I don't see how it's promoted as fact. He presented it as "Popper’s principle". I see it more as a general rule of thumb. Have to in this case is confined to

I don't see how it's promoted as fact. He presented it as "Popper’s principle". I see it more as a general rule of thumb. Have to in this case is confined to context of the principle itself, it indicates that you have to do such and such in order to follow the principle.