The basic neural processes going on in conscious thought have to be just the same as the basic neural processes going on when the brain nonconsciously thinks. These processes are the only things neurons and sets of neurons do. Consciousness is just another physical process. So, it has as much trouble producing aboutness as any other physical process. (The Atheist’s Guide to Reality, pp. 192-193)
Of course, this does boil down to a belief that people don’t have beliefs. But what is interesting here is not Rosenberg’s personal eccentricities. Rather, it is the fact that he’s simply following the logic of what is claimed by a great many people.
It is not uncommon for people, in defense of materialism, to insist that tangible evidence is the only factor to be considered in the discussion. To use the now infamous sound byte “that which is presented without evidence can be dismissed without evidence”. I don’t accept this approach myself, but it is not insignificant that those who do should reject the idea that thoughts are about things. Certainly, no one has been able to present physical evidence for the “aboutness” of thoughts.
Of course, I’d say that there is evidence that thoughts are about things–quite a bit, actually. But this would require taking a broader definition of evidence than the typical materialist would allow.
And that would, of course, open the door for all kinds of evidence that runs counter to materialism. This doesn’t show it to be false outright, but it would immediately cost its proponents their central argument (that there is “no evidence” for theism).
So materialists find themselves in a precarious place, wanting to insist that evidence is always physical on the one hand, but not wanting to deny thought on the other. Rosenberg’s sentiments aside, it seems obviously true that there is far more reason to believe in thought than to believe that all evidence is physical.
It is also important to remember that this argument holds even for those who take thought to be a physical process in the brain. For, we are not discussing whether or not the mind is physical (though it is not), but whether there is physical evidence for the idea that we think about things.
And there is not. No amount of physical data about the brain gives us evidence that thoughts are about things. For that, we’ll simply have to take the test subject’s word for it (or, better still, our own experience of thinking).
But, if we’re willing to accept inner experience and/or testimony as evidence, materialism has a number of very difficult challenges facing it. And, personally, I don’t think it can hope to answer these challenges.