A Clarifying Passage from Feser on Property Dualism

Edward Feser, Philosophy of Mind, a Beginner’s Guide (One World, 2006) p. 113.
Property dualism would thus appear to lead to absurdity as long as it concedes to materialism the reducibility of the propositional attitudes. If it instead takes the attitudes to be, like qualia, irreducible to physical states of the brain, this absurdity can be avoided: for in that case, your beliefs and judgments are as non-physical as your qualia are, and there is thus no barrier (at the least of the usual mental-to-physical epiphenomenalist sort) to your qualia being the causes of your beliefs about them. But should it take this route, there seems to be much less motivation for adopting property dualism rather than full-blown Cartesian substance dualism: it was precisely the concession of the materiality of propositional attitudes that seemed to allow the property dualist to make headway on the interaction problem, an advantage the is lost if the concession is revoked; and while taking at least beliefs, desires, and the like to be purely material undermines the plausibility of the existence of a distinct, non-physical mental substance, such plausibility would seem to be restored if all mental properties, beliefs and desires, as much as qualia, are non-physical. Moreover, property dualism raises a puzzle of its own, namely that of explaining exactly how non-physical properties an inhere in a physical substance.