Explain how Descartes developed Anselm’s argument that God’s existence is necessary.
Anselm used the Ontological Argument to prove that God’s existence is necessary. The origins of this argument are found in Anselm’s writings, he began with a quotation from a Psalm “The fool says in his heart, ‘there is no God’…” and then reflected on the truthfulness of this. Anselm defined God as ‘that than which nothing greater can be conceived’ assuming you accept this a priori definition Anselm went on to state that anyone who denies God’s existence is a fool. He observed that it is greater to exist in reality than in the mind alone (you would prefer to have a real £20 note than an imaginary one). Someone who doubts God’s existence must have a concept of God in order for them to be able to reject it therefore if the concept of God is the greatest conceivable being then he must exist. He argued that existence was part of perfection, so if God is the greatest being (with all perfections) then it is necessary that he exists otherwise he cannot be the greatest conceivable being and that is not – to Anselm – the definition of God, the very fact that we can conceive of him as the greatest being proves, for Anselm, that he exists. For Anselm someone who denies God’s existence is essentially saying “God, who exists, does not exist”.
Gaunilo responded to Anselm’s argument with ‘On behalf of the fool’. He insisted that if Anselm’s argument is correct it should prove the existence of all other perfect things, he gave the example of a perfect island observing that if someone tried to prove to him the existence of such an island using the same reasoning that it would not mean that the island does in fact exist. Anselm then in response went on to develop his argument further he stuck with his definition of God as the greatest conceivable being and still argued that it was greater to exist in reality than in the mind alone but he went on to ask if it is greater for a being to have contingent existence (meaning existence which can be conceived not to exist) or to have necessary existence (meaning existence which cannot be conceived not to exist). Clearly necessary existence is greater and therefore according to Anselm must be a necessary property of the greatest conceivable
being – God. Necessary existence is only a quality of the greatest conceivable being, so only God must exist, necessary existence is his nature, existence is only a part of the natures of other things (like Islands).
Descartes developed Anselm’s argument that God’s existence is necessary, it is based on the idea that God exists to guarantee what can be known. However, there are a few important differences to note between the argument of Descartes and that of Anselm. Anselm stated that God is the greatest conceivable being and argued that the existence of God is self evident based on intuitive certainty.
Descartes developed this further and aimed to prove God’s existence by using a geometrical example, he argued that God’s existence is as necessary as a shape with three angles having three sides. He pointed out that we do not need to develop complex logical proofs to prove God’s existence just as we do not to prove that the triangle has three sides. Descartes argued that just as the ‘essence’ of the triangle is to have three sides the ‘essence’ of God requires him to exist. As a supremely perfect being the concept of necessary existence cannot be seperated from God.
Descartes built upon many of Anselm’s points in order to argue that God’s existence is necessary. Descartes believed our knowledge of God’s existence is intuitive (similarly to the way that Anselm stated that even the athiest has a concept of God) according to both Descartes and Anselm this intuitive knowledge when analysed is enough to prove God’s existence. Descartes stated that if someone can clearly see that something is intrinsic to the concept of a thing that it must be correct – like the triangle having three sides. There are features that a being or an object must have in order to be that thing. For him these statements are self evident and do not require empirical evidence to prove that they are correct.
Descartes also approached his argument from a different angle. He said that necessary existence is a perfection and therefore the fact that we can concieve of a supremely perfect being proves that a supremely perfect being
must exist as otherwise it would not be supremely perfect. Descartes argued that to suggest that any feature of perfection does not exist in a supremely perfect being is illogical. To deny this in his opinion is the same as denying that a triangle has three sides or that a batchelor is not single. Anselm argued that God is the greatest concieveable being and Descartes also agreed with this point, they both made the assumption that existence is a predicate and a feature of perfection (something that Kant went on to argue against).