 The intuitive idea just mentioned has been expressed in different ways. Some say that qualia ‘have no hidden sides’. Others say that qualia are not natural kind terms in that it is not up to the sciences to tell us what having an experience of a particular kind amounts to (we know what it amounts to by having them and attending to the quality at issue). It is quite clear that an account of this intuitive idea has to be one of the ingredients of a dualist defense of the knowledge argument. Nida-Rümelin (2007) develops a technical notion of grasping properties which is intended to serve the purposes of dualists who argue against materialism using the assumption that in the special case of phenomenal concepts the relation that the thinker bears to the property he conceptualizes is more intimate than in other cases: the thinker understands what having the property essentially consists in. This idea can be used to block familiar objections to the knowledge argument in particular those falling into the Old fact/ New Knowledge category. A similar basic idea but formulated within a different theoretical framework is elaborated in Stephen White (2007). 