A knowledge of each species can be acquired easily upon the basis of this general characterization: 'We shall divide each of the three kingdoms into several families which will group together all those beings that are strikingly related, and we shall review all the general and particular characters of the beings contained within those families'; in this way we shall be assured of relating all these beings to their natural families; and thus, beginning with the ferret and the wolf, the dog and the bear, we shall come to know sufficient about the lion, the tiger, and the hyena, which are animals of the same family.