 Especially since Boolos  (1984),  it is widely accepted that there is an important distinction between plural quantification (‘there are some things such that…them…’) and singular quantification over sets (‘there is a set of things such that…it…’), and between applying a predicate collectively to some things (‘these people could lift a piano’) and applying a predicate to a set (‘this set of people could lift a piano’) (see the entry on  plural quantification).[5]  ‘Natural’ is sometimes used as a plural predicate (Dorr  2007;  Rosen  2015).  It would be tendentious to equate the claim that some things are collectively natural with the claim that they form a natural class: for example, the things that are not charged seem collectively rather natural, although they presumably do not form a class (since if they did, it would have to include itself as a member). It is more plausible to go the other way, analysing ‘natural class’ as ‘class whose members are collectively natural’. The task of explaining plural naturalness in terms of the naturalness of properties raises similar difficulties to that of explaining the naturalness of classes.