 Let F :  Set → Set   be a power polynomial functor.     We know that F is  monotone (it preserves the subset relation on sets), and  it is not hard to check a slightly stronger property:  F preserves inclusion maps between classes:    An inclusion is a  map ia, b : a → b   on classes which “doesn’t do anything”: a must be a subset of b, and for all x ∈ a,  i(x) = x.   We say that F is standard if it preserves inclusions in  the sense that  Fia, b  =  iFa, Fb. Once again, every power polynomial endofunctor on  Set is standard. 