The Ontological Argument

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Anselm's First Formulation

Proslogion (Discourse on the Existence of God)

God= the greatest being that can be concieved of.

"the fool says in his heart, 'there is no God'."

Anselm was the philosopher to propose the original ontological argument and would go on to defend it from his contempories like Gaunilo of Marmourtiers.

What exists in reality is better than that which exists only as a thought.

A God that actually exists is better than a God that only exists in your mind.

God must exist or else He wouldn't be the greatest being you can think of.

For example, a perfect girlfriend who exists in reality is a lot better than one you imagined.

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Gaunilo's Criticism

On Behalf of the Fool

Gaunilo used the reductio ad absurdum to argue against Anselm.

He argued that we can picture a perfect island. The greatest possible Island that you can concieve of.

Just because we can think of this island, doesn't mean it actually exists.

"The fool might make this reply: This being is said to be in my understanding already only because I understand what is said."

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Anselm's Second Formulation

Anselm's second formulation of the ontological argument was made in responce to Gaunilo's criticism.

1) the greatest possible being is either: a necessary being or a contingent being.

2) a necessary being is greater than a contingent being.

3) the greatest possible being must be a necessary being.

4) If the greatest possible being can be concieved, it must be a necessary being and so it is impossible to conceieve that it does not exist.

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Descartes' Ontological Argument

Meditations of First Philosophy.

Had to use the argument,it was a priori. Everything but a priori and thought can be doubted.

First Formulation

1) I have an idea of a supremely perfect being.

2) Necessary existence is a perfection.

3) Therefore, a supremely perfect being exists

Second Formulation

1) Whatever I clearly and distinctly perceive to be contained in the idea of something is true of that thing.

2) I clearly and distinctly perceive that necessary existence is containted in the idea of God.

3) Therefore, God exists.

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Kant's Critism

Immanuel Kant said that existence cannot be a normal predicate, as Descartes claims. 

God exists is in the form of "S is p." 'S' means substance while 'P' means property.

"S is p" statements are true if and only if there is something called S that exists and has P.

"God exists" is true if and only if there is something that exists called God and that it has existence.

"God does not exist" is true if and only if there is something that exists called God and that it does not exist."

Norman Malcom said that while contingent existence is not a real predicate, necessary existence is. The statement "God doesn't necessarily exist" makes sense because it is true if and only if there is something called God that exists but does not exist necessarily.

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Alvin Plantinga's Modal Ontological Argument

The Nature of Necessity

God= a maximally great being (MGB). God possesses all of the 'greater making properties' like love, wisdom and power but not the 'lesser making properties' like evil, corruption and ignorance.

1) It is possible that an MGB exists

2) If it is possible that an MGB exists then it must exist in some possible world.

3) If an MGB exists in some possible world, then it must exist in every possible world.

4) If an MGB exists in every possible world, then it exists in the actual world.

5) If an MGB exists in the actual world, then an MGB exists.

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The Ontological Argument, Faith and Reason

Most people believe in God as a matter of faith rather than actual logic.


For fideists, the argument has little significance. Some say using logic to try and argue for God damages religious believe. Soren Kierkegaard argued that belief in God requires a leap of faith and using logic removes the passionate involvement with God.


The ontological argument is prima facie (very simple) and so seems easily to dismiss. Many just ignore it. If you don't understand the ideas of necessary and contingent existence, it appears easy to refute.

Betrand Russell: the ontological argument is like magic, it makes you thihnk the impossible has occured.

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Does the Argument Prove God's Existence?

Proslogion was primarily a prayer to God. It was Anselm's attempt to understand that which he already believed. "I do not seek to understand that I may believe, but I believe in order to understand." Anselm himself did not see the argument as a substitute for faith.

The argument is appropriate for the belief in a transcendent God. It doesn't use a posteriori but a priori knowledge. Arguably, this is better for the belief in a transcendent God as there would be no empircal evidence of a transcendent God.

Aquinas' rejected Anselm's argument because he believed it is impossible to understand God. This difficultly with defining God makes it hard to support the argument. Can we ever actually define God? Some have argued that you don't have to fully understand God (or any concept) to have an idea of it. Hilbert said we can conceive of infinity without fully grasping the concept as i't's too complicated for us to understand.

The ontological argument doesn't use empirical evidence which can seem counter intuitive. Empirical evidence is more likely to pursuade us as it can be directly observed. Rationalists say that empircal knowledge is the only true knowledge.

The argument doesn't actually prove God's existence, but that was never its intention.

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Is Existence a Predicate?

Immanuel Kant: existence isn't a normal predicate. When we describe something, it is already assumed that the thing exists. To add existence as a predicate is then redundant.

Norman Malcom: necessary existence is a predicate, but contingent existence isn't.

Alvin Planting: the predicate criticism is only applicable to Descartes' argument. Anselm never claimed that existence was a property than you can add or take away. 

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Descartes' Clear and Distinct Perception

"Some of the things I clearly and distinctly perceive are obvious to everyone, while others are discovered only by those who look more closely and investigate more carefully."

For some, God's existence and definition is more obvious while others are confused and so must work harder to realise a clear and distinct perception.

Like in maths, some understand God as easily as we see that a triangle has three sides. For other's God's existence is like Pythagorean Theorem and so need to study the triangle more closely. Either way, eventually, everyone understands God and knows that His existence cannot be disputed.

"St. Thomas asks whether existence is self-evident as far as we are concerned, that is, whether it is obvious to everyone; and he answers, correctly, that it is not."

The idea of God is a clear and distinct perception, meaning that once we think of it,it can be completely understood and is undeniable.

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Analytic and Synthetic Statements

Analytic statements are when the predicate is part of the definition of the subject. Analytic statements are known a priori as you can use simple logic to work out whether they are true or not.

The triangle has three sides

Synthetic statements are when the predicate simply describes the subject. Synthetic statements are known a posteriori as you need to empircially observe the subject to work out whether the statement is true or not.

The triangle is an equilateral.

The ontological argument assumes that existence is part of God's definition and that the statement "God exists" is analytic.

In Dialogues Concerning Natural Religion, David Hume said that nothing can be proved to exist a priori. The statement "God exists" is synthetic, not analytic. 

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Aquinas' Criticism

Summa Theologica

A priori arguments for the existence of God are not convinving. You can only prove God through a posterirori arguments after experience of the world.

"To know that God exists in a general and indefinite way is implanted in us by nature."

God is completely trancedant and it is impossible for the human mind to ever understand Him.

Only God can understand God.

"For the human mind does not have an intuition of the essence of God."

You therefore can't use God's nature to argue for His existence.

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Criticisms of Plantinga

Some say the idea of a MGB is incoherent and so can't exist in any possible world. Some also argue that 'greatest' is not an objective standard. The only reason wisdom is better than ignorance is because we think it is.

Some say that as soon as you agree some properties are objective and mind independent, then an MGB would possess them. If you don't accept that some properties are completely objective then you are left with nihilism and subjectivism.

As long as existence is an objective property, then an MGB is greater for having it rather than not having it.

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