Rosenberg makes no secret of the fact that this is the motivation for his attacks on introspection. He sees clearly that any trust that our basic experience of our inner lives, even so much as belief that our thoughts and consciousness really exist, will show belief in materialism to be false.
I’ve discussed the reasons for this elsewhere, but the thing to note here is that there is no good reason to doubt our introspection. If all that we know about anything is based on experience, then it would take a powerful argument indeed to contradict something so basic as the idea that we actually have thoughts.
Rosenberg thinks he has this, of course, in pointing out that we are sometimes wrong about our inner lives. This, of course, is no more reason to conclude that thought doesn’t exist than the fact that our senses are sometimes wrong is a reason to conclude that the physical universe doesn’t exist.
But the only alternative, accepting that we do indeed have thoughts about things, leads us inevitably to the conclusion that thought is something more than physical processes in the brain. And this would mean the rejection of a materialist view.
And, for all I disagree with Rosenberg, he’s right about this. If our own thought life is even remotely reliable in telling us what a mind is like, then materialism is false.