and a tree from a date stone, and fruit from a tree. Their variation through motion and rest, coming together and separating—as when water or soil is dispersed and gathered—does not entail any difference in the essential nature of the body. Beyond this comes variation in its colours and tastes: being red, green, yellow, sweet, or sour involves variation beyond mere motion, such as the motion of celestial bodies and winds.

Next, variation through growth and nourishment—as when young animals and plants grow larger—is another kind of variation, involving changes, increases, and other features absent from mere changes in colour and motion.

Then water becoming vapour, and firewood becoming smoke or ashes, constitute yet another kind, involving a transformation and alteration of their essential nature that does not occur in the preceding cases.

Then the bringing forth of fruits from trees, a human being from semen, and crops from plants is something different from all of these. The tree does not diminish when fruit emerges from it, nor is its essential nature transformed. Likewise, the earth does not diminish when crops emerge from it, nor is its essential nature transformed.

The same applies to a human being emerging from his mother and an egg emerging from a hen. The creation of a chick from an egg, however, is of the same kind as the creation of a human being from semen.