The Ontological Argument holds much of its strength in its own properties of being a deductive and logical priori argument working with the , as Descartes suggests innate definition of God and his qualities. However this strength also plays into its greatest weakness through, as Karl Barth criticised of all arguments made in intellectu rather than from revelation through Jesus Christ, is that it comes from a mind that is inherently varied, corruptible, and does not always provide a valid basis for reason.
Guanilo appeals to us the fact that this deductive form of thinking found in the Ontological Argument can be applied to anything that could exist, such as a perfect island, that which Anselm would say would create the property of existence simply from its definition of perfection in the human mind. The Saint replied to this criticism with the idea that as God is a necessary being; compared to the contingency of an Island that relies on geography and the biology found there, God is viewed as something necessary that does not rely on other beings, therefore the ontological argument cannot be applied to anything, which would obviously be impossible.
However, the property of necessity is not limited to our classical christian God, many cultures view their own God as “That than which nothing greater can be conceived” and therefore should all be able to follow the same logic as Saint Anselm as a theodicy for their own monotheistic God, this would be unacceptable for a propositionalist and for example would break the Muslim Shahada which states there is “No God but God”, though modern theology is often following a more interpretive view of faith that would allow for different understandings of God through different religion, it still shows a major flaw as a proof for a God for many believers.
A second criticism by believers comes from the opposition of needing a “proof of God’s Existence.”, especially one that comes from the human mind.Whilst Aquinus claimed the flaw lies in God’s extra-natural origin, an existence that B. Davies believes cannot be proved by analysing a real concept, voluntarist Christian Karl Barth believed that as more proof for God is used, less faith is needed so the belief is weaker, this follows Hick’s idea of a perfect epistemic distance for faith where we have an equal chance of God’s existence and non existence, Kierkegaard would agree that a greater risk of God’s existence would lead to greater faith. Buber adds to this by stating that we cannot analyse our faith with God as it changes our relationship form an “I-thou” to “I-It” where God is considered an item, and so is not representative of true God. However this does not apply to all voluntarist ideas, a person following Pascal’s wager would be completely in favour of a “proof of God’s existence” as it would increase the win rate of their game, whist non-voluntarists such as William Clifford would state that to make a decision without sufficient reason is immoral, we can see a modern day example that also shows the weakness in Pascal’s wager with fundamental Islamic Jihadism where some would say proof of God, and more importantly his instructions to us, is taken without reason and leads to a worse and more immoral fate than that which would have been created with a more skeptical agnosticism.
Followers of the Ontological argument however would say this ignores a core value of the theodicy in that we have proof for God through the fact that God’s existence is self evident without external measurement as, put by Descartes, that God cannot be separated from existence just as how three angles cannot be separated from the idea of a triangle. Although this attempts to diminish the role of empirical evidence it is not satisfactory for many thinkers.
To conclude, as a rationalist the argument has a strong basis in which much of the issues can be resolved through greater theological thinking on God’s properties, such as how God is a necessary being with whom we share an I-Thou relationship, and through modern ideas such as a globalised spiritualism interpreted as God, although many would passionately seek to distance themselves from this line of theology. However not only can voluntarist believers reject the priori argument, but actively resent it as an attack on faith through our attempt to “prove” God with our fallen minds, added to this, an Empiricist would see the argument as flawed in finding a synthetic existence through worldly means. Overall the ontological argument makes a stronger case for why we might find ourselves believing in God than as an outright proof of their existence.