If someone says "Everything I say is a lie", are they telling the truth? Or are they lying?
It can't be true cause it contradicts itself: 'everything I tell you is a lie' and hes telling the truth.
The reason it can be a lie is - If he's lieing about saying 'everything he says is a lie', it doesn't mean that everything he says is the truth. It just means that maybe half the things he says is a lie. So if he only lies about half of things, than saying he lies about everything would be a lie.