What does McGinn think we cannot know?

Exactly what is McGinn saying when he claims that we cannot solve the mind-body problem? Just what is cognitively closed to us? The text suggests at least four possibilities. I work through each them in some detail, and I come to two principal conclusions. First, by McGinn's own understanding of the mind-body problem, he needs to show that we are cognitively closed to how brains generate consciousness, but he argues for something else, that we are cognitively closed to the brain property in virtue of which the brain is the basis of consciousness. Second, it turns out that McGinn is not entitled to any of the four closure possibilities