He hopes that his work will help in the dark days that he foresees:        
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    When the world experiences a complete overturn it seems to change          
its nature in order to permit new creation and a new organization.           
Hence there is need today of an historian who can describe the state         
of the world, of its countries and peoples, and indicate the changes         
in customs and beliefs. `063059                                              
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  He devotes some proud pages to pointing out the errors of some             
historians. They lost themselves, he feels, in the mere chronicling of             
events, and rarely rose to the elucidation of causes and effects. They       
accepted fable almost as readily as fact, gave exaggerated statistics,       
and explained too many things by supernatural agency. As for                 
himself, he proposes to rely entirely on natural factors in explaining       
events. He will judge the statements of historians by the present                       
experience of mankind, and will reject any alleged occurrence that           
would now be accounted impossible. Experience must judge                     
tradition. `063060 His own method, in the  Muqaddama,  is first to           
deal with the philosophy of history; then with professions,                  
occupations, and crafts; then with the history of science and art.           
In succeeding volumes he gives the political history of the various          
nations, taking them one by one, deliberately sacrificing the unity of       
time to that of place. The true subject of history, says                     
Ibn-Khaldun, is civilization: how it arises, how it is maintained, how       
it develops letters, sciences, and arts, and why it decays. `063061          
Empires, like individuals, have a life and trajectory which are              
their own. They grow, they mature, they decline. `063062 What are            
the causes of this sequence?                                                 
  The basic conditions of the sequence are geographical. Climate             
exercises a general but basic influence. The cold north eventually           
produces, even in peoples of southern origin, a white skin, light            
hair, blue eyes, and a serious disposition; the tropics produce in           
time a dark skin, black hair, "dilatation of the animal spirits,"            
lightness of mind, gaiety, quick transports of pleasure, leading to          
song and dance. `063063 Food affects character: a heavy diet of meats,             
condiments, and grains begets heaviness of body and mind, and quick          
succumbing to famine or infection; a light diet, such as desert