It appears then to follow that non-count nouns can be neither singular nor plural a point which would seem indeed to be as fundamental as any, and from which two subsidiary points follow directly. |
To us they seem like non-count nouns for naming types of stuff. |
But of course, to enforce it you have to be able to distinguish count from non-count nouns. |
Now, vanity is a non-count noun, only very rarely used in the plural. |