All the sciences came to exist in Arabic. The systematic works on them were written in Arabic writing. - Ibn Khaldun

On account of their savage nature, the Bedouins are people who plunder and cause damage. They plunder whatever they are able to lay their hands on without having to fight or to expose themselves to danger. They then retreat to their pastures in the desert. They do not attack or fight except in self-defence. Every stronghold or (locality) that seems difficult to attack, they by-pass in favour of some less difficult (enterprise). Tribes that are protected by inaccessible mountains are safe from their mischief and destructiveness. The Bedouins would not cross hills or undergo hardship and danger in order to get to them. Flat territory, on the other hand, falls victim to their looting and prey to their appetite whenever they (have the opportunity of) gaining power over it. Then they raid, plunder, and attack that territory repeatedly, because it is easily (accessible) to them. Eventually, its inhabitants succumb utterly to the Bedouins and then are pushed around by them in accordance with changes of control and shifts in leadership. Eventually, their civilization is wiped out. God has power over His creatures.

It should be known that at the beginning of a dynasty, taxation yields a large revenue from small assessments. At the end of the dynasty, taxation yields a small revenue from large assessments.

When civilization [population] increases, the available labor again increases. In turn, luxury again increases in correspondence with the increasing profit, and the customs and needs of luxury increase. Crafts are created to obtain luxury products. The value realized from them increases, and, as a result, profits are again multiplied in the town. Production there is thriving even more than before. And so it goes with the second and third increase. All the additional labor serves luxury and wealth, in contrast to the original labor that served the necessity of life.