Ontological arguments

What is a deductive argument?

• Valid (the argument is structured so that is the premises are true then the conclusion must be true)

• Sound (the premises are true and the argument is valid)

• Proof (a deductive argument which is sound)

P1 All humans are mortal

P2 Socrates is human

P3 Therefore, Socrates is mortal

What is an inductive argument?

• Induction (an argument built by moving from a number of limited cases to all cases, or from the past to the future)

• Strong/cogent (an inductive argument with true premises leading to a conclusion that is very probably true based on the weight of the evidence based in the premises

P1 Every raven I have ever seen is black

P2 There are ten raven in the Tower of London

P3 Therefore, all these ravens are black

What is an anbductive argument?

• Inference to the best explanation (abduction examines an effect and attempts to infer from this the most likely cause / explanation)

• Affirming the consequent (this is a logical fallacy, which all abductive arguments commit)

P1 The pavements outside are wet

P2 When it rains the pavement gets wet

P3 Therefore, it has been raining recently

What is Anselm’s ontological argument?

P1 God is the greatest possible being

P2 Even a fool can understand that God is the greatest possible being

P3 The fool says that there is no God in reality

P4 The fool is convinced that God, the greatest possible being, exists only in his understanding and not in reality

P5 It is greater to exist both in the understanding and in reality, than merely in the understanding

P6 The greatest possible being, if it is genuinely the greatest, must exist both in the understanding and in reality

C Therefore, God exists both in reality and in the understanding. Moreover, the fool really is a fool, as he is denying the existence of the greatest possible being, that is a being which must exist if it genuinely is the greatest

What is Gaunilo’s Island argument?

P1 We can imagine an island which is the most excellent island

P2 It is greater to exist in reality then merely in the understanding

P3 Therefore, the most excellent island must exist in reality

• That we can imagine such a ‘perfect island’ does not, Gaunilo posits, prove that it exists - perfection does not infer existence

• Gaunilo aims to shows in this counter-example that you can prove anything exists according to Anselm’s logic, and this alone gives reason to doubt Anselm’s ontoLogical argument

What is Descartes’ ontological argument?

P1. I have the idea of God

P2. God is a supremely perfect being

P3. Existence is a perfection

C. Therefore, God exists

• Whilst Anselm hinges his argument for God’s existence on the definition of God as the greatest conceivable being, Descartes’ argument depends on the definition of God as the supremely perfect being and existence as a predicate

• Descartes claims that the statement ‘God does not exist’ is a logical contradiction in the same way that the statement ‘triangles have four sides’ is a logical contradiction

What is Hume’s objection to the ontological argument?

Hume makes the claim that there are different kinds of meaningful propositions:

• Matters of fact: Synthetic proposition that are not necessarily true by definition. These can be tested via sense data, and are thus knowable a posteriori.

• Relations of ideas: Analytic propositions that are necessarily true by definition, and thus knowable a priori

• Hume posits that the proposition ‘God exists’ is not a matter of fact, as this statement is not referring to a being that physically exists in the world

• ‘God exists’ must therefore be a relation of ideas, which fails to tell us anything meaningful about God (beyond that God exists). Such statements are therefore at worst meaningless, and at best trivial.

• Hume challenged the view that proof of existence can be established simply a priori. There must, he argues, be an empirical enquiry.

What is Kant’s objection to the ontological argument?

• Existence is not a predicate

  • Kant claims that Descartes is mistaken in treating existence as a predicate (a genuine descriptive property)

  • Kant offers the example of the difference between a hundred real gold coins and a hundred imaginary gold coins. Kant argues that existence does not Act as a descriptive property, as there is no difference between our concept of ‘100 gold coins’ and ‘100 gold coins that exist’

  • If we were to add the property ‘shiny’ or ‘heavy’, our concept of 100 gold coins would change, as these are genuine descriptive properties

  • Therefore, existence is not a predicate of God

• Being true by definition is not equivocal to existence in reality

  • Even if we were to accept existence as a predicate of God, Kant argues that this would still not guarantee God’s existence in reality

  • Imagine a unicorn. The proposition ‘a unicorn has a horn’ is true by definition, but this does not infer that there are unicorns in existence in reality

  • We might be able to accept the proposition ‘God necessarily exists’ as true by definition, but in the same way as the example above, it does not logically guarantee that God exists in reality

What is Malcom’s Ontological Argument?

P1. God cannot come into existence

P2. So if God does not exist then his existence is logically impossible

P3. If God does exist then his existence is logically necessary

P4. Either God’s existence is logically impossible or it is logically necessary

P5. God’s existence is not logically impossible

P6. Therefore God’s existence is necessary

C. Therefore God’s existence is necessary