We don’t even have to worry about John wanting to tell the truth in the future.
Class,
We don’t even have to worry about John wanting to tell the truth in the future. The fact
that you won’t believe him when he tells his first lie is enough (and I would hope that all of us would not believe John, if everyone lies all the time). We’ve reached the contradiction. Think about it. What is the point of telling a lie?
Can you see the contradiction? If not, just focus on the question I just asked, What is the point of telling a lie?