1 God is (by definition) a being than which no greater being can be thought. (premise)
Arguably God is (by definition) a being greater than which can be thought. Otherwise God is defined by man rather than man by God.
2 Greatness includes greatness of virtue. (premise)
3 Therefore, God is a being than which no being could be more virtuous. (from 1, 2)
I would agree with 3
4 But virtue involves overcoming pains and dangers. (premise)
5 Indeed, a being can only be properly said to be virtuous if it can suffer pain or be destroyed. (premise)
Greatness according to the definition in premise 2 MUST include greatness of virtue if premise 2 is to be true. Premise 3 is true ONLY if premise 2 is true. Virtue as defined in premise 4 invloves overcoming pains and dangers. Therefore greatness as defined by these premises MUST include the possibility of pain and suffering if 3 is to be true, leading to the conclusion in 5.
6 A God that can suffer pain or is destructible is not one than which no greater being can be thought. (premise)
7 For you can think of a greater being, that is, one that is nonsuffering and indestructible. (premise)
Here is where the argument self destructs. If greatness according to it's own premises is measured by among other things pain and suffering then 6 and 7 cannot be true. If however 6 and 7 are true, then 2 and therfore 3 cannot be true. The argument suffers from self contradiction over its own definition of greatness.
In essence, 2, 3, 4 and 5 contradict 6 and 7. They are not compatable according to their own definition of greatness. Which leads me back to premise 1 which I expressed concern over initially.
Being that Jesus in the bible suffered on the cross I would suggest He displayed virtue. Therefore fulfilling the greatness qualification in that category.
Therefore due to the contradictory statements within the argument, 8 cannot be concluded from this argument.
Nice try.
Yet more proof, along with the Argument form Evil and the Argument from Non Belief, that god, as biblically described and believed in, is logically impossible.
No, it is naive to suggest this.