Central Problems of Philosophy

Prof. Stephen Schiffer

Fall `98


Handout 6


  1. God =df an all-good, all-knowing, all-powerful, immaterial being who exists necessarily and is the creator of all things other than itself.
  2. x exists contingently iff x exists but might not have existed; i.e., x exists in the actual world, but thereís some possible world in which x doesnít exist.
  3. x exists necessarily iff itís metaphysically impossible for x not to exist; i.e., x exists in every possible world.

  4. St. Anselmís version of the Ontological Argument:
    1. My concept of God is the concept of the greatest possible thingói.e., of a thing greater than which cannot exist.
    2. If that concept didnít include existence, it wouldnít be that of the greatest possible thing, for a thing that exist is always greater than a thing that doesnít exist.
    3. Itís therefore inconceivable that God doesnít exist.
    4. Therefore, God exists.
  5. Our version of the Ontological Argument:
  6. Itís metaphysically possible that God exists.

    Therefore, God exists.

  7. An ontological argument for the existence of unicorns:
  8. Itís metaphysically possible that there are unicorns.

    Therefore, there are unicorns.

  9. A principle of modal logic: If itís possible that itís necessary that S, then itís necessary that S.
  10. Our version of the Cosmological (First Cause) Argument:
    1. Everything that comes into existence must have a cause.
    2. There cannot be an infinite series of causes of things that come into existence.
    3. Therefore, there must be a first cause that did not come into existence but has always existed.
    4. Therefore, God exists.
  11. The Argument from Design (the Teleological Argument):
    1. Things that exhibit structural and functional complexity (such as the eye) must have been created by an intelligent designer: the greater the complexity, the more intelligent the designer.
    2. The universe contains things exhibiting a very high degree of structural and functional complexity.
    3. Therefore, the universe must have been created by an extremely intelligent designer.
    4. Therefore, God exists.
  12. Inference to the Best Explanation:
  13. The best explanation of the origin and nature of the universe is that God exists and created this universe.

    So, it is highly probable that God exists (at the least we ought to accept the hypothesis that God exists).

  14. Leibnizís "proof" that this is the best of all possible worlds:
    1. God exists.
    2. If God exists, it is all good, all powerful, and all knowing.
    3. If God is all good, then it created what it believed was the best world it was able to create.
    4. If God is all powerful and all knowing, then the possible world it believed was the best it was able to create was the best of all possible worlds.
    5. Therefore, the actual world is the best of all possible worlds.
  15. The anti-Leibniz proof that God doesnít exist:
    1. The actual world isnít the best of all possible worlds.
    2. Same.
    3. Same.
    4. Same.
    5. Therefore, God doesnít exist.