The Ontological Argument

Sandra LaFave

Anselm’s Version

P1: God is the greatest conceivable being (the being “than which nothing greater can be conceived”).

P2: If such a being didn’t exist in reality, you could imagine a being just like it except your imaginary being does exist in reality. In other words, if the greatest conceivable being didn’t exist in reality, you could conceive of a being greater than the greatest conceivable being.

P3: But that’s a contradiction (an absurdity): It’s not logically possible to conceive of a being greater than the greatest conceivable being.

C:   Therefore, God, the greatest conceivable being, must exist in reality.


Descartes’ Version (in Meditation V)

P1: God is the greatest conceivable being.

P2: The greatest conceivable being must possess all perfections to the highest degree.

P3: Existence is a perfection. (An existing X is always better – more perfect – than an imaginary or non-existent one.)

C:   Therefore, God, the greatest conceivable being, must exist.


Critical Analysis

You might think both these arguments are circular — that they assume in advance exactly the point they are trying to prove. Why? P1 in both cases already appears to state that “God is the greatest conceivable being”. But he couldn’t be greatest conceivable being if he didn’t exist already. Yet Anselm and Descartes were both good logicians; they wouldn’t advocate an obviously circular argument.

Rather, P1 in both arguments is not an implicit claim that God already exists; rather, it is intended as a claim about the meaning or definition of the word “God”. P1 should be re-written as follows, adhering to conventions regarding use and mention:

P1: “The word ‘God’ means ‘the greatest conceivable being’.”

The subject of P1 is now a word, not a being. So circularity isn’t the real problem. The critiques that follow are more to the point.

  1. The Humean critique: see DP p. 152 ff. Anselm’s Ontological Argument attempts to give a logical derivation of the statement “God exists”. The demonstration begins with the definition of the word “God” and is based on the principle of non-contradiction. But definitions are relations of ideas (analytic, based on linguistic conventions — we make them up), while statements about existence are always matters of fact (synthetic, established by observation, not mere logical demonstration). You can’t “define something into existence.”

  2. The Kantian critique: “existence is not a predicate”. A “predicate” is an attribute or property of something; it’s something you say about a subject. The OA assumes existence is a property like other properties; but that’s not so. Rather, other properties presuppose existence; something has to exist in the first place in order to have any other property. In modern parlance, there’s a category mistake in thinking of existence as the same kind of predicate (i.e., in the same category) as regular predicates.

    “Perfections,” whatever else they may be, are at least predicates. So by modus tollens, if existence if not a predicate, it can’t be a perfection. The argument goes:

    P1: If existence is a perfection, it’s a predicate like other predicates.

    P2: Existence is not a predicate like other predicates.

    C: Therefore, existence is not a perfection.

  3. P3 in Descartes’ version seems not very clear. If Descartes means it’s always better for something to be real than not, well, that seems just false: I’d rather have the idea of nuclear war than real nuclear war, wouldn’t you? If Descartes means that something has to exist in order to be fully what it is potentially – e.g., a nuclear war couldn’t be a perfect nuclear war if it didn’t exist – well, that just seems to fortify Kant’s objection. P3 would in effect be saying that something that exists is prima facie better than something that doesn’t, simply because the existing thing is and the non-existing thing isn’t. The perfect nuclear war couldn’t be the perfect nuclear war if it had no be-ing, i.e., existence. But this ignores what Kant noticed: the imperfect nuclear war, the harmless nuclear war, the green nuclear war, whatever kind of nuclear war you want to specify couldn’t be imperfect, harmless, green, etc., unless it, too, had being. That is, being or existence is not like other properties (perfect, imperfect, harmless, green, etc.).




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