Ontological Argument

Argument - attempts to prove God - reason alone

A priori - starts on definition of God > reality

Analytic - true by definition alone

Deductive - conclusion reached - God exists - only one possible that can be deduced from its premises 

God - existence is logically necessary

Existence - contingent - depends on God to exist 

• Prayed for single short proof - demonstrate everything about God including nature & existence
• Believed God - true by logical necessity
• Prove God - analysis of terms & meanings - avoid obstructions from natural world
• Prove God - reductio ad absurdum - aims to demonstrate truth of something by reducing to absurdity - opposite of what you are trying to prove
• For Anselm - opposite of conclusion = God does not exist - absurd

• Defined God - TTWNGCBC - no greater being could exist
• Believer & non believer intuitively know concept of God
• TTWNGCBC - possesses all perfections
• Existence = perfection
• 2 types of existence: existence in re (reality) / intellectu (mind)
• Mind & reality > mind alone - something greater could be thought of?
• Therefore - God exists in mind & reality

• Reformulated ontological proof - terms of necessary existence
• Rationalist - prove God - unaided human reason - discounting evidence from sensus
• Basing argument on reason alone = a priori
• Doubting his knowledge - proved his existence 
• "I think therefore I am"
• Created an argument for the perfect being

• He exists
• In mind - concept of PB
• Concept of PB - come from PB itself - could not conjure up concept on his own
• PB exists in order to be perfect
• Idea of God as supremely PB
• Such supremely PB must have perfection of existence
• Impossible to think of God as not existing
• Therefore God exists 

• Modern form of argument
• Imagine - number alternative worlds, including own
• Whatever world, God exists
• God exists in all possible worlds - maximially great
• If God possesses all attributes of God (3 O's) in all possible worlds - maximally excellent
• God's existence is necessary - must exist in all and have all characteristics in them due to God being maximally great & excellent

Anselm

• Logical - conclusion deduced - only possible one
• Such great being - God - perhaps beyond proof of empiracle evidence? This would mean argument correct

Descartes

• Logic - rationalist - reason alone - initially seems argument is correct

Aquinas -> Gaunilo

• 'Perfect island' claim
• Logic of argument - applied to other things than God -> leads to invalid conclusion
• Replaced God with island - to conceive of island & all its perfections - does not guarantee existence - argument incorrect

Anselm replied:

• Only applies to God not any other contingent being
• Misunderstood argument

Descartes -> Kant

• Existance - not predicate - not quality/characteristic
• 'Exists' does not add to our understanding - must establish existence of something before we can say what it is like
• By defining God into existence & claiming existence is attribute - incorrect - Gods existence must be established before definition can be made

Moore

• Backed up Kant
• Existence cannot be grammatically used as predicate
• 'Some tame tigers' does not add to understanding - 'God exists' - not make argument correct - existence not predicate

Argument does not work

Aquinas

• Acknowledges God exists as necessary being
• God cannot be proven by human intellect/reason alone
• Anselm made a transitional error - definition > reality - cannot define something into existence 

Also

• arguments cannot be based on reason alone - lack of empirical evidence of the universe