According to the general classification, there are: humans and lower animals. A little more mysterious: humans, lower-level animals, demons and gods. Ah, wait a minute, is there something missing from the system? Ah yes. Have you ever heard of the phrase "Half Things in the Hall of Satisfaction"? Of course they are not low-level animals, but they are not one of the latter two. To put it bluntly, it would probably be "a living being placed between existence and non-existence."