 But if the world is fundamentally ideal—if, as Mill seems to claim, our world is the world as conditioned by our mediating senses, because we can know and represent it in no other way—we might wonder why a basic harmony between the architecture of mind and world should not be taken as given, and a priori knowledge not be possible. Indeed, Mill’s claim that cognition must be mediated by some method of cognising—that any creature must perceive in this way—itself seems suspiciously unrevisable and a priori.