Problems for Descartes #4: The Ontological Argument (feat. Alvin Plantinga!)

Shifting away from Descartes' view of the mind, this post will critique one of Descartes' arguments for God, known as the Ontological Argument. When I was in college I briefly engaged with this argument in a couple of my philosophy classes, however, the formulation was a bit different than what I will critique here. Moreover, I want to attack this argument because, like dualism, it still has currency in philosophical circles, though in different forms. Since I believe the critique in this post applies to more contemporary formulations, I will also engage with one of these, that being the one authored by Alvin Plantinga.

Ontological arguments refer to arguments that seek to demonstrate the existence of God by through mere analysis of the concept of God. Unfortunately for Descartes, his formulation came long before Kant's famous objection to ontological arguments and it is quite uncertain how Descartes would respond to it. Nevertheless, I contend that the argument falls short in the light of the Kantian critique and some other considerations.

Descartes' ontological argument is as follows:
1. Whatever I clearly and distinctly perceive in a concept is true of that concept.
2. I clearly and distinctly perceive "necessary existence" belonging to the concept of God.
3. Therefore God exists.

One can get in to more detail concerning Descartes' use of  "clear and distinct ideas" in his epistemology, but for this post using his own analogy will suffice. Descartes compares the relationship between  God and "necessary existence" to a triangle and its properties. A triangle's properties are clear and distinct so they cannot be denied. According to Descartes, "necessary existence" belongs to the concept of God just as clearly, so similarly it cannot be denied that God is a necessary entity. Because of this trait, God indeed exists.

Before getting into the critique, Descartes' view of "necessity" should be explained. According to the Stanford encyclopedia, Descartes was not referring to modality or "possibility" when he used the word necessary. He meant that God was necessary in respect of his independence; his lack of dependence on any other entity for existence.

Given this view of necessity,  it becomes immediately apparent to me that the argument is not valid. In other words, God's existence does not follow from him being necessary. Platonic objects such as numbers and sets are necessary in the Cartesian sense, but their actual existence does not follow from this property. In my view, the only way that it can is if there is an additional fact concerning possibility. Thus, if the Cartesian argument is going to have a chance of being sound, it must add a premise concerning possibility, for example, "If a being's existence is wholly independent (necessary) AND POSSIBLE,then it must exist".

With this premise concerning possibility, the Cartesian argument becomes very similar to Alvin Plantinga's "Victorious Ontological Argument". Both conclude that God exists based on God's necessity and possibility. The Plantinga argument moves as follows:

1. It is possible that a maximally great being exists.
2. If a maximally great being is possible then a maximally great being exists in some possible world.
3. A maximally great being is a necessary being.
3. If a necessary being exists in some possible world, then it exists in all possible worlds.
4. If a necessary being exists in all possible worlds, then it exists in the actual world.
5. Therefore,  a maximally great being exists in the actual world.

It is clear that the property that does the work in this argument, just as in the Cartesian case is the property of "necessity". The significant difference between the two arguments is the nature of necessity. In the Cartesian case, as mentioned, necessity refers to independence, but in the Plantinga case it refers to modality or possibility. In the modal sense of necessity, an entity is necessary if it exists in all possible worlds if it exists at all, hence why it would exist in the actual world if granted its possibility.

But what would Kant say about all this?  Kant's famous objection to ontological arguments is that existence is not a real predicate or property, as it adds nothing to the concept of a thing. In the Blackwell Companion to Natural Theology, one contributing author challenges the notion that existence is not a property, but concedes that existence adds nothing to the concept of a thing. This concession, however, is enough for the Kantinan objection to be sound, because what the ontological argument attempts is the leap from the concept of God to his actual existence; the argument cannot make such a jump if "existence" is not found in the concept.

Does the Kantian objection undermine the two arguments? Though Plantinga doesn't use the word existence, it seems that he sneaks in existence as a predicate through the property of "necessity". This because by "necessity" he means "necessarily existent".The Cartesian argument also does this, but more explicitly. If "existence" cannot be found in a concept, does it follow that neither can  "necessary existence"?

At first blush, the modal sense of necessity seems to add something to a concept. It seems that one learns something new about an entity when it is learned that such an entity exists in all possible worlds if it exists at all. In this post, my main objection is that in order for something to be necessarily existent, "existence" would have to be part of the concept of that thing. In other words, something exists in all possible worlds if and only if "existence" is one of its essential properties. This is the case for any entity; something is true of any entity in all possible worlds if and only if it is an essential property of the entity. For example, a globe is round in all possible worlds because roundness is one of its essential properties; roundness belongs to the concept of a globe. In this case, we would say globes are necessarily round. Similarly, God would only be "necessarily existent" if and only if existence is one of his essential properties or belongs to the concept of God. However, given the Kantian objection, this cannot be the case. Thus, without "necessity" Plantinga's argument cannot get off the ground.

What about the Cartesian sense of necessity? This sense of  necessity, which again means something more like "independence", also seems to add something to a concept. However, as mentioned before, the only way to conclude God's actual existence from such a property would be to add a premise concerning possibility. Unfortunately for Descartes, I would contend that a premise such as "If a being's existence is wholly independent (necessary) and possible,then it must exist" does not carry compelling force and can be plausibly denied. If talk about possible words is employed, then it isn't difficult to conceive some possible worlds containing an independent entity and other possible worlds without that same entity.

Concerning possibility, moreover, my objection is that since existence is not part of the concept of a thing then I think it is the case that neither is possibility (which we have been using to mean potentiality of existence). Hence, one cannot conclude an entity's possibility from its mere concept. This is a controversial stance and it all depends what is meant by possibility. The Blackwell Companion to Natural Theology explores several different notions of possibility, but the one that is used in arguing for the existence of God is a kind of metaphysical possibility, rather than a narrow,logical notion. Thus, even if a concept is coherent, this will not grant possibility of this kind. Given the Kantian objection, I contend that this kind of possibility indeed cannot be found by merely analyzing the concept, since it would make a fact about its existence found in its concept. I think we come to know this kind of possibility either directly or indirectly from experience. For example, we know an "orange book" is possible even if we never saw an orange book, because we have background information concerning what can be orange and background information concerning the possible states of a book. The ontological argument, however, is not supposed to employ experience, nor does Descartes do so. Without establishing God's possibility, the  key premise of the argument, which I think is weak to begin with, cannot get of the ground.

Even though the two arguments use different senses of necessity, they both are severely undercut by the fact that existence cannot be found in the concept of an entity. These arguments sneak in existence using the shield of "necessity" or "possible". Thus, neither Plantinga's nor Descartes' formulations of the ontological argument survive the Kantian objection.