19. The crafts recede from cities that are close to ruin.

This is because of what we have explained. The crafts can improve only when they are needed and when they are in demand with many people. When the condition of a city weakens and senility sets in as the result of a decrease of its civilization and the small number of its inhabitants, luxury in the city decreases and (its inhabitants) revert to restricting themselves to the necessities. The crafts belonging to luxury conditions and which depend on (luxury) become few. The master of (a particular craft) is no longer assured of making a living from it. Therefore, he deserts (his craft) for another, or he dies and leaves no successor. As a result, the institutions of the crafts disappear altogether. Thus, for instance, painters, goldsmiths, calligraphers, copyists, and similar artisans who cater to luxury needs disappear. The crafts continue to decrease, as long as the city continues to decrease, until they no longer exist.

God is "the Creator, the Knowing One." ⁹⁶