It's confusingly simple.
" This statement is false."
If this statement is false, then it's true. But if it's true, then it's a lie and therefore false. Since its false, it's true. But if it's true, then it's a lie and therefore false. Since its false, it's true. But if it's true, then it's a lie and therefore false. Since its false, it's true.
And yes, I did just copy that three times.
