The Reverse Ontological Argument

by Max Andrews

Interestingly, there is an argument used by atheists to demonstrate that God is impossible, which picks up on the ontological argument. This argument is traditionally called the reverse ontological argument. Instead of demonstrating that God a maximally great being that exists necessarily, the reverse form is used to demonstrate that God is impossible. To give a context for the atheistic argument here are the two most popular versions of the theistic ontological argument:

The Anselmian Ontological Argument (Theistic)

  1. God exists in the understanding
  2. God is a possible being
  3. If X exists only in the understanding and is a possible being, then X might have been greater
  4. Suppose God exists only in the understanding
  5. God might have been greater (2, 4, 3)
  6. God is a being than which a greater is not possible
  7. So, a being than which nothing greater is not possible is a being which is greater is possible
  8. Since 4 led to a contradiction 4 must be false
  9. God exists not only in the understanding alone—God exists in reality as well
    • Existence in reality is a great making property
    • The argument is a reductio ad absurdum. To prove X assume ~X.  Show how ~X leads to a contradiction or patent falsehood.

The Plantigan [Modal] Ontological Argument (Theistic)

  1. The property of being maximally great is exemplified in some possible world.
  2. The property of being maximally great is equivalent, by definition, to the property of being maximally excellent in every possible world.
  3. The property of being maximally excellent entails the properties of omniscience, omnipotence, and moral perfection.
  4. A universal property is one that is exemplified in every possible world or none.
  5. Any property that is equivalent to some property that holds in every possible world is a universal property.
  6. Therefore, there exists a being that is essentially omniscient, omnipotent, and morally perfect (God).

The Reverse Ontological Argument (Atheistic)

  1. It is possible that God (MGB) does not exist.
  2. If it is possible that God doesn’t exist, then God doesn’t exist in some possible worlds.
  3. If God doesn’t exist in some possible worlds, then God doesn’t exist in all possible worlds.
  4. If God doesn’t exist in all possible worlds then God doesn’t exist in the actual world.
  5. If God doesn’t exist in the actual world the God does not exist.

The problem is in premise two–MGB must be demonstrated to be incoherent. Now, when the atheist is defending the argument he may certainly attempt to demonstrate that a MGB is incoherent but that’s the task before him. There certainly isn’t an explicit contradiction so an implicit contradiction must be explicated. This goes back to premise 1 of the theistic ontological argument while not dealing with the criticisms needed to justify premises one and two. It must be demonstrated that God is logically absurd before finishing premise one. All the theist must do is defend the case that God’s essence (and indexed properties) are logically compossible. This is the only objection the atheist can make (at least in the modal form–arguing against S5 probably isn’t the best move either…).


3 Comments to “The Reverse Ontological Argument”

  1. See J.N. Findlay’s article, “Can God’s Existence be Disproved.” retrieved here: http://www.ditext.com/findlay/god.html

    Very interesting argument, but I believe Prof. Findlay eventually did not hold to his first argument.

  2. I’ve written a little about the reverse ontological argument when addressing Steven Law’s Evil God Hypothesis. As I mentioned in The Evil God Challenge – Flipping Arguments, as well as Why the Evil God Challenge Fails, this flip also fails because good and evil are not equal and opposite – good is greater than evil, because
    1. evil can be seen as a privation of good – not a substance in itself, but the ABSENCE of good.
    2. as a non-entity, evil can not create and is not created, so it is by definition lesser than good
    3. by definition, we see can and do define good as qualitatively positive, while evil as negative (we also do so qualitatively, I would argue).

    The answer is thus – evil is not created, it is the removal of good through the willfulness of the created creatures that brings evil into existence.

    So it does not make sense to say that positive objective morals can be created by an evil God, because evil is just a lack, not a positive created thing

  3. Max,

    The problem can’t be with premise 2, because premise 2 is a tautology. It’s true by definition.

    Your answer appears to beg the question in favor of the ontological argument. You seem to think that the first premise in Plantinga’s version must be true since there is no incoherence in the notion of a MGB.

    But by the same reasoning, there is no incoherence in a world without a MGB either, so by that reasoning there must be a possible world in which a MGB does not exist. And if so, then a MGB doesn’t exist in any possible world, including the actual one.

    One of these two premises is true:

    1. There is a possible world in which a MGB exists.

    1′. There is a possible world in which a MGB does not exist.

    But it is impossible to tell which of these two premises is true. If one is true, then the other is false, and any argument that attempts to show that one is false by beginning with the truth of the other is question-begging argument. If I say that 1 is true since it is coherent, and arrive at the conclusion that 1′ is false, then I’m begging the question. If I say that 1′ is true since it is coherent, and arrive at the conclusion that 1 is false, then I’m begging the question.

    The ontological argument may be sound; we just can’t know it. At least, not from modal reasoning alone.

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