The closeness with which a book is to be indexed depends partly upon
the nature of its contents and partly upon the ideas of the author
or publisher. Some indexes contain only the page references; some
are so analytical that a reader can gain an excellent idea of the
subject-matter itself. These, however, represent the two extremes. The
ordinary index aims to give every reference necessary to enable the
reader to locate easily the subject-matter for which he searches, but
not a synopsis of that subject-matter. The entries should cover, then,
with more or less minuteness, as desired, the following:
(_a_) Proper names, whether of persons, places, religious or political
bodies, etc.
(_b_) Events and periods.
(_c_) Titles of books to which reference is made.
(_d_) Specific topics or subjects.
(_e_) Definitions.
(_f_) Vital statements.