the idlers, are beginning to question our established knowledge. But the majority of men, and particularly Germans, still defend _a priori_ judgments, on the ground that without these, perfect knowledge would be impossible, there could be no regulation of the course of natural phenomena, and no looking ahead. 8 To escape from the grasp of contemporary ruling ideas, one should study history. The lives of other men in other lands in other ages teach us to realise that our "eternal laws" and infallible ideas are just abortions. Take a step further, imagine mankind living elsewhere than on this earth, and all our terrestial eternalities lose their charm. 9 We know nothing of the ultimate realities of our existence, nor shall we ever know anything. Let that be agreed. But it does not follow that therefore we must accept some or other dogmatic theory as a _modus vivendi_, no, not even positivism, which has such a sceptical face on it. It only follows that man is free to change his conception of the universe as often as he changes his boots or his gloves, and that constancy of principle belongs only to one's relationships with other people, in order that they may know where and to what extent they may depend on us. Therefore, on principle man should respect order in the external world and complete chaos in the inner. And for those who find it difficult to bear such a duality, some internal order might also be provided. Only, they should not pride themselves on it, but always remember that it is a sign of their weakness, pettiness, dullness. 10 The Pythagoreans assumed that the sun is motionless and that the earth turns round. What a long time the truth had to wait for recognition! 11