Image by Stefan Keller from Pixabay

An Indispensability Argument for God’s Existence:

1. Whatever is indispensable in generating some theoretically insightful thought experiments must be admitted into our ontology.
2. A perfect being, or God, is indispensable in the generation of many theoretically insightful thought experiments across multiple disciplines.
3. Therefore, a perfect being must be admitted into our ontology.

I don’t think this argument works because (1) is too strong a claim. There are indispensable entities in many thought experiments, which we don’t admit into our ontologies, like frictionless planes and ideal gases. Nonetheless, those ideas are useful in many thought experiments. But why should they be so useful? I think it is because they substantively entail certain facts were they to actually obtain.

A Modest Indispensability Argument for God’s Existence:

1. Whatever is indispensable in generating some theoretically insightful thought experiments is logically possible (premise).
2. A perfect being, or God, is indispensable in generating some theoretically insightful thought experiments (premise).
3. Therefore, a perfect being is logically possible (From 1,2).
4. If a perfect being is logically possible, then a perfect being exists (by S5, given that a perfect being has necessary existence).
5. Therefore, a perfect being exists (From 3,4).

It seems to me that this argument is sound. An atheist might reject (1), but if something is logically impossible, it is hard to see why it would be theoretically indispensable, since it would entail anything. Impossible entities are, therefore, dispensable, since they function trivially in the thought experiment, and any impossible entity would function in the same way. So one impossible entity is no more indispensable than any other. What’s more, while impossibilities entail anything, we would find ourselves like Buridan’s ass, not directed by the concept itself in any particular way when thinking through the thought experiment. Rather, the direction would be determined by some sort of misapprehension of what a perfect being is–a misapprehension that oddly happens to be shared by every person who grasps the thought experiment. But then it is the “misapprehension” of a perfect being that is functioning indispensably, and we would have to see why it is the case that we are dealing with a misapprehension rather than the concept of a perfect being.

I think the atheist might be more successful in denying (2), by arguing that the idea of a perfect being is not actually integral to many thought experiments. Of course, this places a huge burden on the atheist of wading through thought experiments that make use of a perfect being, so as to demonstrate dispensability. Absent such a demonstration, it seems to me that thought experiments that make use of God do so in a substantive and indispensable manner. For as Voltaire says, “Si Dieu n’existait pas, il faudrait l’inventer” (Epistle to the author of the book, The Three Impostors, 1768). Except, if it is necessary to invent God, then according to my reasoning, God is logically possible, and so actual.

Daniel Vecchio -    https://vexingquestions.wordpress.com/2013/06/02/an-indispensability-argument-for-gods-existence/#comment-3147