On That He Cannot Be Thought Not To Exist by Anselm

“The [being] exists so truly that it cannot be thought not to exist. For it is possible to think that something exists that cannot be thought not to exist, and such a being is greater than one that can be thought not to exist. Therefore, if that than which a greater cannot be thought can be thought not to exist, then that than which a greater cannot be thought is not that than which a greater cannot be thought; and this is a contradiction. So that than which a greater cannot be thought exists so truly that it cannot be thought not to exist.”

-Anselm “That He Cannot Be Thought Not To Exist”

The argument is that the existence of God, defined as that than which a greater cannot be thought, is so necessary and true that it would be contradictory to deny. The first premise is that it is possible to think of an object that cannot be thought not to exist as existing, in other words conceiving of an object that “has to exist” as existing. The second premise is that a being that cannot be thought not to exist is greater than a being that can be thought not to exist. Here, the quality of greatness is existing so necessarily that it cannot be thought of not to exist. The third premise states that if God can be thought not to exist, then something greater can be thought. This is a contradiction because by definition nothing greater than God can be thought of, leading to the reducto ad absurdum demonstrating that God cannot be thought not to exist. Due to the second premise, “cannot be thought not to exist” must be an attribute of God, a being that is perfectly great.

Objections to Anselm include Gaunilo’s famous parody, which uses a perfect island in place of God, arguing that, by Anselm’s logic, merely conceiving of an island which is more excellent than all other islands can bring such an island into existence. Where this objection falls apart is that one cannot possibly conceive of a perfect island. God is the only being that there can be a “greatest” conceivable, because any non-God object is defined by other attributes that are not perfection, therefore assigning the description “greatest” is nonsensical. For every instance of a non-God object, there is an infinite set of additional qualities that can make said object greater (until we inevitably arrive at God, violating the non-God object’s definition). In this example, at what point do we arrive a perfect island (how many trees, how big etc.)? One cannot conceive of a perfect island because there will always be an additional attribute that makes said island greater, thus substituting any non-God object into Anselm’s argument is not helpful and offers no guidance. Another approach is needed to object to Anselm.

Anselm’s argument is particularly strange in that Anselm claims that God exists because God’s existence is guaranteed by its definition. The inherent issue in this line of logic is that if the conclusion were true, then we can’t even suppose something that is necessary to prove the conclusion in the first place. If God exists, then the third premise needed to prove that God exists is problematic because supposing the conditional “if that than which a greater cannot be thought can be thought not to exist” cannot be achieved because God has to exist. If we accept that in order for an “if x, then y” premise to make sense that we must be able to accomplish the conditional “if x,” then Anselm’s argument falls apart, but it remains difficult to conclude whether this is necessarily the case.