The question, 'Is one thing in the same genus as another or in a different one?' is also a generic question; for a question of that kind as well falls under the same branch of inquiry as the genus; for having argued that animal is the genus of man, and likewise also of ox, we shall have argued that they are in the same genus; whereas if we show that it is the genus of the one but not of the other, we shall have argued that these things are not in the same genus.