Supposing, however, that it is disputed whether the given genus belongs at all, it is not enough to prove that one of the higher genera is predicated of the species in what it is: eg if any one has given locomotion as the genus of walking, it is not enough to prove that walking is motion in order to prove that it is locomotion, seeing that there are other forms of motion as well; but one must prove in addition that walking does not partake of any of the species of motion produced by the same division as locomotion.