The sole reason for philosophy is captivity.

 The only fundamental reason why people keep pondering the world and why countless philosophical theories and doctrines have been produced is simply because they are trapped here and have nothing else to do with it. If humans were to be in another world, they would then think about that world instead and would never even be aware of the existence of this one. And this applies, in the broadest sense, to the entire universe as well. Humans think about this specific universe only because no other is within their grasp. Had they been in another universe, this one might have vanished without ever being discovered.