“The order of the classes may, therefore, be briefly described as expressing:
- 1. Matter.
- 2. Life.
- 3. Mind.
- 4. Record.”[8]
[8] From Subject Classification, by James Duff Brown, 1906, pp. 11-13; second edition, 1914.
The only serious objection which has been urged against this scheme is the inclusion of Education, Logic, Mathematics, and the Graphic and Plastic Arts in Generalia. This course is, however, fully justified by the somewhat amusing circumstance, that the critics are unable to agree among themselves as to the exact logical place of any of the series. While one insists that Logic should be placed in Philosophy, he is bound to admit that it ought not to be separated from Mathematics, while on the other hand he cannot allow arithmetic, book-keeping and geometry to invade the sacred temple of the philosophers. Education is even a greater stumbling-block. It is variously assigned to Psychology, Sociology, Philology and Ethnology by different critics, and Fine Arts is equally perplexing. In actual practice in a library, there is really no inconvenience felt in connexion with the distribution of any of these classes, and as they do not originate naturally from any of the other main divisions, but qualify and pervade the whole of them like an encyclopædia, or other general work, it will be found best to retain them where they are. The other important features of this system are described below.
The Categorical Tables form an important feature, whereby a separate series of forms, phases and other qualifying factors are provided, which can be applied to every subject, and so relieve the main tables from congestion. They are applicable to the very largest libraries, and give ample means of subdividing any topic, however large it may be. They can also be used with other systems of classification, as they are independent of the main tables and form a series of parallel numbers by which the classification numbers can be themselves classified. For example, a library may have 1000 books on a subject like Architecture in general, to all of which the simple number B300 would be applied. By adding the qualifying numbers from the Categorical Tables, which appear after a point, and are invariably the same when applied to any subject, the following sub-classification would result, which has the effect of assembling all related forms of books together:
| B300 | Architecture, | General | |
| B300·1 | — | Bibliography | |
| B300·2 | — | Dictionaries | |
| B300·3 | — | Text-books, | Systematic |
| B300·4 | — | — | Popular |
| B300·6 | — | Societies | |
| B300·7 | — | Periodicals | |
| B300·10 | — | History | |
and so on.
If, in addition to those general works, the library possessed several hundreds of books on Building Construction, B305, these would be subdivided in exactly the same manner, as would also any subdivision of the same topic, such as Foundations, Walls, Roofs, etc.:
| B305·1 | Building | Construction, | Bibliography |
| B305·3 | — | — | Text-books, Systematic |
| B305·10 | — | — | History |
| B329·1 | Roofs, Bibliography | ||