ipse se nihil scire id unum sciat
                                                  Cicero, Academica I.16
A variation on Russel's paradox


        Obscure and intuition-bound notions can neither lead to absurd
        conclusions nor provide new and correct ones, and hence they
        fail to be useful in two important respects.
                                   Chomsky, _Syntactic Structures_, p. 5