Cartesian scepticism and the ontological argument for God’s existence

John asked:

In Meditation I, Descartes describes a kind of powerful doubt that prevents him from being persuaded of the truth of almost anything. Is Descartes’ doubt powerful enough to stop Anselm’s ontological proof from being convincing?

Answer by Tony Fahey

Hi John, let us begin by considering, briefly, both Anselm’s and Descartes’ approach to this issue: Anselm’s argument for the existence of God can be found in chapters two and three of his Proslogion. Very roughly, his argument goes like this: God is the most perfect being; it is more perfect to exist than not to exist; therefore god exists. It should be said that Anselm was a monk and bishop of Canterbury who held that faith is prior to and provides the context for understanding. Thus, for Anselm, it is not the case that we understand first in order to believe, rather it is that we believe in order to understand. According to Anselm, if God is defined as a being than which nothing greater can be conceived or thought, then God must exist, since it is greater to exist in reality than just in the mind as notional or conceptual.

Like Anselm, Descartes believed that each of us possesses the idea of a perfect entity. Inherent in that idea is the fact that a perfect entity must exist – because, as Anselm had said, a perfect entity can only be perfect if it has existence. Neither could we conceive of a perfect entity if there was no such thing. We are imperfect, said Descartes, so the idea of perfection cannot come from us. Descartes reasons that the idea of a perfect being must have been placed in him by a really existing perfect being – God. That God exists was therefore as self-evident to Descartes as that a thinking being must exist.

One of the earliest critics of Anselm’s ontological proof was his contemporary Gaunilo (also a monk), who, in his Liber pro Insipiente, opposed it on the grounds that humans cannot pass from intellect to reality. According to Gaunilo, Anselm’s argument would imply that anything, no matter how fictitious or chimerical, which was thought in the mind, would have to exist in reality. To prove his point Gaunilo uses the example of an ‘island more blessed than any other, a perfect island… greater than which nothing greater can be conceived’. Given Anselm’s ‘proof’, he argues, if one can conceive of such an island in this way, then it follows that such an island must exist in reality as well as in the mind – this, of course is absurd. In fairness to Anselm, where he attempted to defend himself from Gaunilo’s criticism by saying that his concept of a priori perfection applied specifically and only to God, Descartes decided that since he could conceive God as a ‘clear and distinct’ a priori idea that any such ‘clear and distinct’ idea should be granted the same unquestionable status.

Thus, we can see that since Descartes sets out on his epistemological journey by doubting everything, it may seem, initially, that his doubting would have been powerful enough, if not to actually ‘stop’ Anselm’s proof from bring convincing, to at least put it on hold (as Husserl might say, ‘to eschew it’) until it could be shown to be either valid or invalid. However, because it can be shown that both Anselm’s and Descartes’ theses make the same case in regard to the proof of the existence of God, it must be argued that Gaunilo’s critique of Anselm equally applies to Descartes.

Indeed, it can further be said that when Giambattista Vico, in his critique of Descartes’ proof of the existence of God, says that those who seek God in this way do so out of stupidity. Adding that in order to know that God exists, one would have to know the genus and mode of God – that is, one would have to be the maker of God; and that those who attempt to prove the existence of God a priori, are guilty of impious curiosity, one might be forgiven for thinking that amongst the ‘those’ Vico speaks of, one could be forgiven for thinking that he may well have been counting Anselm.

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