What history teaches us is that man does not change arbitrarily; he does not transform himself at will on hearing the voices of inspired prophets. The reason is that all change, in colliding with the inherited institutions of the past, is inevitably hard and laborious; consequently it only takes place in response to the demands of necessity. For change to be brought about it is not enough that it should be seen as desirable; it must be the product of changes within the whole network of diverse casual relationships which then determine the situation of man.