See here for content about the status as a proof and value for religious faith of arguments for the existence of God. It is also needed for some philosophy dialogues questions about the relevance of reason and philosophical argument for religious faith.
St Anselm’s Ontological argument
Anselm refers to Psalm 14:1 ‘the fool says in his heart, ‘there is no god’.” Since the fool can conceive of God as the greatest being, it would be contradictory to think God doesn’t exist since then God wouldn’t be the greatest being. To say there’s no God is simply to misunderstand what the word ‘God’ means. So, a priori reasoning about the meaning of the word ‘God’ can reach the conclusion that God exists.
P1. God is the greatest conceivable being (by definition)
P2. It is greater to exist in reality than the mind alone
P3. God exists in the mind
C1. Therefore, God exists in reality
Anselm uses the analogy of a painter who has an idea of what they will paint in their mind before creating the painting in reality. This is meant to show that there is a difference between an object being in the mind and being in reality.
An atheist who does not believe God exists in reality still has the idea of God in the understanding (their mind). Anselm argues that since God is that than which nothing greater can be conceived, it is incoherent to think that God exists in the mind alone because then we could conceive of something greater, i.e., that thing also existing in reality. Yet, what we conceived of is the greatest conceivable being and so it must exist in reality, otherwise it would not be the greatest conceivable being.
“that, than which nothing greater can be conceived, cannot exist in the understanding alone: then it can be conceived to exist in reality; which is greater. Therefore, if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and reality.” – Anselm.
To say that God does not exist in reality is to say that the greatest being is not the greatest being. It is self-contradictory.
Gaunilo’s ‘lost island’ response to Anselm
Gaunilo attacks the inference from God existing in the mind to the God existing in reality; the inference from P3 to C1. Gaunilo argues:
“I have in my understanding all manner of unreal objects”
“he who says that this being exists, because otherwise the being which is greater than all will not be greater than all, does not attend strictly enough to what he is saying. For I do not yet say, no, I even deny or doubt that this being is greater than any real object.”
“I should not admit that this being is in my understanding and concept even in the way in which many objects whose real existence is uncertain and doubtful, are in my understanding and concept. For it should be proved first that this being itself really exists somewhere; and then, from the fact that it is greater than all, we shall not hesitate to infer that it also subsists in itself.”
Anselm’s argument could succeed in showing that if God exists, then God is the greatest being and even that it subsists in itself, i.e., has necessary existence. However, this is not enough to show that God does exist necessarily.
Gaunilo then illustrates this with the case of a perfect lost island, which is an illustration of a thing whose real existence is ‘uncertain and doubtful’ yet is in his understanding as a concept.
Applying the logic of Anselm’s argument to this island has an absurd result (reductio ad absurdum). It is greater for this island to exist in reality, so it must exist. This would work not just for an island. The greatest or supremely perfect member of every category must exist. This is sometimes called the ‘overload’ objection because it suggests that reality would be overloaded with greatest/perfect things.
Anselm’s 2nd version of the ontological argument
In response to Gaunilo, Anselm strengthened his argument into a 2nd form.
Something is greater if it doesn’t depend on anything for its existence. An Island by definition is land enclosed by water, so part of the concept of an Island involves a dependence on things such as an ocean or a planet to exist. So, the greatest possible Island will still be contingent, which means that it is not the case that it must exist. The existence of a contingent being cannot be proven through the a priori reasoning of the ontological argument. This is because the existence of a contingent being is not a matter of definition.
There is nothing in the concept of the greatest being that involves dependence however, unlike the Island. So, Anselm can now argue that this is why the argument works for God but not an Island.
Anselm seems to have failed to respond to Gaunilo’s central contention, even if the relevance of the perfect island has been successfully refuted.
“I have in my understanding all manner of unreal objects” – Gaunilo
Even if Anselm is right that we cannot conceive of God’s non-existence, that does not prove that God does exist. It only proves that we are unable to conceive of God’s non-existence. Gaunilo objects that this is not enough:
“in the first place it should be in some way proved that a nature which is higher, that is, greater and better, than all other natures, exists” – Gaunilo
This idea of the greatest conceivable and thus inconceivably non-existent being could be one of those unreal objects that is just in our mind.
Kant develops this objection, illustrating with the example of a triangle. We can accept that it is necessary that the concept of a triangle has three sides. This shows that if a triangle exists, it must have three sides. Similarly, we could accept that ‘existing with necessity’ is part of the concept of God. Yet again, this only shows that if God exists, then God exists necessarily. It doesn’t show that God does exist necessarily.
Gaunilo & Aquinas’ objection: God is beyond our understanding
Gaunilo raises an objection to P3; the premise that the greatest conceivable being exists in the mind/understanding, as an idea. Gaunilo draws on traditional Christian theology and claims God is beyond our understanding and therefore cannot be said to be ‘in’ the understanding.
We cannot therefore go on to reason about whether it would be greater also in reality. The ontological argument therefore fails because it relies on our ability to understand and reason about things that are beyond our ability to understand or reason about.
Aquinas also made this argument against Anselm – that God’s nature, such as the ‘eternal law’ is beyond our understanding.
Gaunilo even doubts that we can understand this idea of the greatest conceivable being:
“of God, or a being greater than all others, I could not conceive at all”
“So much for the assertion that this supreme nature already is in my understanding.”
However, a full understanding of the greatest conceivable being or of God’s nature is not required for the ontological argument to work.
Anselm would not accept that we either understand God fully or not at all. Our limited understanding of God’s nature is enough to justify attributing the name ‘that than which nothing greater can be conceived’ to God.
God is a being which has traits such as power, knowledge and love yet to their greatest possible degree, i.e., omnipotence, omniscience and omnibenevolence. We can at least understand that omnipotence involves being able to do any logically possible thing, and omniscience involves knowing every true proposition. Since it is impossible to conceive of anything with greater power or knowledge than that, we can understand that God is the greatest conceivable being. We can then follow Anselm’s reasoning that, since it is greater to exist, the greatest conceivable being, i.e., God, must exist.
Peter van Inwagen illustrates and explains this point:
“even if we cannot look directly at the sun, it does not follow that we cannot see daylight. And, in Anselm’s view, our partial grasp of God’s nature is sufficient to show us that the applicability of the name ‘something a greater than which cannot be conceived’ to God is a consequence of that nature’. – Inwagen
Kant: existence is not a real predicate
Kant argued that existence was not a real predicate, meaning not a description of a thing. To say something exists is not to describe that thing, it is to describe whether it exists. Saying something exists does not describe a quality of feature that defines that thing, only that the thing exists.
Anselm’s argument depends on existence being a predicate – being part of the definition of God. His argument is that God must exist because if God didn’t exist, he wouldn’t be the greatest possible being, but God is the greatest possible being, so he must exist. Since Anselm is saying that God would not be God without existing, then Anselm is saying that existence is part of what defines God. To say God exists is therefore to describe what God is, i.e., to think existence is a predicate.
For Anselm, existence is an attribute of the concept of God, along with omnipotent, omniscient, etc. The question of whether God exists is a question of what God is. Kant argued that existence was not a predicate/attribute/quality of a thing. For Kant, what something is, is different from whether it exists.
A simple illustration: I could say ‘the cat is black’ which would describe the subject cat with the predicate ‘black’. The blackness of the cat is a description of what it is. However, if I were to say ‘the cat exists’, it doesn’t seem that the word ‘exists’ really does actually describe something about what it means to be the cat in itself. Instead, it describes that the cat exists. So, existence is not a predicate, not a description of a subject.
Kant’s illustration for this was 100 thalers (coins). Imagine you have 100 thalers in your mind as a mere concept. Then imagine you also have 100 thalers in existence, not only in the mind. You have two cases of 100 thalers, one which exists in reality and the other which only exists in your mind.
If Anselm was correct that existence is part of the definition of the concept of a thing, then the thalers which exist should be conceptually different to the thalers that do not.
However, Kant argues that the concept of what it means to be 100 thalers is no different whether it is a mere concept in your mind or whether that concept actually exists in reality as an existing thing. 100 thalers is just 100 thalers; it has the attributes of shininess and roundness, whether in your mind or in reality.
If there is no conceptual difference between the thalers in the mind and the thalers which exist in reality, then existence cannot be an attribute of a concept. Existence cannot be a defining part of the concept of a thing; it is not a predicate.
Malcolm criticised Kant, arguing that Kant’s argument only worked for contingent existence but not necessary existence, so Anselm’s second version of the argument was right. Something is contingent if it is dependent on something else for its existence. The reason for its existence is external to it. However, a necessary being doesn’t depend on anything else and so contains the reason for its existence within itself. This reason is the logical impossibility of non-existence. Since that is contained within itself in a way that contingent existence is not, Necessary existence can therefore be a part of a thing in a way that contingent existence can’t.