This prayer was called the proslogion and tried to prove God by means of reductio ad absurdum, which states that the existence of God is logically necessary. The argument is based on the word “God”, a being that possesses all perfections, therefore must exist. Anselm was aware that the existence of God is denied by atheists and in response to this, he states “the fool has said in his heart there is no God”. Descartes later reformulated the ontological argument, who sought to prove the existence of God through reason alone.
He stated that he exists, and in his mind he has the concept of a perfect being, and as an imperfect being, he could not have conjured up the idea of a perfect being, therefore this idea must have originated from the perfect being itself, and this perfect being must exist in order to be perfect, consequently a perfect being exists. He also stated that the idea of God is the idea of a perfect being, and a supremely perfect being has all perfections, existence is perfection, a supremely perfect being must have existence, therefore it is impossible to think of God as not existing, hence God exists.
Gaunilo stated that if the ontological argument was applied to things other than God, then it led to invalid conclusions. He applied Anselm’s premise to the idea of a perfect island: I can conceive of an island that no greater island can be thought of; such an island must possess all perfections; existence is a perfection; the island exists. He also stated that the views of the “greatest island” would be subjective. Kant stated that “existence is not a predicate”, which would flaw both Anselm and Descartes arguments.
He observed that existence is not associate with the definition of something since it does not add to our understanding of that thing; “it would be self-contradictory to posit a triangle, yet reject its three angles”. Russell furthered Kant’s idea, and stated that we should consider the claims that all cows have tails and all unicorns have horns. Grammatically, this is correct, however, it does not state whether they exist, and therefore does not provide explicit information. Similarly, Hume stated that the argument makes false assumptions about existence; “we cannot define something into existence”.