Descartes - Ontological Argument

Philosophy 11: Introduction to Philosophy The Ontological Argument Simple Version In Meditation 5, Descartes’ argument for the existence of God looks something like this: 1. 2. 3. My idea of God is the idea of a supremely perfect being. Existence is a perfection. Therefore, God exists. It seems at the outset that there is something strange about this argument. This suspicion is confirmed when we realize that a similar argument can prove the existence of a supremely perfect island: 1. 2. 3. I have an idea of a supremely perfect island. Existence is a perfection. Therefore, a supremely perfect island exists. Of course we can run a similar argument for a supremely perfect raisin, a supremely perfect cheeseburger, and so forth. Something must be wrong with Descartes’ argument. Complex Version The ontological argument is notably more intricate than the three steps outlined above might lead you to believe. The crux of the argument is the claim that it is a contradiction to suppose that God does not exist, in the same way that it is a contradiction to suppose that a triangle has five sides. In the case of God, the contradiction arises as follows: if God does not exist, then he is not a supremely perfect being. That is, if God does not exist, we can imagine a being that is more perfect than God. But this a contradiction, since our idea of God is the idea of the most perfect being of all. Therefore, God must exist. This argument takes the form of a reductio ad absurdum. Descartes and Anselm show how the supposition that God does not exist leads to a contradiction, and they then conclude that God must therefore exist. The argument has three premises: p1. God is the supremely perfect being. No more perfect being can be conceived. p2. We can conceive of a supremely perfect being existing in reality. p3. What exists in reality is more perfect than what exists only in conception. From these three premises, the reductio proceeds as follows: 1. 2. 3. 4. Suppose: God does not exist. We can then conceive of a being that is more perfect than God. (p2 and p3) This is a contradiction, since no being more perfect than God can be conceived. (p1) Therefore, God exists. Steps 2 and 3 might be difficult to follow, and so let me try to explain them individually. In step 1 we suppose that God does not exist. According to p2, we can conceive a supremely perfect being existing in reality. And according to p3, such a being would be more perfect than God (since we are supposing that God does not exist). It follows, then, that we can conceive of a being that is more perfect than God. This is step 2 of the argument. In step 3 we arrive at a contradiction, for we have just concluded that we can conceive of a being that is more perfect than God. But p1 states that this is something we cannot do: according to p1, no being more perfect than God can be conceived. Thus, our intermediate conclusion in step 2 of the argument contradicts our first premise, and so we must reject the supposition in step 1. That is, we must reject the supposition that God does not exist. We conclude instead: God exists. The Problem The problem with this argument resides in p1: p1. God is the supremely perfect being. No more perfect being can be conceived. This premise is ambiguous. It could mean one of two things: p1-a. We cannot conceive of a being more perfect than we conceive of God as being. p1-b. We cannot conceive of a being more perfect than God actually is. Look back to steps 2 and 3 of the reductio. We arrive at a contradiction there because—under the hypothesis that God does not exist—we can conceive of a being that is more perfect than God. Here we mean that we can conceive of a being that is more perfect than God actually is. That is, since God does not exist, he is less perfect that this other being we can conceive. After all, what exists in reality is more perfect that what exists only in conception. And so if our intermediate conclusion in step 2 of the reductio is going to contradict p1, p1 must be p1-b. The problem, though, is that p1-b is not acceptable as a premise. Given p3 (namely, that what exists in reality is more perfect that what exists only in conception) we would not accept the premise that we cannot conceive of a being more perfect than God actually is unless we were already convinced that God exists. Thus, if the first premise is actually p1-b, then the argument is valid but question-begging. In other words, the supposition that God does not exist does generate a contradiction, but this contradiction involves a premise that begs the question. pi-b is true only if God exists, and Descartes and Anselm are obviously not entitled to assume that God exists. That is what they are trying to prove! What about p1-a? p1-a is a much better premise. If our idea of God is the idea of a supremely perfect being, p1-a seems to be true. But if p1-a is the first premise, Descartes’ argument is invalid, since the intermediate conclusion in step 2 of the reductio does not contradict p1-a. From the supposition that God does not exist it does not follow that we can conceive of a being more perfect than we conceive of God as being, for we conceive of God as being the supremely perfect being. If there is no contradiction, then there is no need to reject the supposition that God does not exist, and they have proven God’s existence. The ontological argument may have seemed acceptable at first, but only because it slides from one version of p1 to the other. p1-a is an acceptable premise, and that is how p1 is presented at first. In step 3 of the reductio, though, the argument relies on p1-b. Anselm and Descartes construct a seemingly sound argument only by relying on one interpretation of p1 at an early point in the argument and a different interpretation at a later point. If they stick with just one interpretation of p1, though, then the argument is in trouble. If p1-a is the first premise, the argument is invalid. If p1-b is the first premise, the argument begs the question. Either way, they have failed to prove the existence of God.