Descartes and God

Richard Francks considers the relationship between belief and rationality

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Descartes claims he can prove the existence of God. In two or three different ways, in fact. Most people who read those proofs are unimpressed by them. Let’s assume they are right, and that Descartes’ ‘proofs’ give us no good reason to accept his conclusion, that God exists. Let’s go further, and assume that no-one has managed to succeed where Descartes had failed, and produced a different argument which actually does work. The question I want to ask is this: what should we conclude from those failures?

At first the answer may seem obvious. If no-one has given us any good reason to believe in God, then surely we should not believe in God. (We may not actually deny God’s existence – we may try to remain uncommitted on the matter – but still we won’t believe in God.)

That is surely the only reasonable, or rational, response. To do otherwise would be to believe something for which we had no good reason – and that is what it means to be irrational, isn’t it? If I believed for no reason that there was a giant porcupine under my bed, even though I have looked several times and found no trace of it, my belief would be irrational. And so would be a belief in God if I thought all the arguments for such a belief failed.

Interestingly, most people who wrote about such questions in the past have taken exactly the opposite view: they thought that if reason fails to show God’s existence, then, given that God exists, what that shows is the weakness of human reason, which is unable to encompass the great truths of life. Is that an irrational attitude?

If it is, then I think most of us are guilty of similar irrationality. Another task Descartes takes on is to provide a proof of the existence of the material world – he says that although if we try hard enough it is possible for us to doubt it, and to convince ourselves that the world around us is nothing but a dream or an illusion, nevertheless he can show that such doubts are in fact misplaced. Most commentators think that proof, too, fails to do the job. And most contemporary philosophers will also admit that they have no very compelling alternative to it, and therefore that the existence of the material world is something they cannot convincingly prove.

Now ask yourself this question. If you too came to that conclusion, that you could find no good reason to believe in the existence of the material world, how would you react? Would you conclude that, as a rational person, you therefore have no alternative but to give up your belief in matter? Would you cease henceforth to think that human beings (whatever else they may be) are material organisms in a material universe? Or would you do what the great majority of contemporary philosophers do, and simply shrug your shoulders and say it just goes to show that not everything that’s true can (at least at present) be proved?

I suspect most people will take the latter course. So my question becomes: how can it be rational not to believe in God because there is no proof that God exists, if it is also rational to believe in the existence of matter even though we have no proof of it?

Richard Francks retired last year as Senior Lecturer and Director of Undergraduate Studies in Philosophy at the University of Leeds. He has published translations of Leibniz (with Roger Woolhouse), his own Modern Philosophy (Routledge, 2003), and has just finished the manuscript of a Reader’s Guide to Descartes’ Meditations (Continuum, 2008).
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