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Assessing Descartes' arguments for God's existence


To: Scott B.
From: Geoffrey Klempner
Subject: Assessing Descartes' arguments for God's existence
Date: 11th February 2009 12:40

Dear Scott,

Thank you for your email of 2 February, with your essay in response to the University of London Modern Philosophy question, 'Discuss the strength and weaknesses of Descartes' arguments for the existence of God.'

You have packed a lot into this essay -- in fact I was wondering whether the question might have been, 'Discuss the strengths and weaknesses of one of Descartes' arguments for the existence of God,' giving you a choice. Or perhaps you just decided to change the question in order to give yourself the opportunity to discuss both arguments?

As an essay, this looks a bit rushed. There is some repetition and also unclarity in the structure of the argument. Having said that, you do make a creditable effort to unpack the arguments (more with the argument from perfection to which you have given somewhat more space).

There are some inaccuracies and statements which would raise eyebrows. At one point you say, 'The argument of the idea of God being caused by God is based on the explanation that God must have a cause as nothing comes from nothing. This is based on the Principle of Sufficient Reason meaning that it is self-evident that everything must have a cause.'

The philosopher Leibniz argued for the existence of God on the basis of the principle of sufficient reason. There is also a cosmological argument for the existence of God. But neither of these arguments appears in Descartes. What he does say is that there are constraints on what ideas it is possible to form (the 'principle of adequate reality' which you quote) by virtue of which we may deduce that the idea of God is not formed by mere negation but rather as a result of the action on our minds of that which the idea represents: namely God.

The question asked for the 'strengths' as well as the 'weaknesses' of the two arguments. I agree that it is difficult to find any strengths in the argument from perfection. However, in an exam you would be given credit for at least attempting to say something positive about it. Can you think of anything?

Moving on to the ontological argument, a point to make here is that Descartes assumes that he has an idea of God as a being that possesses all the perfections. How does he know that he has this idea? Could it be that if it really could be shown that we have this idea, then the existence of God can be deduced from his 'essence'?

There have in fact been contemporary attempts to defend the ontological argument. One paper which I mentioned to another of my students yesterday is by Sheffield lecturer Steven Makin, 'The Ontological Argument,' Philosophy. 63 (1988). It is a while since I have looked at this, but I recall that Makin succeeds in presenting a non-implausible version of the ontological argument. At least, it impressed me at the time. My student found the paper quite quickly using the resources at JSTOR.

On the question of whether existence is a predicate, even if one accepts the Fregean view (following Kant's criticisms) that 'exists' is a second-order property of concepts, and not a first-order property of things, it would still be possible to define a property 'exists' (or, if you prefer, 'eggsists' to distinguish it from 'exists' as a second-order property) which every entity possesses, simply by virtue of being an entity. Then saying 'x exists' for any x would be a necessary truth, and 'x does not exist' would be a self-contradiction.

When we say that 'there exists an F', then in Kantian/ Fregean terms what we are saying is that the concept F is instantiated. That is to say, the first-order concept F has the second-order property of instantiation. Whenever the concept F is instantiated, we can therefore say that the object x which instantiates it 'eggsists'. Saying that 'Fred eggsists', for example, would convey the information that Fred belongs to the set of entities which instantiate some concept -- any concept will do: Fred is bald, Fred is a traffic warden, Fred is a giraffe. Any of these statements conveys the fact that Fred eggsists.

Now, in terms of the ontological argument we have a possible concept (or what is claimed to be a possible concept), 'being all-perfect'. Is this instantiated or not? The argument goes, if there is a concept, 'being all perfect' then it must be instantiated, otherwise it wouldn't be the concept that it is. But then again, how do we know that we have such concept, or only delude ourselves into thinking that we have it?

As you can see, it really doesn't make any difference whether we say that 'being all perfect' is (allegedly) a concept which is necessarily instantiated, or say that 'being all perfect' is a concept which is necessarily entails the property 'eggsists' for one and only one x, namely the all-perfect being.

All in all, I can see that you have done a lot of work here and thought hard about the problems. However, you need to organize your thoughts a bit better. Take a bit more time to write a plan and work out what you are going to say before you start your essay. This is good advice in an exam too, even given the time limits. Spending five or even ten minutes planning out your answer to a one hour essay will pay dividends.

All the best,