 Many contemporary sense-datum theorists, however, will not be moved by this challenge, since they are happy to accept the rejection of naturalism as a consequence of their theory (Robinson (1994), Foster (2000)). On the other hand, one might think that there is no conflict here with naturalism, as long as experiences themselves are part of the natural order. But if sense-data are non-ordinary in being mind-independent but non-physical, then it is much less clear how naturalism can be maintained (cf., what Martin (2004, 2006) calls “experiential naturalism” which serves as a constraint on theories of experience and rules out some but not all forms of the sense-datum theory).