Physics

...and he heals and becomes a non-physician in his capacity as a physician. Since we say, most strictly, that the physician does something, undergoes something, or comes to be from a physician if he does or undergoes or comes to be these things as a physician, it is clear that coming to be from "what is not" also means this, [coming to be] as "not being." Because the ancients did not make this distinction, they abandoned the search and, through this ignorance, went so far astray as to believe that nothing else comes to be or exists, essentially abolishing all generation. But we ourselves also say that nothing comes to be simply from "what is not," yet we do say that it comes to be from "what is not," for instance, coincidentally. For something comes to be from privation, which is in itself "what is not," which does not exist in the thing. This is viewed with wonder, and it seems impossible that something should come to be from "what is not." Likewise, nothing comes to be from "what is," nor does "what is" come to be, except coincidentally. But this comes to be in the same way; for instance, if an animal comes to be from an animal, or a specific animal from a specific animal, such as if a dog were to come from a dog, or a horse from a horse. For the dog would come to be not only from an animal, but from an animal, yet not in its capacity as an animal; for this is already present. But if something is going to become an animal not coincidentally, it will not be from an animal, and if something is [to become] an existing thing, it will not be from what is, nor from what is not; for it has been said by us what "from what is not" means, namely, as "not being." Furthermore, we do not abolish that everything is or is not. One way [to solve the puzzle] is this; another is that it is possible to speak of the same things in terms of potentiality and actuality; this has been defined with greater precision in other works. Thus, the puzzles which forced people to abolish some of the things mentioned are solved; for it is because of this that earlier thinkers went so far off the path of generation, corruption, and change in general. For if they had seen this nature, it would have dissolved all their ignorance.