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