(18) Whence both these divisions are to be rejected, and only the division of the genus into species is approved, by which both the identity that is in the genus is characterized, and the diversity which subsists in the specific differences.

(20) It is best, then, to divide the genus into two, if not into three species.

(25) Accordingly, in the larger definitions the number of the species that are discovered are in the ten Categories; and in the least, the principal points of the nearest species being taken, mark the essence and nature of the thing. But the least consists of three, the genus and two essentially necessary species.

(9) Accordingly we must first take the genus, in which are the points that are nearest those above; and after this the next difference. And the succession of differences, when cut and divided, completes the "What it is." There is no necessity for expressing all the differences of each thing, but those which form the species.

Some Hindoos were exhibiting an elephant in a dark room, and many people collected to see it. But as the place was too dark to permit them to see the elephant, they all felt it with their hands, to gain an idea of what it was like. One felt its trunk, and declared that the beast resembled a water-pipe; another felt its ear, and said it must be a large fan; another its leg, and thought it must be a pillar; another felt its back, and declared the beast must be like a great throne. According to the part which each felt, he gave a different description of the animal. One, as it were, called it "Dal" and another "Alif."

(19) The species is always contemplated in a part. On the other hand, however, if a thing is part of another, it will not be also a species. For the hand is a part of a man, but it is not a species. And the genus exists in the species. For [the genus] is both in man and the ox. But the whole is not in the parts. For the man is not in his feet. Wherefore also the species is more important than the part; and whatever things are predicated of the genus will be all predicated of the species.