P1.3 ontological arg

• Anselm: God is that 'than which nothing greater can be conceived'
• Plantinga: God is a being of maximal excellence and maximal greatness
• the ontological argument is a priori, deductive and analytic
• Plantinga's ontological argument

  modal logic - necessary in possible world = necessary in all possible worlds

  logically possible for necessary God to exist in possible world --> necessary in all
• Kant's criticism of the ontological argument

  existence is not a predicate - adding existence to your idea of 100 coins does not change how you imagine it
• Aquinas' criticism of the ontological argument

  can't know God's essence thru reason alone, knowledge of God's existence must come from empirical observation of world
• Gaunilo reductio ad absurdum argument against onto: island
• Russell: critique of ontological arg

  existence is not a predicate as it could be used to can define anything into existence

  e.g. (1) donkeys exist; (2) Eeyore is a donkey; (c) Eeyore exists