 Concerning the issue whether self-reference can be avoided in deriving paradoxes, and hence whether there are genuine contradictions arising from ungroundedness, a positive answer has been given by the semantical paradox of Yablo 1993: there are infinitely many agents , etc., each one claiming the same sentence: “at least one agent following me is lying”; but this yields a contradiction – see also the entries on  self-reference  and  liar paradox.  The issue this construction raises, namely whether circularity and self-reference are necessary and sufficient conditions to the appearance of paradoxes, has been further considered in Yablo 2006 (see Cook 2014 for a comprehensive study on this matter, and Halbach and Zhang 2017 for a proof without diagonal lemma). Moreover, the connection between the incompleteness phenomena and paradoxes has been extended up to include Yablo’s paradox, as a special case of Liar-type paradoxes (Kurahashi 2014, Kikuchi and Kurahashi 2016).