Full Idea
It seems to be one of the central points of constructing systems of ontological categories that everything can be placed in some category or other.
Gist of Idea
The aim is that everything should belong in some ontological category or other
Source
Jan Westerhoff (Ontological Categories [2005], §49)
Book Reference
Westerhoff,Jan: 'Ontological Categories' [OUP 2005], p.122
A Reaction
After initial resistance to this, I suppose I have to give in. The phoenix (a unique mythological bird) is called a 'phoenix', though it might just be called 'John' (cf. God). If there were another phoenix, we would know how to categorise it.