"I am now speaking falsely", referring to the words I just said. If I speak truly when I said this, then i am lying. If I am speaking falsely when I said this, I am speaking the truth.

So what i say is true if, and only if, it is false; which seems absurd.

One response claims that I say nothing true and nothing false. But a variant makes trouble:; Jill says "I am now not speaking truly". If Jill is not speaking truly when this is what she says she is up to, she is speaking truly. If she is speaking truly, then she must be doing what she says, that is, not speaking truly. So, it seems, what she says is true if, and only if, it is not true.

LIAR PARADOX