A single sentence says it is false. Is it true?
Consider the sentence: 'This sentence is false.' If it's true, then what it says is accurate, which means it's false. But if it's false, then what it says is inaccurate, which means it's true. Which is it?
Reveal the answer
Neither, consistently: assuming either truth value forces its opposite. Ancient versions trace to the philosopher Eubulides of Miletus in the 4th century BCE, building on an earlier puzzle attributed to the semi-legendary Cretan Epimenides ('All Cretans are liars'). The paradox later became central to Alfred Tarski's and Kurt Godel's formal work on the limits of self-referential logical systems.