Why can the status of names such as the Roman Catholic Church be uncertain?

The status of names such as "the Roman Catholic Church" is considered uncertain because they occupy a borderline position between proper names and common nouns (appellatives).1

While names are typically used for individual reference and common nouns refer to classes of entities, expressions like "the Roman Catholic Church" or "the Ministry of Education" exhibit characteristics of both categories. This ambiguity is reflected in the inconsistent use of capital letters across different languages, which serves as a primary indicator of this linguistic uncertainty. This overlap has a long historical precedent, stemming from the early tradition of using the same term—such as the Greek onoma—to describe both common nouns and names, only later distinguishing them as "general nouns" and "proper nouns" (onoma kyrion).1