Critically
assess either the �ideas� or the �ontological� argument for the existence of
God
Does either argument succeed?������������������������ ������� Can they be improved?
Proving the existence of God plays a vital role in Descartes� system. Besides being one of Descartes� prime motivations for writing the Meditations, it is necessary for him to present an omnipotent, non-deceiving being to neutralise the problematic evil demon and to provide a bridge from solipsism to the external world.
Descartes uses two main means to prove the existence of God. The first, nicknamed the �trademark argument�, elaborates on an argument that the idea we all share of a being possessing all perfections, �God�, could only have stemmed from just such an infinite being. This first requires an acceptance of the �causal adequacy principle�, which roughly states that no effect can be greater or more real (where one object is less real than another if it depends on the latter for its existence) than its cause. By extension, the property held by an object which is being thought about will have less objective reality than (and is therefore dependent upon) the formal reality of the property of that object in existence. And so, because the objective reality of our idea of God�s perfections (including existence) must be less than the formal reality of these properties, God must exist.
Later, in the Fifth Meditation, Descartes provides a second argument, known now as the Ontological argument, referring to its similarity to one of Anselm�s five proofs of God. Anselm defined God as being �a being than which nothing greater can be conceived�. He claimed to have self-evidentially proved its existence by demonstrating that if such a being were not to exist, then we would be able to conceive of a greater being just like it which did exist. Showing this argument to be definitely invalid has proved difficult, although it could be said to fall down in a similar way to Descartes�: the fact that we can conceive of a perfect being existing does not rule out that the object of this conception could be tied to the concept of existence without actually existing.
Descartes� argument differs slightly from Anselm�s. It is outlined succintly in the following passage:
�It is quite evident that existence can no more be separated from the essence of God than the fact that its three angles equal two right angles can be separated from the essence of a triangle � It is � a contradiction to think of God (that is, a supremely perfect being) lacking existence (that is, lacking a perfection).�
In other words, existence is a property no perfect being could be without out, and so a perfect being must exist. Critics claim that Descartes has effectively �defined God into existence�.
Interestingly, the ontological argument does not strictly define there to be only one supreme being. Perhaps this is a moot point, since unlike the possibility of there being a thousand consciousnesses all thinking the Cogito, all supreme beings would be identical, since there would be no accidental features to distinguish them.
The essence of the God that Descartes describes as �omnipotent, omniscient, immutable, eternal etc.� is an idea that he holds to be visible to everyone. Descartes� definition of a perfect being then really amounts to �a being which possesses the set of all (positive) properties to an infinite degree�. God is defined in terms of his properties � as indeed, we all are, in each other�s eyes. It is only the Cogito gives our own self a substrate. Amongst this list of perfections, Descartes numbers �existence�. This crucial step hinges on existence being an �essential� perfection in a supreme being, and that �to exist� is simply to �have the property of existing�. So, crucially, Descartes is employing existence as a predicate, a property of an object or name, in this case �God�. He argues this to be part of God�s true and immutable nature, where God is defined as a bundle of properties, one of which is existence, and another is the inseparability of those properties.
Existence is definitely functioning as a predicate in the purely grammatical sense, but it is a more complicated decision regarding whether it is valid to use it in a logical sense. The whole point of predicate over propositional logic is to quantify the instantiations of a property within a domain � it is the purpose of the quantifier to predicate existence. Thus, when symbolised, �x exists� is simply $x. But surely only a being which actually exists would actually have its properties. God would only have the properties of omnipotence and omniscience if he were to exist. When we apply the same test to the property of existence, is anything demonstrated by saying what amounts to �any perfect being which exists has the property of existence�? It tells us nothing.
Descartes was keen to avoid critics extending the ontological argument to objects besides God. He consequently brought in the distinction between �artifical� and �true and immutable natures�, using the right-angled triangle as an example of such a true and immutable nature. His test for an object being true and immutable was to show that even when an object�s essence is known, some of its properties though inherent are not obvious.
This eventually leads to the �overload� problem with the ontological argument. By arguing that existence is a property which can be defined as part of the bundle of properties which make up an object, Descartes opens himself up to various fictional counter-examples: for instance, he contrasts the unity of God�s set of perfections with the idea of a horse with wings, saying that the wings can be separated from the horse. But is this so when we imagine a pegasus � can the wings and the horse still be separated? And in the case of a �superpegasus�, defined as a pegasus which exists � Suddenly, Descartes� argument claims to be able to justify whatever our imagination turns to.
God is seemingly born of Descartes� conception of him. Even if this were true, it requires us to have sufficient knowledge of his essence to be able to proceed with confidence to his existence. Indeed, Aquinas� version of the ontological argument claimed that although God�s existence follows necessarily from his essence, we cannot delineate that essence well enough to see how.
Without God, Descartes cannot progress much further. God is necessary to guarantee the empirical framework of an external world upon which science rests. God is the guarantor of knowledge and memory, and neither the trademark or ontological argument concrete his existence.