Letter: This letter does not in fact describe itself

From Chris deSilva, Dianella, Western Australia

Brian Smith asks whether the word “heterological” is self-descriptive and thus autological, or heterological and non-self descriptive (Feedback, 22 April). The question was discussed by the German mathematician Kurt Grelling in 1908 and is known as the Grelling-Nelson paradox.

As Feedback notes (20 May) it is one of a class of self-referential paradoxes. Probably the oldest of these is the statement of Epimenides the Cretan that “all Cretans are liars”. A more direct example is the sentence “this sentence is false”, which is the centrepiece of Kurt Gödel's proof of the inconsistency of complete logical systems – and thus an inspiration for Alan Turing's definition of computing.

My answer to the question about the word “heterological” is simple: it is neither autological or heterological but paradoxical.