Question: Richard wrote me a while back asking about Peter van Inwagen’s critique of ontological arguments—specifically, his critique against modal versions of the ontological argument. Since I don’t have the text of Richard’s question, I am just summarizing the issue. Basically, van Inwagen states that the crucial step in modal ontological arguments (that it’s possible that a maximally great being [MGB] exists) trades on an ambiguity of premises. It is epistemically possible, for all we know, that MGB exists. However, what modal ontological arguments (MOA’s) need is for MGB to possibly exist in the metaphysical sense. Van Inwagen claims our modal intuitions simply aren’t of the sort needed to establish this metaphysical possibility, and so, as an argument, MOA’s can’t even get off the ground. What can be said about this?
Response: This is an interesting situation, since van Inwagen is a Christian theist. Thus, he has great sympathy for the overall situation in which the proponent of the MOA finds herself. As a result, this isn’t some atheistic philosopher looking for any excuse to avoid a God. Moreover, Peter van Inwagen is a highly respected philosopher, so it is also worthwhile to take what he says seriously. That being said, I do not think the case is so simple as he would have us believe.
The first, and primary, criticism that I would have of this criticism of MOA’s is best expressed by a paraphrase of what a professor once told me. “We use our modal intuitions all the time, in everyday circumstances. Why only now, at the question of God, do we abandon them, or say they are not reliable guides to truth?” Let me explain. The main and pivotal premise of the MOA is something like: “It is possible that a MGB exists.” The critic says he’s not sure how one can know this. The response is that we use our modal intuitions. What are those? An intuition, in this case, is not like a feeling or a sixth sense. Instead, it’s more like what we call “rational intuition,” or how one knows laws of logic and reasoning, mathematical truths, and even metaphysical and moral claims. What do I mean by “modal”? Modal logic and reasoning covers different modes of existence: necessary and possible (or contingent). When one claims that she has a modal intuition, then, she is claiming that she rationally perceives that something is metaphysically possible.
Let’s go through some examples. First, she can intuit that things are impossible. Consider the idea of a married bachelor. Her rational, modal intuition tells her that this is an impossible state of affairs. Then, consider the 50th President of the United States. Even though, if she is reflecting at this present time, there is no such referent, it is still metaphysically possible that there be one, eventually. Finally, consider something that never actually exists, like a unicorn, and she can have some kind of modal intuition about that, upon reflection.
The point is that these modal intuitions are not merely saying, “For all we know, this is the case.” They are rather purporting to be real guides to the possibilities of reality. And what reason do we have for saying that none of the examples above are justifiable? Perhaps it will be objected that God is not like any of those other examples. “For the MGB,” they may say, “is a necessarily existing thing. And how could you intuit a thing like that?!” It is true that an MGB entails the property of necessary existence. But why think that in order to modally intuit that something is possible one must know all properties of that thing? Most everyone agrees that every source of knowledge is at least potentially defeasible; that is to say, one’s rational or modal intuition is still subject to defeaters, so that if he has good enough reason to think that one of MGB’s entailments is impossible, he can go back and override his belief formed through modal intuition. Basically, I see only good reasons for accepting our modal intuitions.
But what if the skeptic decides that, although he intuits the modal possibility of MGB, he rejects the premise because he thinks MGB is impossible? This is fine, but he has to hold the impossibility of MGB stronger than he holds his modal intuition about MGB’s metaphysical possibility. Otherwise, he’s just engaging in question-begging against the argument. There seems to be quite good and normal reason to accept modal intuitions, and no good reason that would rule it out a priori.