 Avempace wrote a book of a genre similar to that which physicians write to preserve and acquire health, the so called tadbir as-sihha. He referred to Galen and what Galen wrote in the Preservation of Health as a model for his Rule of the Solitary. To preserve physical health requires knowledge of the natural science about delivering justice, for example, and knowledge of political science. Avempace concluded that since his treatise aims at acquiring and preserving spiritual health, “it reverts to the natural and political science” (IB-RS-AP: 12.15–16; IB-RS-berman: 129; IB-coll-genequand: 128 §38). What binds natural and political science? Forms, insofar as men have similar and different forms, and forms are related to nature.