We should start with the idea. Descartes has an idea of God, who is “eternal, infinite, omniscient, omnipotent…” If we are to adhere to the Causal Adequacy Principle, then the cause of Descartes idea of God must actually possess all of the features found objectively or representatively in the idea. And as Descartes must admit that he is a finite and imperfect being (as there are many things of which he is ignorant), we must conclude that he, himself, cannot be cause of the idea. Nor does the idea originate from the amalgamation of other ideas, for this would eventually lead to one primary idea, the cause of which must be disseminated in the same way. Thus, he argues, the ultimate cause of his idea of God must possess all of the perfections represented in the idea. From this, Descartes confidently states, “it must necessarily be concluded that God exists.”
But must we simply accept Descartes’ bold assertion that “it must necessarily be concluded that God exists”? And is his argument sufficient to prove the existence of God? I believe that there are some serious objections to Descartes’ method of proof, and find the premise of the Causal Adequacy Principle (which we are seemingly forced to accept as true) to be quite dubious. The first and principle weakness of the Causal Adequacy Principle is its implication of what has been termed by critics as an ‘heirloom view of causation’. That is to say that the only way in which an effect can posses a certain property is to inherit it from its causes. Therefore, there can be no cases of objects being greater than the sum of their parts. But what of the construction of a bridge, for example? The bridge may be very strong when built, and it is built from girders, cables and rivets, the causes of the effects of strength (if we are to follow the Causal Adequacy Principle). But we must agree that although the strength of the girders etc. contribute greatly to the overall strength of the bridge, it is the structure of the bridge (i.e. the way in which the component parts are brought together) which determines its strength. The structure of the bridge is not a property of the girders, the cables or the rivets, but it is the primary source of the bridge’s strength. So this would lead Descartes to argue that the strength of the bridge came from nowhere, as its strength was not a particular property of any of its constituent parts (at least not to the same degree as in the completed bridge). Or we can take Cottingham’s example of the sponge cake. The property of ‘sponginess’ is not present in any of the ingredients (flour, eggs, etc.) but rather is caused by the chemical reactions that take place during the process of baking. So does the ‘sponginess’ of a sponge cake come from nowhere, as Descartes would apparently argue? Or is the Causal Adequacy Principle fundamentally flawed as a premise for an argument to prove the existence of God (or to prove the existence of anything, for that matter)?
And Mersenne’s objection, in the Second Replies, to the application of the Causal Adequacy Principle to the sphere of ‘efficient causation’ provides yet another counter-example. Mersenne considers the causes of life (for animals at least) in light of the Principle. If one takes the efficient causes of life to be the action of the sun and the rain on the earth, then we may conclude that living animals are the effects of non-living causes, leading to the assertion that “an effect may derive from its cause some reality, which is nevertheless not present in the cause.” But Descartes may respond to this with the argument that the Causal Adequacy Principle is based upon the efficient and total cause of an effect. Thus, if animals possess properties that are not found in the sun or rain, then we can conclude that these are not the total causes of animal life. However, simply by denying without substantiation the possibility of genuine emergent properties, Descartes openly contradicts the ongoing (and currently, as well as contemporarily, accepted) notions of evolutionary biology. And although evolutionary biology has yet to be proved as absolutely certain, it is far from being disproved. This issue alone seems sufficient to undermine Descartes’ bold claim of the certainty of the Causal Adequacy Principle being simple “manifest by the natural light”.
I shall now move on to consider Descartes’ second argument for the existence of God, that of the ‘Ontological Argument’. Although the label ‘ontological’ is not Descartes’ (rather it is largely attributable to Kant), it lends to draw distinction between Descartes’ two separate arguments for God’s existence: the causal approach, or ‘trademark argument’ of the Third Meditation and the purely a priori approach of the Fifth Meditation. It is the latter argument that I shall now discuss.
Descartes’ a priori proof bases itself upon the traditional scholastic distinction between essence and existence: that is, what a certain thing is, distinct from whether or not it actually exists. Descartes concurs with the traditional belief that one may consider the essence of a certain thing without having to confront the question of its existence. This a priori proof, he argues, is “at least as certain as any geometrical proof”. The argument is developed through the use of the example of a triangle. Regardless of the existence of the triangle, we may consider its properties, or its essence. The triangles’ “three angles equal two right angles, [and] its greatest side subtends its greatest angle”. Descartes argues that, “these properties are ones which I clearly recognise whether I want to or not, even if I never thought of them at all when I previously imagined the triangle, it follows that they cannot have been invented by me.” So, we may read from this argument that a triangle has a determinate essence and that the essence is independent of the thinker. From this, Descartes makes the step towards the proof of God by the same method:
“It is quite evident that existence can no more be separated from the essence of God that 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).”
So Descartes’ argument for the existence of God is thus. God is defined as a supremely perfect being. This, we may accept, as we may consider the essence of something without necessarily conferring its existence. Secondly, it is claimed that supreme perfection implies existence, the argument being that a totally perfect being must possess all perfections. Along with those previously stated (omnipotence, omniscience, etc.) we must include existence. And on this extraordinarily simple argument, Descartes is able to conclude that God exists.
As seemingly easy as this argument is to construct, it is not easy to accept. Its simplicity belies fundamental contradictions and leads us to important and ultimately decisive objections. Why must we include existence among the other divine perfections? And although we can accept the first premise (that God is a supremely perfect being) as an essence independent from its existence, can this independent essence necessarily entail existence? I shall consider my first objection first. If we must include existence as a perfection, then it must be a property of some sort. But even though Descartes accepts that existence does have properties, there is still no overt reason for it to be characterised as a perfection. 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 by a list 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 purpose of predicate as opposed to propositional logic is to quantify the instantiations of a property within a domain – it is the purpose of the quantifier to predicate existence. But only a being that 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 absolutely nothing.
And what of the contradiction posed by Descartes’ method of proof in this case? He claims to follow the traditional scholastic approach of considering essence as distinct from existence. And it is on these grounds that we may permit him to arrive at his first premise, that God is a ‘supremely perfect being’. This essence can have no objection, because it does not necessarily exist. And then we must accept the second premise, that supreme perfection implies existence - a wholly unsubstantiated premise (as argued above). But the major objection lies in the fact that these two descriptions of God’s essence are used to entail the conclusion of his existence. Not only does this entirely contradict the approach he has used to construct the same very argument, but it also contradicts what Descartes’ terms as his ‘first principles’, the cogito. As, in doing this, he is assuming the premises to be true and certain regardless of their truth.
From the ‘Ontological Argument’ 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, St Thomas 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. And 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. I therefore conclude that neither of Descartes’ arguments for the existence of God are persuasive.
