alvin Plantinga is that there are infinite possible worlds, for example in this world I have chosen to study R.E but in another world I may of decided to do history.
Plantinga claimed that there is a possible world where there is a ‘maximal being’ or as Anselm would say ‘that than which nothing greater can be conceived’. But a being that has maximal greatness would certainly have to be present in every world.
‘Maximal excellence’ works along side ‘maximal greatness.’
‘Maximal excellence’ entails omnipotence and omniscience and omnibenevolence.
If ‘maximal excellence’ and ‘maximal greatness’ are entwined then god must exist in our world.
When you consider all of these arguments it is easy to see why some people may consider the argument and others reject it.
The argument has flaws in the fact that it is based on theory rather than fact and that it takes a giant leap of faith.
But it also can not be entirely disproved, for there will always be people who understand what is meant by the term God and their faith is innate.
There will also always be those who do not believe in ‘god’ and for them a sense of God is not enough to prove that his existence is real or necessary.
