Proving the Existence of God through Rational Deduction of Rene Descartes

By Aiman Reyaz, New Age Islam

September 08, 2013

The French philosopher, scientist and mathematician, Rene Descartes (1596-1650) is considered to be the father of modern philosophy because of several reasons, but the most important of all is his radically new way of thinking which broke away from most of scholasticism ( a mixture of the Aristotelian philosophy with Christian theology). And according to Bertrand Russell, “this had not happened since Aristotle, and is a sign of the new self-confidence that resulted from the progress of science.”

There was no one who could have imagined that doubt could lead to proof- proof of the infinite, perfect Being i.e., God. The question which Descartes is trying to answer is, ‘what can we know with certainty?’ we have, on the one hand, our scholastic tradition (this includes the thought of Aristotle and all the Medieval Christian thinkers and most especially of St Thomas Aquinas) on the other hand we have this new, exciting and “heretic” Galilean, Copernican science. How can we deduce objectively which is right?

The way to do this, according to Descartes, is to find a new foundation, of what some called the “Archimedean point” for all knowledge 2, 3. This point is the hypothetical point from where one can objectively perceive the subject with totality. The expression comes from Archimedes, who said that if given the right size of lever, and standing at the correct point he could lift the earth. Ever since then the notion of this point, this foundation point for all knowledge, has fascinated philosophers, and more especially to Descartes.

So what he hopes is to find some absolute crux of certainty, of which there can be no doubt. He is in search for that something, that foundation where he could base and derive all his knowledge. And the way to do this is- wait for it- try to doubt everything, yes everything. Question everything, doubt everything, think negatively as if nothing exists and see if any belief can’t be doubted 4.

His way of deducing things is very intriguing. He begins by doubting every belief, but he realises that he can’t list all his beliefs. So he categorises them in different branches and doubt each branch. The first thing he does is to ask that he experiences thousands of sense experience and all the “knowledge” which he has, are they genuine or are they dubitable?

For example when we insert a stick in a bucket of water, we see that it “appears” to be bent and when we take it out, it “becomes” straight again. So Descartes says that since my sense experience is not incorrigible, I can doubt it. In other words, what he is saying is that since he can doubt the total efficacy of his sense experience, hence he concludes that they can all be questionable. He is not saying that all of my sense experience is wrong, what he is simply saying is that since some can be wrong, hence all can also be wrong.

After this he turns to more general facts about the world. Like for example: fire is hot, heavy objects fall down etc. These are “facts” i.e., these things happen; but he comes up with a higher level of doubt- he says, ‘what if I am dreaming right now?’ and ‘how can I be so certain that this is the reality?’

His final level is about the logic and mathematics. How can one doubt things like: ‘If men are mortal and if I am a man then I am also mortal’ or ‘a square has four equal sides’ or ’2+2=4’. He is asking now that are these logical and mathematical facts must always be true and can’t be doubted, even if I am wrong about everything else. But then he comes up with his ace, what if, he says, there is an evil genius that is putting these “illusions” in my mind? To stretch it a bit, how do I know that I am not in an alien planet, how do I know that all these “facts” of logic and mathematics are not falsely planted in my mind?

After these beliefs, Descartes now says that he can doubt everything, sense experience, facts of the world and even the logical and mathematical arguments. Now after thinking tirelessly, he finally gets an “Aha” experience and says: “Cogito ergo sum” ( I think, therefore I exist.”) 5 The point that Descartes is trying to make is, even if the mind is being deceived about everything, I still have a mind. If my mind is capable of doubting everything, it proves I have a mind. It is possible that everything, with all the knowledge in my mind can be wrong but still I have a mind.

To say: I doubt my sense experience, I doubt memories, I doubt everything I have known before presumes the truth of ‘I doubt’. Therefore the only conclusion that can be drawn from this is that ‘I’ must exist. This is the starting point!

What does ‘I’ refer to? It refers to ‘res cogitans’ (literally a think that thinks) i.e., non-physical, thinking substance. It only means that my mind exists but it does not mean that my brain exists, which is a physical substance, I can still doubt its existence. Now from this there is a second step: I also know that all the ideas in my mind are indubitable as ideas, not in terms of what they represent about the world but simply as ideas in my mind. In other words, I think I am writing on my laptop; I can doubt that I am writing on my laptop, I can doubt that it is real. But I can’t doubt that I am thinking. Take for example, is the dream real? Yes it is real, what you are seeing is real, but it does not represent the true reality outside the world of mind.

Descartes further elaborates that the essence of material substance if they exist is ‘res extensa’ (literally “extended substance”) i.e., spatial extension. What he is simply saying is the difference between matter and mind (i.e., if matter exists, as he is still doubting it) is that matter is something which takes up space. Mind does not take up space. Our thoughts, our ideas do not take up space.

Now from this he tries to prove the existence of God. And he will try to prove His existence from his mind, which, he has proven, exists. He says that cause of something must be equal to or as great as its effect. Otherwise something would come out of nothing. He says that he has in his mind the idea of God as an infinite, perfect Being. ‘I’, the mind existing by itself, has the idea of God in my mind.7 However, that does not prove the existence of God, I only have the idea that He exists (just as I have the idea that I am writing). But about the “idea” of God in mind, we can ask a very special and important question: How did it get there?

Perhaps this idea of the existence of God came from experience, but nothing in my experience is infinite or perfect. So given that the cause must be as great as its effect, how can an experience of something finite and imperfect thing (i.e., we humans) lead to the idea of infinite, and perfect Being (i.e., God). My mind, which is finite and imperfect could not create or imagine this idea of God, who is infinite and perfect. So the only option left is that it must be the case that the idea of God is innate in my mind. In other words, it was placed in my mind when my mind was created and it could only be caused by a Being that is really infinite and perfect. So, there must be a God, an infinite, perfect Being in reality, independent of my mind in order to put in my mind the idea of God. This is his proof for the existence of God.

Now very briefly let me say about the sense experience, facts of the world and logical and mathematical arguments. First of all, Descartes says, that I exist, and God has to be there to put the idea of God in my mind and if all my sense experience, facts of the world and logical and mathematical arguments are wrong, then that would make God a deceiver. I can make errors in judging the sense experience, my judgement can be wrong, which is my imperfection. However if all the best faculties (like scientific analysis, logical and mathematical arguments) also lead to the same conclusion that my sense experience is wrong, then in that case God is responsible for this imperfection. But since God is perfect and infinite, He cannot deceive. Therefore the errors that I would make would be of my own accord and God cannot be held responsible for it.

One of the biggest problems which Descartes left us with is how can my mind, which is a non-spatial thing affect my body, which is a spatial thing and vice verse? He was criticised because of his foundationalism i.e., the attempt to give a correct, presupposition less ground for objective or realist knowledge claims. Descartes used A to prove B and from B to prove A.

1.       History of Western Philosophy, Bertrand Russell, Pg 511

2.       http://en.wikipedia.org/wiki/Archimedean_point

3.       http://www.rep.routledge.com/article/DA026SECT5

4.       The Age of Reason Begins, Philosophy Reborn pg 642

5.       Principles of Philosophy, 1644

6.       The Shorter Routledge Encyclopedia of Philosophy, Edward Craig.

7.       The Big Questions, Robert C. Solomon, Kathleen M. Higgins (8th edition)

8.       An Illustrated Brief History of Western Philosophy, Anthony Kenny. (Blackwell Publishing)

URL: https://newageislam.com/islamic-ideology/proving-existence-god-rational-deduction/d/13408