There are three main courses open:
(1) We can consider the subject to be the phrase as it reads, as Agricultural chemistry, Survival of the fittest, which is the only possible method in (a) and undoubtedly the best method in (c), (e), and (f), and in most cases of proper names, as Democratic Party, White Mountains, Missouri River (but see § [26]).
(2) We can make our entry in (b), (c), and (d) under what we consider the most significant word of the phrase, inverting the order of the words if necessary; as, Probabilities (instead of Theory of probabilities); Earth, Figure of the; Species, Origin of the, the word Origin here being by itself of no account; Alimentary canal, Canal being by itself of no account; Political economy, Political being here the main word and economy by itself having a meaning entirely different from that which it has in this connection.
(3) We can take the phrase as it reads in (c), (d), (e), and (f), but make a special rule for a noun preceded by an adjective (b), first, that all such phrases shall when possible be reduced to their equivalent nouns, as Moral philosophy to Ethics or to Morals, Intellectual; or Mental philosophy to Intellect; or Mind, Natural philosophy to Physics, Sanitary science; or Hygiene, Scientific men to Scientists; or Social science to Sociology; and, secondly, that in all cases where such reduction is impossible the words shall be inverted and the noun taken as the heading, as Chemistry, Agricultural; Chemistry, Organic; Anatomy, Comparative; History, Ancient; History, Ecclesiastical; History, Modern; History, Natural; History, Sacred. [40] {52}
The objection to (1) is that it may be pushed to an absurd extent in the case (b). A man might plausibly assert that Ancient Egypt is a distinct subject from Modern Egypt, having a recognized name of its own, as much so as Ancient history, and might therefore demand that the one should be put under A (Ancient) and the other under M (Modern) [41] and similar claims might be made in the case of all subject-names to which an adjective is ever prefixed, which would result in filling the catalogue with a host of unexpected and therefore useless headings. Nevertheless the rule seems to me the best if due discrimination be used in choosing subject-names.
[40] This rule is proposed by Mr. Schwartz and carried out, with some exceptions, in his catalogue of the New York Apprentices’ Library.
[41] Which would be much like putting Williams’s “Shakespeare’s Youth” under Youthful Shakespeare. Individuals should not be divided.
The objection to (2) is that there would often be disagreement as to what is “the most important word of the phrase,” so that the rule would be no guide to the reader. But in connection with (1) and as a guard against its excesses (2) has its value. The combined rule might read:
107. Enter a compound subject-name by its first word, inverting the phrase only when some other word is decidedly more significant or is often used alone with the same meaning as the whole name.
Ex. Special providences and Providence, Proper names and Names.