Wolfhart Pannenberg on Descartes's ontological argument
Descartes’s arguments for God are not the most popular, I suspect this is partially due to Descartes generally being unpopular in contemporary philosophy and often playing the role of a kind of whipping boy by those who oppose substance dualism or the mechanistic philosophy. Nevertheless, Wolfhart Pannenberg, in his systematic theology volume 1, defends Descartes’s ontological argument and uses it in a way that I find attractive. The argument, as I understand it, is rather similar to Hegel’s ontological argument which is also not all that popular in philosophical theology, I suspect due to its not being laid out in an explicit way by Hegel and being somewhat dependent on his larger metaphysical system. Here is Wolfhart Pannenberg’s defense of Descartes’s ontological argument:
In his thinking about God's infinity Descartes also went further than Duns Scotus by expressly basing the thought of God, like Gregory of Nyssa, on the idea of the infinite, and not deriving what he had to say about God's essence from the idea of God as the first cause. Latin Scholasticism no longer realized that Gregory's rejection of the latter course was connected with his opposition to the Arian view of God. Descartes arrived at a similar rejection by a different route. He mistrusted the traditional argument of philosophical theology because it had to rely on the thesis that infinite regress in the causal sequence is impossible. But Occam had already shaken this type of argument, showing that it is of very limited cogency. Occam among others did not think that we can convincingly infer God's infinity from his being the first cause. Descartes now discovered a wholly new way of asserting God's infinity. From the intuition of the infinite as the condition of all ideas of finite things he moved on to the thought of God by way of the idea of perfection that is contained in the intuition. The absolute superiority of the divine being and the idea of God as a necessary being also seemed to him to be posited herewith, so that he was able to revive the ontological argument by deriving the thesis of God's existence from the concept of his essence.The argument of Descartes has been subjected to the persistent misunderstanding that the certainty of the cogito is the basis of the proof. Descartes bears some responsibility for the misunderstanding, for in the Third Meditation he first introduces the thought of God as one of the ideas present in the mind. But he also says expressly that the idea of the infinite is the condition of every idea of finite things, including the Ego (cf. Med. Ill, 28). Thus the thought of the I in the cogito rests on the view of the infinite, for like all finite things it can be formed only by limitation of the infinite. Hence the cogito sum presupposes the thought of the infinite instead of being its basis. The common idea in the history of modern philosophy that Descartes is the founder of epistemological subjectivism is thus mistaken. It ascribes to Descartes a view which Locke pioneered and Kant developed. Descartes did not make a sure subjectivity which is independent of the thought of God the basis of certainty about the existence of God. Instead, he was close to the tradition of so-called ontologism39 that goes back to Augustine and that makes intuition of God the basis of all other knowledge. The Meditations begin with the cogito, but this does not mean that it is the material basis of all that follows. It simply serves to introduce Descartes' fundamental thesis that the infinite is the condition of the definition of all finite things. The cogito sum simply adopts an argument of Augustine against radical skepticism,40 while basing the thought of God on the primacy of the infinite for the knowledge and being of everything finite develops an argument which helps us to understand Descartes' claim to originality.
With its revival of the ontological argument Descartes' grounding of philosophical theology seems to me to have reversed the traditional order of the questions whether God is and what he is. The idea of God as infinite and perfect being comes first and existence follows from it. In this regard Jungel cleverly remarks that in Descartes humans set themselves between God's essence and existence, and the concept of God is thus shattered.41 This would be true if the certainty of the cogito were independent of the concept of God and the basis of its discussion. Then it would indeed depend upon human judgment whether the essence of God, which is first posited merely as an idea in the human mind, has reality in the sense of existence outside us or not. The argument of Descartes, however, is the opposite one that the idea of God as the idea of the infinite is the condition of the conceivability of everything finite, including the Ego itself, and that it has the basis of its existence in itself. It we take that seriously Jungel's criticism loses its point.
Nor does Kant's criticism of the ontological argument touch the basis of Descartes' revision of the philosophical doctrine of God. It does not relate to Descartes but to discussion of the ontological argument in the 18th century, in which Descartes' idea of the infinite as the primum cognitum no longer played a part. This idea had been replaced by that of the most real being, which Kant called a transcendental ideal of reason because underlying it is the epitome of all positive predicates in the defining of individual things by the assigning or denying of specific predicates. The idea of the individual thing is thus formed by limitation of the epitome of all reality. To this extent the thought of the transcendental ideal in Kant has the same function as that of the infinite in Descartes. But in Kant the transcendental ideal is no longer a condition of the knowledge of things, including the thought of the Ego, but is simply a concluding thought which like all other rational ideas has as its content an understanding of the use of reason and its conditions.
Kant knew very well that we can conceive of things in time and space only as a limitation of the infinite totality of time and space as we see it. But he did not discuss the relation of this fact to the idea of a most real being as it is established in Descartes' thesis that the idea of the infinite is the condition of all experience of the finite. If Kant had noticed the relation between these themes he would have come up against the question whether the thought of God is not the condition rather than the conclusion of the idea of all finite things.42 Thus the Critique of Pure Reason had the argument of the Third Meditation in view but did not fully meet it. The line of thinking in the transcendental aesthetics presupposed Descartes' basic assertion but did not draw out the theological implications.
Wolfhart Pannenberg, Systematic Theology Vol. 1, 350 – 353