Anthony Grayling writes:
The problem with Alvin Plantinga’s defense of theism is a simple but wholly vitiating one [Where the Conflict Really Lies, reviewed by Thomas Nagel in “A Philosopher Defends Religion,” NYR, September 27, 2012]. It is that it rests on the fallacy of informal logic known as petitio principii. Plantinga wishes to claim that we can know there is a deity because the deity has provided us with a cognitive modality, which Plantinga calls “a sensus divinitatis,” or sense of the divine, by which we detect its existence. So, we know there is a god because that god arranges matters so that we know there is a god. The circularity is perfect, and perfectly fallacious. I can claim with equal cogency that I know there are goblins in my garden because they provide me with a goblin-sensing faculty of mind…and so for anything else whatever that we would antecedently like to exist.
Plantinga assumes that everyone has a sensus divinitatis but in some of us it is faulty. The name of this fault is “rationality.”
Thomas Nagel replies:
Anthony Grayling’s charge of circularity would be right if Plantinga offered the sensus divinitatis as evidence for the existence of God, but he does not. He says merely that belief in God is knowledge if it is in fact caused by God in this way, much as perceptual belief in the external physical world is knowledge if it is in fact caused by the external world in the appropriate way. It would be just as circular to try to prove the existence of the external world by appealing to perception as it would be to try to prove the existence of God by appealing to the sensus divinitatis. But Plantinga holds that it is nevertheless reasonable to hold either type of belief in this basic way, without further proof. I assume he would deny that anyone has, or thinks he has, a basic, unmediated belief in goblins.
Clearly, Grayling is not at the level of Plantinga and Nagel. He is more of a New Atheist ideologue and polemicist than a genuine philosopher. This is shown by the sophomoric zeal with which he attempts to pin an elementary informal fallacy on Plantinga, one that "wholly vitiates" his defense of theism. It takes chutzpah and lack of respect for a formidable opponent to think one can blow him out of the water in this way. This is typical cyberpunk behavior. The punks hurl fallacy labels at each other: fallacy of composition! Hypostatization! Begging the question!
And then there is the polemical swipe Grayling takes at the end of his letter. Polemics has its place, but not in philosophy.
The palm goes to Nagel!
Here are my anti-Grayling posts.