To make this leap however, Descartes has first to prove essence and existence to be inextricably linked. He argues that a triangle’s properties and its essence cannot be separated and thus when he conceives of a perfect being it must exist for if not it would be less than perfect. Yet in itself Descartes concedes that this is not enough for if he were to consider a winged horse it does not follow that such a being exists. The key point is that God, a perfect being, and His existence are inseparable. Although Descartes can conceive of a horse with or without wings, he can only conceive of God as existing. His thought imposes no necessity on His existence, rather the necessity of the concept itself leaves Descartes unable to conceive of anything else.
At this point Descartes strays from the ontological argument to the proof of innate ideas, and the power of clear and distinct perceptions. God is in his view the most self-evident innate fact we posses, and from this stem all our other certainties. His benevolence, argued by Descartes in previous Meditations, can be relied upon to guarantee our memories of concepts clearly and distinctly perceived in the past. Thus “the certainty and truth of all knowledge depends uniquely on my awareness of the true God”, allowing Descartes to move onto the proof in later Meditations of the corporeal world.
Kant forcefully criticised Descartes logic and conclusions arguing that the proof of God could lead to proof of anything. By ascribing any object the inherent quality of existence it follows from Descartes that such a thing exists. If for instance a triangle were said to be inherently existent then the statement “a triangle does not exist” would be self-contradictory and leave us with a proof of the triangle’s existence. Descartes reply would be based on God’s unique perfection and the inability to separate existence from the rest of his perfections. Kant goes on to argue that “God does not exist” is contradictory, but “there is no God” is not, for in the latter we are rejecting the predicate along with the subject. Another criticism of Kant’s is that “exists” is not really a predicate at all and as such cannot be a kind of perfection we may posses. It is instead, in Kant’s view, what the existential quantifier captures and as such cannot be lumped with other qualities under the perfection umbrella. Such a view would leave the ontological argument deeply flawed and such assumptions as God’s unity of essence and existence would no longer follow.
Gassendi made similar criticisms as others when arguing that by identifying a God we are unjustifiably assuming his existence. This misses Descartes view of God as a pure object beyond being and non-being, capable of properties regardless of its existence. His existence comes from the real predicate “is supremely perfect”. By defining God as a pure object Descartes can avoid the accusation that his logic could prove anything in another way to that already discussed; by identifying an object and then questioning its existence, only an affirmation of its existence avoids a contradiction.
Hume argued that the existence of an object was no different from the idea of an object for considering an idea to exists, he reasoned, was no movement forward. The idea of something existing is the same as the idea in his view. The key defence from Descartes was to acknowledge that we never think of things as “without thinking of them as existents”. Rather they might contain possible existence as opposed to the necessary existence of God. If we can conceive of a thing then we know it is possible that it exists, but in the case of God we know that it is necessary for God to exist.
This necessary existence comes from two sources, firstly existence as perfection and God’s own perfection make His existence necessary. The second source is more complex and stems from God’s omnipotence. The clear and distinct idea of a God allows initially for possible existence. God’s inherent independent all-powerful qualities then lead Descartes to feel that if he exists at all it is by his own power. Because everything wants to exist, and anything that can and wants to do something will, we can conclude that God does exist according to Descartes. This splitting of necessary and possible existence is an important tool in the defence of Descartes Allowing this existence of God to be proved using rules applicable only to this situation. But is still contains weak points. For instance, there is a lack of proof for the assumption that all beings want to exist.
Similar thinkers such as Meinong can also provide support for Descartes in response to criticism from writers such as Russell. Meinong saw necessary or possible existence in everything. The possible existence of a triangle is in the perfection of the triangle just as with God and His necessary existence. The issue then of self-contradictions is also dealt with because they arise purely in our minds. It is only the mistaken connections our mind makes that causes self-contradictions for they cannot exists outside the mind else they would be non contradictory. Russell also argued that if existence is a predicate then anything we conceive must exist. This was line of argument refuted by Descartes because it ignored the required true and immutable essence of a thing which has necessary existence, i.e. it is not a pure object. The exact criteria of these pure objects remain a mystery and are a significant weakness in the theory, except where they concern God for his unique omnipotent and all-perfect nature is perhaps the definition of a pure object.
The ontological argument has some very important conclusions and can be supported by two important supplementary ideas. The distinction between necessary and possible existence combined with the concept of pure objects can answer many of the critical questions. But there is an important hole in Descartes’ theory that is left by the argument. If what does not exist cannot have any properties than the cogito and Descartes own existence is provable. And if what does not exist can have properties then God may exist and the ontological argument is valid. But these two appear incompatible, an issue Descartes did not address leaving his philosophy to appear dangerously inconsistent.
