Anselm's ontological argument

• Anselm's argument is an a priori argument, which means the argument relies on logic, not observation or sense experience
• Anselm's argument is also deductive, which means the argument aims to give certain proof. If the premises are true, then the conclusion must be true
• The Ontological argument is based on the claim that God's existence can be deducted from his definition – that once God is correctly defined, there can be no doubt that he exists
• The proposition 'God exists' is a priori/deductive - it can be known to be true without reference to sense experience, just by thinking about God's name
• 1. In the proposition 'God exists' the subject 'God' contains the predicate 'exists' so therefore God must exist​
• God's existence is a necessary truth, not a contingent one
• 'God is that, than which nothing greater can be conceived'
• 'God is that, than which nothing greater can be conceived'​

  A) Greatest

  B) Exist

  
• P1 – God is a being than which nothing greater can be conceived 
• P2 – This is a definition which even a fool understands in his mind, even though he does not understand it to exist in reality.  ​
• P3 – There is a difference between having an idea in the mind and knowing that this idea exists in reality
• 1. P4 – For example, a painter has an idea in his mind of what he wants to paint; but when he has painted it, that idea now exists both in his mind and in reality​
• P5 – It is greater to exist both in the mind and in reality than to exist only in the mind
• P6 – If God existed only in the mind, I could think of something greater, namely a God who existed in reality also
• 1. Conclusion – Therefore in order to be the greatest conceivable being, God must exist both in reality and in the mind. ​
• We can therefore reduce Anslem's arguments to two essential premises and a conclusion. ​

  1. God is the greatest conceivable being ​
  2. It is greater to exist in reality than to exist only in the mind ​
  3. Therefore, as the greatest conceivable being, God must exist in reality​
• Criticisms of the ontological argument from Gaunilo


  Gaunilo uses an island in his argument. He came up with the ontological argument for a lost island. Gaunilo uses the logic of Anselm that it is better to exist in reality than in the mind. It is possible to conceive of the most perfect and real lost island. It is greater to exist in reality than it is to exist in the mind. Therefore, the most perfect and real lost island must exist in reality ​
• Anselm's reply to Gaunilo ​

  Anselm argues that necessary existence is a predicate only of God, and not things. You cannot compare God, the greatest conceivable  being to an island. To be perfect, an island would have to be 'that island than which no greater can be conceived'
• Anselm's reply to Gaunilo

  Anselm also argued that different people have different ideas of a perfect island, as it's down to opinion. You might never meet another person who's island is the same as yours. Most people think of God as the greatest conceivable being ​
• Anselm's reply to Gaunilo


  In summary, Anselm gives a clear response to Gaunilo's 'perfect lost island' argument. He shows that necessary existence is a predicate only of God and not objects
• Strengths of Anselm's Ontological argument

  It is a deductive argument. This means if it succeeds, it is a proof of the existence of God. It does not depend on observation
• Strengths of Anselm's Ontological argument

  The argument can be interpreted in different ways. For example, Karl Barth believed that Anselm never intended for his argument to be an argument for the existence of God. Instead, Barth believed that Anselm had a religious experience
• Kant's criticisms of the ontological argument

  Existence is not a predicate. Kant's objection is simple: existence is not a real predicate, because it adds nothing to the concept of a thing. A real predicate gives us new knowledge of a subject.
• Kant's criticisms of the ontological argument 


  1/2 - We can accept the proposition that 'existing necessarily' is part of what we mean by 'God', but it does not follow from this that God exists in reality. Anselm's ontological argument in effect claims that the proposition 'God exists necessarily' is analytic (true by definition).
• Kant's criticisms of the Ontological argument 


  2/2 - Think, for example, the statement 'A bachelor is an unmarried man' is obviously analytic and true by definition, because that's how we define a bachelor. ​Now take the following proposition 'Bachelors exist'. How do we know that bachelors exist? We do by experiencing them. If in your family you have an unmarried man of marital age, then clearly 'Bachelors exists' is true because you've seen one.
• Weaknesses of Anselm's Ontological argument


  Several scholars reject it, largely because of the 2 major objections of Kant
• Weaknesses of Anselm's Ontological argument ​

  The starting point of Anselm's argument is that God is defined as 'that than which nothing greater can be conceived'
• Weaknesses of Anselm's Ontological argument ​


  Some would argue, however, that any attempt to define God would be limiting God. Anything that can be classified and analysed can be understood by humans. Thomas Aquinas insisted that we do not know God's definition, so Anslem must be wrong. ​