Note 9 — RULES FOR A DICTIONARY CATALOGUE.

Not merely the concrete classes, Natural history, Geography, Herpetology, History, Ichthyology, Mineralogy, but the abstract ones, Mathematics, Philosophy, are plainly subjects. The fact that some books treat of the subject Philosophy and others of philosophical subjects, and that others treat in a philosophical manner subjects not usually considered philosophical, introduces confusion into the matter, and single examples may be brought up in which it seems as if the classification expressed the form (Crestadoro’s “nature”) or something which a friend calls the “essence” of the book and not its subject, so that we ought to speak of an “essence catalogue” which might require some special treatment; but the distinction can not be maintained. It might be said, for example, that “Geology a proof of revelation” would have for its subject-matter Geology but for its class Theology—which is true, not because class and subject are incompatible but because this book has two subjects, the first Geology, the second one of the evidences of revealed religion, wherefore, as the Evidences are a subdivision of Theology, the book belongs under that as a subject-class.