First, the desert is the country of madness. Second, it is the refuge of the devil, thrown out into the "wilderness of upper Egypt" to "wander in dry places." Thirst drives man mad, and the devil himself is mad with a kind of thirst for his own lost excellence--lost because he has immured himself in it and closed out everything else. So the man who wanders into the desert to be himself must take care that he does not go mad and become the servant of the one who dwells there in a sterile paradise of emptiness and rage.