The paradox of a man who states "I am lying." If he is lying, then he is telling the truth, and vice versa. Another version of this paradox is the Epimenides paradox. Such paradoxes are often analyzed by creating so-called "metalanguages" to separate statements into different levels on which truth and falsity can be assessed independently. For example, Bertrand Russell noted that, "The man who says, 'I am telling a lie of order n' is telling a lie, but a lie of order n + 1".

epimenides paradox | Eubulides paradox