I told you it was an assumption, not a proposition whose correctness I can demonstrate. It is however an assumption I believe to be true.No, we have been here before. That you act in your mind as if the world is real, doesn't mean that the world is real. You use a belief in real to say that other beliefs are not relevant because of your beliefs, which are not really beliefs.
That is what we are playing. Your belief in real is not really a belief.
And as I also pointed out, it's an assumption you share and use. If you do so not thinking it's true then perhaps you can explain why you like to act as though it were true anyway.