Kitap 7
8
But further we must also divide by the differentia of the differentia. E.g., having feet is a differentia of animal; then in turn we must discover the differentia of animal having feet qua having feet. Accordingly we should not say that of that which has feet one kind is winged and another wingless, (that is if we are to speak correctly; if we say this it will be through incapability), but only that one kind is cloven-footed and another not; because these are differentiae of foot, since cloven-footedness is a kind of footedness.
9
And thus we tend always to progress until we come to the species which contain no differentiae. At this point there will be just as many species of foot as there are differentiae, and the kinds of animals having feet will be equal in number to the differentiae. Then, if this is so, obviously the ultimate differentia will be the substance and definition of the thing, since we need not state the same things more than once in definitions, because this is superfluous.
10
However, it does happen; for when we say footed two-footed animal we have simply said animal having feet, having two feet. And if we divide this by its proper division, we shall be stating the same thing several times, as many times as there are differentiae.
11
If, then, we keep on taking a differentia of a differentia, one of them, the last, will be the form and the substance. But if we proceed with reference to accidental qualities—e.g. if we divide that which has feet into white and black—there will be as many differentiae as there are divisions. It is therefore obvious that the definition is the formula derived from the differentiae, and strictly speaking from the last of them.
12
This will be clear if we change the order of such definitions, e.g. that of man, saying two-footed footed animal; for footed is superfluous when we have already said two-footed. But there is no question of order in the substance; for how are we to think of one part as posterior and the other prior?
