for each one to have whatever is possible for the other; whatever is necessary for one is necessary for the other, and whatever is impossible for one is impossible for the other. The same applies to bodies composed of substances. Thus, when they establish a judgment concerning one body, they say: “This holds for all bodies,” on the basis that they are of the same nature. Most rational people reject this, and their most accomplished thinkers have refuted the arguments advanced to establish this sameness of nature, as al-Rāzī, al-Āmidī and others have mentioned. This has been discussed at length elsewhere. In al-Ibānah (The Elucidation), al-Asharī included the assertion that bodies are of the same nature among the doctrines of the Mutazilah that he rejected.

These thinkers say that Allah singles out one of two bodies of the same nature for certain accidents, to the exclusion of the other, by His will alone, according to the principle of the Jahmiyyah, or for some other reason, as the Qadariyyah maintain. They also say that transformation from one genus into another is impossible: a body cannot become an accident, nor can one genus of accidents become another. Thus, if they were to say that bodies are created and that a created thing changes from one genus into another, this would entail transformation between genera.

They therefore say that what develops in the womb, the fruit produced on trees, and the fire produced by fire-strikers are substances that already existed in the material from which these things were created. Those substances remain, but their attributes have been changed through aggregation, separation, motion and rest.