 He takes Einstein to defend this as a principle of individuation of physical systems, without which physical thought “in the sense familiar to us” would not be possible. Howard himself contemplates the possible failure of this principle for  entangled quantum systems,  with the consequence that these could no longer be taken to be wholly composed of what are typically regarded as their subsystems. Dickson (1998), on the other hand, argues that such holism is not “a tenable scientific doctrine, much less an explanatory one” (p. 156).