Wikipedia:Gooch paradox

In philosophy and wiki-logic, Gooch paradox or inactive paradox (Gouchas lógos--Γουχας λόγος—in Ancient Greek) is the statement "I am no longer active", posted to page on Wikipedia, most commonly on a user page or user talk page. Trying to assign to statement a classical binary truth value leads to contradiction (see paradox).

If "I am no longer active" true, then the editor can't be posting statement that she is not active. Common sense, but it requires some degree of competence to realise.