Tuesday, July 12, 2022

Alvin Plantinga's Modal Version of the Ontological Argument for God's Existence


(I re-post this occasionally, because it is so interesting.  The modal version of the OA bypasses Kant's critique of Anselm's OA, which is that 'existence' is not a predicate.)

Here's one way to state Plantinga's modal version of the ontological argument. argument. (Modal logic uses the three modes of being - possible, probable, necessary.)

  1.  God, if he exists, is a necessary being. That is, if God exists at all then he exists in every possible world.
  2. It is [logically] possible that God exists.
  3. If it is possible that God exists, then there is some possible world in which God exists.
  4. If God exists in some possible world then, because he is a necessary being, he exists in all possible worlds.
  5. God, then, exists in all possible worlds.
  6. If God exists in all possible worlds, then he certainly exists in this one.
  7. God, therefore, exists.
Here's another version of this argument.

1. It is possible that a necessarily existing being exists.
2. Therefore, a necessarily existent being exists.