1. A Mickey Mouse Guide to the Ontological Argument
Only the fool hath said in his heart that there is no God!

2. What type of argument is it?
It is an a priori argument. That means, it is not based on our experiences of the world but relies on reason alone.
It is a deductive argument. That means, if the premises (supporting statements) are true, then the conclusion must be true. It gives a certain, rather than probable/improbable conclusion.
It is an analytical argument. That means, its truth or falsity is given by the definition of the terms used (e.g. ‘this triangle has three sides’ is analytically true; ‘triangle’ = ‘three sided object’).

3. Once more… a posteriori inductive synthetic
So, it’s an a priori, deductive and analytical argument. It’s not based on experience and observation, it’s not probabilistic but gives a certain conclusion, and finally, its truth depends on the meaning of the terms used.
EASY! Only the fool of Psalm 14 could fail to get a good grade on this topic.

4. Meet St Anselm of Canterbury…
Hi, I’m the philosopher St Anselm. I was Archbishop of Canterbury in the late 11th century. I first devised the ontological argument in parts 2 and 3 of my book, the Proslogion (written 1078).
Some philosophers aren’t entirely sure that Anselm was trying to prove that God exists. Perhaps instead he sought to bring an element of reason and reflection to his own personal faith. As he says in his Proslogion: “I believe in order to understand.” Perhaps proof of God follows from faith already gained…

5. Proslogion 2
Assuming that Anselm is trying to give a proof of God, his main argument is developed in Proslogion 2.
He begins by defining God as “that than which nothing greater can be conceived”. That means, it is impossible to think of anything with greater value or which has qualities (knowledge, power, etc.) to a greater degree.
According to Anselm, even “the fool” (Psalm 14) who denies God at least has a concept of God present in the mind.
Once we have a concept of God, we ask, does God exist merely in the understanding or in reality as well?
If God existed merely in the understanding, then we could conceive of a being great (one which existed). Therefore, the greatest conceivable being cannot exist in the mind only, but must exist in reality as well.

6. Greatest Conceivable Being All knowing All powerful All loving Just
Dead easy!
Greatest Conceivable Being
All knowing
All powerful
All loving
Just
Timeless
EXISTING
Not So Great a Being
All knowing
All powerful
All loving
Just
Timeless
Non-existent
It is impossible to conceive of a ‘greatest being’ which does not really exist, since then it would not be the greatest. Existence is a real property which a true concept of God must possess. Existence is a ‘great making property’. If we have a true concept of God then he MUST exist.

7. Proslogion 3
In Proslogion 3, Anselm seeks to show that God’s existence is necessary. That means, logically, he is a being that cannot not exist.
Let us assume that God is the greatest conceivable being. Would it be possible for him to go out of existence? No, because a being which could not cease to exist would be greater.
Similarly, would it be possible for God to have come into existence, having previously not existed? No, because a God who has always existed would be greater.
Therefore, Anselm shows that the greatest conceivable being (God) cannot not exist – his existence is necessary.
Everything but God exists contingently (it might not exist), but only God exists necessarily.

8. Gaunilo’s Objection: What about the greatest conceivable island?
The monk and philosopher Gaunilo rejected Anselm’s argument by making a parody of it. Let us say that we have a concept of the greatest conceivable island – beautiful and great in all respects. Now, let us ask, does this island exist in the mind only or in reality as well?
According to Gaunilo, Anselm’s logic is absurd because it demands that this island too exists: “for if it did not exist, any other land existing in reality would be more excellent than it”. The greatest conceivable island must exist…
The perfect island must exist?...

9. Responding to Gaunilo
Anselm could actually respond to Gaunilo in two different ways. His first argument is that islands can only exist contingently – their non-existence is always a possibility. So, to speak of an island which cannot not exist is nonsense. By contrast, only God exists necessarily. Only the greatest conceivable being could exist necessarily.
The second argument he could use is that an island can never possess maximal properties. No quality it could have could ever be possessed to the maximum degree. Does it have tasty fruit? It could always have a bit more. Is the scenery nice? It could always be a little bit nicer. God is fundamentally different because the properties he is supposed to possess are maximal properties.
Anselm: not beaten yet

10. That’s Anselm sorted. But is his argument convincing
That’s Anselm sorted. But is his argument convincing? Is it true that a concept of God in the understanding can lead us to God’s existence?
You need to evaluate that claim to gain AO2 marks.

11. A different ontological argument: René Descartes
The French philosopher René Descartes was a very lazy gentleman who spent most of his day in bed and the rest of his time studying philosophy. In his Discourse on Method he made the well-known argument “I think, therefore I am”. For Descartes, the existence of the self could be considered a known logical fact. Once this is accepted, we can then seek knowledge of the wider universe. According to Descartes, the second important piece of knowledge following from our own existence is knowledge of God. Perhaps we can prove that he exists too, merely by logic.

12. Angles equal to two right angles
Let’s start off with a definition of God. By ‘God’ we mean a ‘supremely perfect being’. By definition, therefore, God must exist. Why? Because existence is a perfection. A thing which did not exist would by definition not be perfect, because the existing version would be more complete. So, anything perfect by definition must exist.
“Existence can no more be separated from the essence of God than the fact that its three angles equal two right angles can be separated from the essence of a triangle.”
Triangle:
Angles equal to two right angles

13. More objections to ontological arguments: Kant
The philosopher Immanuel Kant lived in the late 18th century. He invented the phrase ‘ontological argument’ to describe the efforts of Anselm and Descartes. Kant was not at all convinced by such ‘proofs’.
His first main point is that ‘God does not exist’ is not self-contradictory. It is a statement which may be true or false. Any statement about an object can be self-contradictory, but if the object is held not to exist in the first place then it has no essence to be contradicted.
Kant’s second point is the (slightly) famous phrase “existence is not a predicate”. That means, in the statement “so and so exists” the fact that he “exists” adds no real information about him. By talking about “so and so” in the first place, we assume that he exists. Ontological arguments say that existence is one of God’s qualities, but it’s not really a quality at all.

14. But maybe Kant is wrong…
Kant’s first objection arguably deals with Descartes pretty well – there’s nothing self-contradictory about saying that God does not exist. But what about Anselm? Brian Davies is less sure. He argues that Anselm is not trying to say that we can move directly from an idea of God to knowledge of his existence. Instead, Anselm’s focus is upon the claim that the greatest conceivable being cannot exist merely in the mind. This is different from saying that God’s non-existence is self-contradictory.
The second point is also contestable. We can think of statements in which existence seem to add something meaningful about the subject. If an object can be conceived of as existing or not existing, then to say that it exists means something. If an idea exists in the intellect, then it is meaningful to consider whether it exists in reality as well. For example, saying that Father Christmas exists in my mind and in reality as well tells us something about the object, because we allow for his possible existence in the intellect alone.

15. Once more, Kant: First objection:
Stating that ‘God does not exist’ is not a contradiction. Unless we assume that an object exists in the first place, we cannot make contradictory statements about it.
Second objection:
“Existence is not a predicate”. Saying that X exists does not add real information about X, because by talking about X in the first place we assume that X does indeed exist.
Reply to first objection:
Anselm is not so much saying that a denial of God is a contradiction. Rather, he is suggesting that the greatest conceivable being cannot exist merely in the mind. There is a difference.
Reply to second objection
Existence is a meaningful predicate when applied to an object which can be conceived of as existing or not existing. Anselm’s argument is about the real existence of the God which exists in the intellect.

16. A modern argument: Norman Malcolm
1. The definition of God is that of a necessary being – he must exist. If his non-existence were possible, he would not be the greatest possible being and would not properly be God.
3. It thus follows that God’s existence is either necessary or it is impossible. There cannot be such a thing as a merely possible necessary being, for what is necessary cannot not exist.
2. So, God might or might not exist, but if he does exist then his existence is necessary.
4. God as an impossible being is self-contradictory and absurd.
Therefore, God exists.

17. One last argument: Alvin Plantinga
Alvin Plantinga seeks to modify Malcolm’s argument with what are called ‘possible world semantics’. This is the way some philosophers seek to represent logical possibilities. If something is possible, they say ‘in a possible world there exists X’. Plantinga’s use of this method gives what is called ‘the modal ontological argument’.
There is a possible world in which there exists a being of maximal greatness (it must exist) and maximal excellence (omniscience, omnipotence, etc).
Our world is a possible world. Therefore, the maximally great and maximally excellent being must exist in our world too.
Therefore, God exists
If a maximally great and maximally excellent being exists in one possible world then it must exist in all possible worlds, or else it would not be maximally great and excellent.
The only problem here is that we seem to be able to conceive of a possible world without a maximally great and maximally excellent being – that’s no contradiction as such.