Anselm had two arguments in which he develops. The first argument starts off with a definition of God, saying that God is: "A being than which nothing greater can be conceived". Anselm already believes in God and this is significant. He also goes on to say that God is by definition that than which nothing greater can be conceived. This definition is understood by believers and non-believers. Also, it is one thing to exist in the mind alone and another to exist both in the mind and in reality. He then went onto say that it is greater to exist in the mind and in reality then to exist in the mind alone. Therefore God must exist in reality as well as in the mind. If God did not, then we could conceive of one who did and he would be greater than God. Anselm said this is our intuitive understanding of what is meant by the concept of God. In effect, what Anselm is saying is that “God exists” is an analytic statement and we can show that the statement is true merely by analysing what it means to be God. This is called the first form of the ontological argument.
Anselm then decided to prove the type of existence of God and this is the second form of the argument. Anselm begins again by defining God, the same definition as before, and then goes a step further by also describing God as something 'that cannot be thought not to exist'. Anselm says that a necessary being is far greater than a contingent being, which has to depend on something to exist. A contingent being which is dependant, cannot be the greatest conceivable being. He believes this 'necessary existence' quality is unique to the greatest conceivable being and not for anything else with a contingent existence because a contingent being is not the greatest conceivable being that can be thought. For Anselm, God’s reality is inescapable and he is trying to express this in his argument. He is trying to understand more fully what he already believes. This is very different from trying to prove God’s existence to someone who does not accept it.
Rene Descartes (1596-1650) took this argument a little further. He was a supporter of the ontological argument, had to adapt his argument to make it work His version of the argument is some way clearer than that of Anselm. He declared that to say that God does not exist is a logical contradiction. Descartes states that as he has a concept of the most perfect being in his mind, the most perfect being must exist in reality as well. Descartes defined God as a “supremely perfect being”. From this definition, Descartes tried to prove God’s existence because God is a supremely prefect being, He possesses all perfections. The perfect state includes existence, which is perfection in itself. Existence is a predicate of a perfect being. Therefore, Descartes concluded that God exits.
He argues that as he may have the image of a painting in his mind, however it is not as great as the painting when it has been painted. Existence, according to Descartes, is as much a characteristic of God as 180 degrees is a characteristic of a triangle. Just as it is logically impossible to say, ‘that a triangle does not have 180 degrees’, it is also logically impossible to say, ‘God does not exist’. Saying that God does not exist is, according to Descartes, saying, ‘that creature with existence does not exist.’ This is, by definition, an untrue statement, therefore God must, by definition exist.
His main objection was that we cannot know a priori that the idea of God, the idea of infinite and total perfection, is the idea of a possible being. There may not be any disagreement in the idea, but this lack of contradiction is not the same as the existence of possibility. It does not show a contradiction until we have proven a posteriori that God already exists.
Although Descartes does not mention Anselm, and it is unclear whether he was familiar with the “Proslogium”, Descartes’ argument for God’s existence is essentially a modernised version of the Anselm’s argument. Instead of defining God as a being than which nothing greater can be conceived, Descartes defines God simply as “a supremely perfect being.”
Overall, Descartes and Anselm both believe in the existence of God. Descartes tried to prove God’s existence and he believes that because God is a supremely perfect being, He possesses all perfections. Anselm believes that God exists, he is a believer in God and he tries to prove that God exists in his second form of the argument. For Anselm there is no doubt that existence makes a thing more perfect so to say that the most perfect thing must have existence as one of its characteristics is clearly logical. Hence Anselm's agreement with the Psalmist who says, ‘only the fool says in his heart there is no God’. The Ontological Argument claims to arrive at the existence of God by analysing the idea of God and this idea does not depend on experience – it is therefore an a priori argument. Anselm and Descartes expand on this idea and try to prove the existence of God.
