كتاب الحيوان (Book of Animals)

...from the fire within it. Air is quick to transmute into fire and quick to return to its original nature. It is not that when it is absent, it has cut off to a higher form of its own and connected, returning to its origins. Because its parts also approach in the air, for they were latent in the firewood, interpenetrating and contracted within it; when they appeared, they expanded and spread out. The flame is merely what transmuted into fire, because air has a close relationship with fire. Water is a barrier between them, for fire is dry and hot, and water is moist and cold, while air is hot and moist. It resembles water in terms of moisture and clarity, and resembles fire in terms of heat and lightness. Thus, it differs from them and agrees with them. Therefore, it is permissible for it to flip toward them with a quick flipping, just as air is squeezed when it transmutes into moisture and acquires density, until its parts return as rain. Water is the opposite of fire, and air is a difference to them, not an opposite. It is not permissible for an essence to flip to its opposite until it flips primarily to its difference. It may be correct for water to flip to air, then air to flip to fire; and air to flip to water, then water to flip to earth. There must be a flipping in order and graduation. Every essence has premises, for water may transmute clay into rock, and likewise in reverse, rock may transmute into air, and air into rock, only according to this progression, and not without order.

(Abu Ishaq said) to those among the skilled proponents of accidents who said this: You have claimed that the fire we observe did not come out of the firewood, but that the air surrounding them heated up and transmuted into fire. Perhaps the firewood from which much water flows—that water was not in the firewood, but that place of air transmuted into water? And that place of air is no more entitled to transmute into water than the way of smoke in transmutation is the way of fire and water. If people measure that, and claim that the fire we observe, and that water and smoke, in the density of smoke and its blackness—and what accumulates from it at the bottoms of pots and the ceilings of kitchens—is merely air that transmuted, then perhaps ash is also air that transmuted into ash? If you say the ash, in its first heavy accumulation at the bottoms of pots and in the bellies of the ceilings of bathhouse hearths—which was managed with some management—is more entitled to have transmuted into earth, then if the proponent of accidents measures and claims that the firewood dissolved entirely, transmuting some of it into ash as some of it was fire once, and some transmuted into water as some of it was water once, and some transmuted into earth as some of it was earth once, without saying that the air surrounding it transmuted into ash, but rather that some of the mixtures of the firewood transmuted into ash...