Kitap 7
5
For there is nothing else in the definition but the primary genus and the differentiae; the other genera consist of the primary genus together with the differentiae which are taken with it. E.g., the primary genus is animal; the next below it, two-footed animal; and again, two-footed wingless animal; and similarly also if the expression contains more terms still.
6
In general it does not matter whether it contains many or few terms, nor, therefore, whether it contains few or two. Of the two one is differentia and the other genus; e.g., in two-footed animal animal is genus, and the other term differentia.
7
If, then, the genus absolutely does not exist apart from the species which it includes, or if it exists, but only as matter (for speech is genus and matter, and the differentiae make the species, i.e. the letters, out of it), obviously the definition is the formula composed of the differentiae.
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.
