Anselm, Descartes and objections
1. God is the greatest conceivable being.
2. God exists in the understanding.
3. To exist in reality is better than merely to exist in understanding.
4. Thus, if God exists merely in the understanding, then we can conceive of something greater than God, namely a being just like God, but who also exists.
5. But it is impossible to conceive of a being that is greater than the greatest conceivable being.
6. Thus it is impossible that God exists merely in the understanding.
7. Thus God exists in reality as well as in the understanding.
8. Thus God exists.
Rea and Murray find Anselm’s original formulation of this argument, as it appeared in his famous work the Proslogion, to be problematic. What exactly are we to make of the second premise? They refer to Descartes’ version of the argument for help, and take notice of his slightly different notion of God as a being containing all perfections rather than Anselm’s greatest conceivable being. They reconstruct the argument as follows:
1. God is the greatest possible being (GPB).
2. The GPB possesses every perfection that would make a being great.
3. Existence is a perfection that would make a being great.
4. God possesses existence […thus God exists]
Gaunilo of Mamoutier penned a famous objection to Anselm’s argument, entitled “In Defense of a Fool,” where he facetiously replaces “God” with “Lost Island” as a proof for the existence of the greatest conceivable island; his objection aims to show how Anselm’s argument leads to absurd conclusions. But does the argument really work when we plug in other greatest conceivable things? That depend on what makes something the greatest of its kind. How many miles of beach would the greatest conceivable island have (100, 1,000, 10,000)? Certain types of perfection (such as the greatest number of miles of beaches) don’t have an intrinsic maximal value, and thus Mamoutier’s objection hasn’t identified a valid candidate for use in Anselm’s argument . Not so fast though, this objection might cut both ways if some of God’s own great-making properties don’t have an intrinsic maximal value (e.g., God ‘s being perfectly loving).
But is existence a property at all, much less (or should I say much more) a great-making property? Kant answered in the negative, maintaining that existence is always presupposed for a thing which is propertied (more simply, Kant maintains that “my cat is black” presupposes “my cat exists”). [1] Murray and Rea don’t see why a precondition (for ascribing other properties) can’t itself be a property. For example: taking up space is a precondition for having the property of being red, but taking up space is itself a property. Their response seems reasonable, except that existence is the precondition for all other properties (or so Kant argues). But this fact alone doesn’t show that existence isn’t itself a property (or at least I can’t see how it does).
The third and most popular, potent objection to this argument is simply that is begs the question; it assumes God exists before in the premises. After we modify the first premise to avoid this objection, it’s hard to see how we can reach any satisfactory conclusion. For instance, if the first premise reads “For anything to count as God, that thing would have to possess existence” we can follow the argument through and see how this is undesirable. Rea and Murray, and many other philosopher, think the traditional argument fails to avoid this third objection.
The Modal Ontological Argument
A new rendition of this argument has surfaced via recent work in an area of philosophy known as modal logic. Modal logic deals with possibility and necessity. Rea and Murray define a possible world as “a comprehensive description of the way the universe might be … the maximally comprehensive description of our universe is the actual world.” Contingent beings only exists in some possible worlds but not others. A necessary being, if it exists, would exist in all possible worlds. A being possesses a property necessarily if it has that property in all (relevant) possible worlds (Plantinga refers to the properties that a person has necessarily as their “essence” ). For example, Arnold Schwarzenegger is 6 feet tall ascribes a property to Arnold, but Arnold could be 5 feet tall in another possible world. On the other hand, Arnold Schwarzenegger is a person ascribes a property to Arnold that he holds in all (relevantly) possible worlds. Having laid the ground for understanding modal logic, the modal ontological argument is presented as follows.
5.20 God is the greatest possible being.
5.21 The greatest possible being is one that possesses all perfections necessarily.
5.22 Necessary existence is a perfection.
5.23 It is possible that the greatest possible being exists.
5.24 If it is possible that the greatest possible being exists, then that being exists necessarily.
5.25 God exists necessarily.
5.26 God exists.
My rough attempt at stating it with a little less precision and a little less jargon:
If we can show that the great possible being exists is true in at least one possible world, then we have shown that God exists. Why? Since the greatest possible being would possess all perfections necessarily (see premise 5.21), this means it would have those perfections in every possible world where it exists. Since necessary existence (that is, existence in all possible worlds) is a perfection, then it follows that the greatest possible beings exists in all possible worlds is true in all possible worlds if true in any possible world. Since the actual world (the one we live in) is one of those possible worlds, it follows that God exists in the actual world.
Premise 5.23 is susceptible to refutation. For instance, some philosophical theologians think that the concept of a greatest possible being entails a contradiction, thus disqualifying God from existing in any possible world. In other words, if a perfect being is shown to be conceptually incoherent, this argument fails. A more modest critic might simply insist that we withhold judgement on this argument until we have resolved all the apparent contradictions in philosophical theology. But a rebuttal can be given to both critics here. Since premise 5.23 asserts the possibility that the greatest possible being exists, then the ontological defender’s response to conceptual incoherence should be to adjust the concept of the greatest possible being to get in line with what is possible. Does omnipotence and impeccability entail a contradiction? No problem, just tweak the concept to remove the contradiction.
One final objection to be raised is that necessary existence is impossible (premise 5.22). Rea and Murray don’t think that any convincing arguments have been offered in this direction. [2]
1 Alvin Plantinga, in God, Freedom and Evil (1977), proceeds meticulously through the details of Kant’s objections in a section entitled, “The Irrelevance of Kant’s Objection.” Pdf is available here. Chris Heathwood wrote a reply entitled, “The Relevance of Kant’s Objection.”
2 See Edward Feser’s summary of Plantinga’s ontological argument here. Also, see William F. Vallicella’s articles on broadly logical necessity (he disagrees with many philosophers who say that conceivabality entails possibility) as well as A Modal Ontological Argument and an Argument from Evil Compared.
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