William Lane Craig on The ontological argument
Craig defends Plantinga's modal ontological argument as a sound proof that a maximally great being exists.
Craig employs Alvin Plantinga's modal version of the ontological argument: if it is possible that a maximally great being exists, then a maximally great being exists in some possible world. A maximally great being, by definition, exists in all possible worlds. Therefore, a maximally great being exists in the actual world.
The argument's force depends entirely on whether the key premise — that it is possible for a maximally great being to exist — is true. Craig argues that this premise is intuitively plausible: the concept of a maximally great being is coherent, and there is no logical contradiction in the idea. Since the burden is on the atheist to show such a being is impossible, and no such demonstration has been provided, the premise stands.
Craig acknowledges that the ontological argument is rarely convincing on its own and typically presents it as part of a cumulative case. Its value, he suggests, lies in shifting the burden of proof: once you grant that God is possible, you are logically committed to God's existence.
“If it is even possible that a maximally great being exists, then a maximally great being does exist. The atheist must maintain that it is impossible that such a being exists.”