Quote Originally Posted by heads all empty
1. God is the entity than which no greater entity can be conceived.

2. The concept of God exists in human understanding.

3. God does not exist in reality (assumed in order to refute).

4. The concept of God existing in reality exists in human understanding.

5. If an entity exists in reality and in human understanding, this entity is greater than it would have been if it existed only in human understanding (a statement of existence as a perfection).

6. from 1, 2, 3, 4, and 5 An entity can be conceived which is greater than God, the entity than which no greater entity can be conceived (logical self-contradiction).

7. Assumption 3 is wrong, therefore God exists in reality (assuming 1, 2, 4, and 5 are accepted as true).

There you have it
pretty good but:
1. a perfect being can not be conceived. a perfect being is omnipotent, but omnipotence is logically impossible (does an omnipotent being have the power to become more powerful? either way, they aren't omnipotent). we can't concieve how a being would complete an insurmountable task, therefore we can't conceive such a being.
2. why must perfection exist in reality? a perfect square in thought wouldn't become more perfect if such an object could be created in reality.