  A difficulty in making sense of this is that the idea of a physical fact is not definitively specifiable. To tie the idea too closely to current physics would rule out fundamental changes in that subject; to leave it floating free might seem to allow anything at all to qualify. But clearly Quine does not mean just any subject that someone might call by the name “Physics”. He has in mind a subject continuous with our physics, alike or superior in its coherence and in its explanatory power. (In particular, it would not have “an irreducibly psychological annex”: 1986a, 403f.). If phenomena occurred which could not be explained by any theory of that kind, then Quine’s physicalism would go by the board. 