The Ontological Argument was written about in the book Proslogion by St Thomas Anselm, previous Archbishop of Canterbury in 1093. Anselm never doubted the existence of God and directed his argument towards theists to demonstrate to the people the existence of God as opposed to atheists. Anselm's starting point for the argument came from a passage from the Fool in the Psalm. The Ontological Argument is the only argument that uses reason to justify the belief and that is also an a priori argument as it relies on knowledge gained from reasoning and not from empirical knowledge. Firstly, Anselm's begins by reflecting on a psalm from the Bible which says that ˜Fools say in their hearts, "There is no God ' (Psalms 14: 1). Anselm's reflection to this has become known as the ˜Ontological Argument' “ ontos meaning ˜being' and logos meaning ˜study of'. Anselm developed two Ontological Arguments. The first argument begins with the definition that ˜God is a being than which nothing greater can be conceived'. In the eyes of Anselm, this was a universal definition of God, oblivious to whether someone was an atheist or not. Anselm came to the conclusion that for something to be the ˜greatest thing' it has to not only exist in the mind alone (in intellectu) but in reality (in re) as well because if it just existed in the mind it wouldn't be the ˜greatest thing'. Furthermore, Anselm claims a predicate of God is God's existence. A predicate is an intrinsic property or quality of something. Therefore, if God is a being that than which nothing greater can be conceived, and to exist in reality is greater to exist in the understanding alone, God must, by definition, exist in reality. The idea that exists in reality has the extra property of ˜existence'. Therefore to be the greatest possible thing, God must, necessarily, have his property of existence, thus, God's existence is analytic. That is the logic behind Anselm's first argument.