102. In choosing between two names not exactly synonymous, consider whether there is difference enough to require separate entry; if not, treat them as synonymous.
Ex. Culture and Civilization, Culture and Education.
103. Of two subjects exactly opposite choose one and refer from the other.
Ex. Temperance and Intemperance, Free Trade and Protection, Authority (in religion) and Private judgment. Reasons for choice the same as between synonyms.
To this rule there may be exceptions. It may be best that works on theism and atheism should be put together, perhaps under the heading God; but Theists and Atheists as bodies of religious believers ought certainly to go under those two headings, and therefore it is appropriate to put works in defence of theistic doctrines and those in defence of atheistic doctrines under Theism and Atheism.
(h.) Subject-word and subject.
104. Enter books under the word which best expresses their subject, whether it occurs in the title or not.
It is strange that the delusion ever should have arisen that “a catalogue must of necessity confine itself to titles only of books.” If it does, it can not enter that very considerable number of books whose titles make no mention or only an obscure or a defective mention of their subjects (§ [85]), and it is at the mercy of deceptive titles (e. g., Channing’s sermon “On a future life,” which treats of Heaven only, Irving’s History of New York, Gulliver’s Travels). A man who is looking up the history of the Christian church does not care in the least whether the books on it were called by their authors church histories or ecclesiastical histories; and the cataloguer also should not care if he can avoid it. The title rules the title-catalogue; let it confine itself to that province. {51}
(i.) Homonyms.
105. Carefully separate the entries on different subjects bearing the same name, or take some other heading in place of one of the homonyms.