Explain the reasoning of the ontological argument as proof of the existence of God. Ontological arguments, by their nature, attempt to prove the existence of God using deductive reasoning to the point of logical necessity. Constructed as a priori proof, Anselm's ontological argument functions from a position of faith in an attempt to strengthen his belief in the existence of God. Anselm asks the question, "Can what I know about God be considered correct?" However, the argument, in some forms, attempts to demonstrate the existence of God reductio ad absurdo. In this essay I will follow Anselm's reasoning along with a discussion of theistic evidence. Stephen Davis argues that a theistic proof must be "informally valid", allowing for arguments. He defined God as “That than which nothing greater can be conceived” (TTWNGCBC). This definition is probably our best way of understanding what God is. Even Thomas Aquinas, who stated that the existence of God is beyond our understanding, could argue that this definition is truer of the existence of God, describing as beyond anything we can imagine. From here Anselm goes on to demonstrate the existence of God on the basis of this definition. There are two types of existence, he states, existence in intellectu (in the mind) and existence in re (in reality). The artist can conceive a painting in intellectu before making his creation an act (in re). From here Anselm argues that existence in re is clearly greater than existence in intellectu. This seems relatively consistent. Surely, if someone offered me the possibility of simply conceiving 1000 pounds, it would be better to actually have it. Just as Anselm looks at the painter, it seems more important that the painting actually exists in the fire rather than remaining in the intellectu. Based on our understanding of God, then (TTWNGCBC), even the “fool” (the atheist) can grasp the concept of a greater being than whom nothing else can be imagined in intellectu. However, since existence in re is greater than pure existence in intellectu, it would be "detrimental to the nature of God", states Lockyer, to exist so as to have standing on behalf of the Fool. Gaunilo argues that just because we can conceive of the perfect 'something' does not mean that it actually exists. As a parody, Ganuilo claims that the idea of ​​a perfect island seems attractive but that does not mean that somewhere in the world the island actually exists. Likewise, if I can imagine the perfect weekend, greater than which no greater weekend can be conceived, it doesn't necessarily exist. While this appears to be a valid criticism, Anselm uses it to strengthen his argument for proof of God's existence. While it is possible to identify with the island, Anselm's "God" is ineffable and as such requires no referent. However, we are left with the possibility that God does not exist (based on our understanding of the island). Therefore Anselm introduces the idea of ​​necessary being and contingent beings. We can all conceive of things that cannot exist (such as humans, life, and everything in the observable universe), and we can conceive of things that cannot not exist (such as the state of affairs and numbers). It is greater that something exists, so it cannot not exist. This idea of ​​necessity pushes Anselm's argument to a state in which God must exist otherwise it would be "harmful to his nature" to have the possibility of contingent things.