In 1078, Saint Anselm of Canterbury presented a proof that God exists. We define God as a being than which no greater can be conceived. If God existed only in the mind, then we could conceive of a greater God, one who exists in both mind and reality. Therefore God cannot be merely imaginary — he must exist in reality.

Australian philosopher Douglas Gasking offered this response. The creation of the world is the worthiest achievement imaginable. Its merit is the product of its intrinsic quality and the ability of its creator. The greater the creator’s handicap, the more impressive the achievement. The most grievous handicap would be non-existence. An existent creator would be subordinate to one that does not exist. Therefore, if God is the greatest conceivable being, then he does not exist.

(William Grey, “Gasking’s Proof,” Analysis 60:4 [October 2000], 368-370.)