because there is only one world (and no doubt all of our conceptions fall short of the whole).
in full: "You are a little bit extreme here, James. Also kind of solipsistic or maybe imperialistic: why would you think that your world is the only world or that I would think that your world is the only world? In fact I think "your world" -- your conception of the world -- is misguided here and on other points as well."