Anselm’s Ontological Argument

From Saint Anselm of Canterbury’s Proslogion, chapter II. Though Anselm’s formulation may initially seem a bit confusing, in some ways it gives a better illustration how the ontological argument is supposed to work.

  1. God is a being than which nothing greater can be thought; or God is maximally great.

    “We believe you to be something than which nothing greater can be conceived.”

  2. The fool understands (1), so the fool conceives a maximally great being.

  3. The fool conceives this maximally great being as existing only “in the understanding”. That is, the fool thinks the maximally great being is merely a figment of her imagination, and does not actually exist.

    “But, surely, when the fool hears the words ’something than which nothing greater can be conceived,’ he understands what he hears, and what he understands exists in his understanding, even if he doesn’t think that it exists.”

  4. A maximally great being who actually exists is greater than a similar being who exists only in the mind.

    “If it were to exist just in the understanding, we could conceive it to exist in reality too, in which case it would be greater.”

  5. When the fools conceives something (call it X) as existing only in the mind, she is cannot be conceiving a maximally great being, because by (4) it is possible to conceive something greater—an X which exists in reality, and not just in the mind.

    “Therefore, if that than which a greater cannot be conceived exists just in the understanding, the very thing than which a greater cannot be conceived is something than which a greater can be conceived.”

    “Hence, if that than which a greater can’t be conceived can be conceived not to exist, then that than which a greater can’t be conceived is not that than which a greater can’t be conceived. But this would be a contradiction.”

  6. Hence (2) and (3) are contradictory.

  7. But it is clear the fool understands (1), so (2) cannot be false.

  8. So the odd one out is (3), so the fool must admit that such a maximally great being must exist in reality, and not just in the mind.

    “Without a doubt, then, something than which a greater can’t be conceived does exist—both in the understanding and in reality.”

    “Therefore, he who understands God to be that than which a greater can’t be conceived cannot conceive of His not existing.”