Rosenberg's Argument Against Beliefs

[Whateverist]

1: If naturalism is true, then beliefs are brain states.
2: Brain states are physical configurations of matter.
3: Therefore, if naturalism is true, beliefs are physical configurations of matter.
4: In order to qualify as beliefs proper, they need to have the property of intentionality (i.e. to refer to or be "about" something)
5: Physical configurations of matter cannot, in virtue just of its physical structure, composition, location, or causal relation, be “about” another configuration of matter in the way original intentionality requires.
6: Therefore, if naturalism is true, beliefs cannot be "about" anything.

Notice how incomplete step one is as written. Brains states which underpin beliefs aside from being configurations of matter are already about something. Similarly if I write out a "Spare any change?" sign on a scrap of paper, the piece of paper is just a piece of inert material, compositionally. But now it also conveys my belief that someone is going to throw me some coin, which is my intention. If a scrap of paper can convey my intention, then it would seem that, whatever material my brain may be composed of, can not prevent it from doing the same.

[Excellent example of the presumption of the rational mind. On what basis do you prefer to dismiss this argument?]