  According to various Russell/Tarski type theories, sentences are regimented to levels of a hierarchy and restricted in scope about what they can express; then liar-type sentences are, on this sort of solution, “nonsense”. Appeal to non-significance is then meant to avoid paradox. Goddard and Routley are concerned that philosophers have been too eager to condemn theses that “are neither gibberish nor ungrammatical” (4).