I was told not to use an indefinite singular noun as a subject in the start of a sentence, so I can say such to refer to a general phenomenon:
Cats eat mouses.
A cat eats mouses.
The cat eats mouses.
*Cat eat mouses.
Anyway, I have seen a lot of sentences with an indefinite singular noun as a subject:
French food is delicious.
and typically, they are often some more abstract things:
Philosophy is interesting.
and more exceptions. I remember there must be many exceptions with non-abstract nouns in indefinite singular, but I cannot come up now.