If it is deemed helpful punctuation to set off by commas the group of words between “books” and “are,” in order to show clearly the dependence of “books” upon “are recommended,” then commas are required. If, on the other hand, we wish to show by the punctuation that the group of words following “books” is restrictive, we must omit the comma after “books.” Thus, apparently, we must here make a choice between two modes of punctuation. As failure to distinguish by punctuation the character of a qualifier,—that is, whether restrictive or explanatory,—not infrequently totally obscures the sense, we do not quite like a rule that calls for a comma before a restrictive group of words.
The sentence may be written without a comma after “books,” but with one after “professors.” The use of the latter would follow the punctuation of No. 79. This mode of punctuation is, after all, only a choice between two modes of punctuation. The better way is to recast all such sentences. No. 84 may be recast in several ways; but it is difficult, without introducing a new word, clearly to express the fact that one kind of books is meant, as shown in the restrictive adjective in both Nos. 84 and 84-1.
We suggest the following form for the recast sentence:
84-2. When certain books have been thoroughly examined and unqualifiedly approved by a board of college professors, and have been recommended by a teacher, her pupils should not refuse to read them.
Every restrictive word or group of words confines the meaning of the word or words so modified to a certain thing or certain things. The man who was here yesterday means a certain man, and means so because of the restrictive group of words following “man”; but “the man, who was here yesterday,” is not so designated by the same group of words set off by commas. These points were considered in another place in this book.
NOT—BUT
The punctuation of intermediate groups of words gives rise to a peculiar phraseology, which needs explanation. We have seen that the intermediate group is set off by commas to show that the sense is suspended at the point where the first comma is placed, to be continued by connection with what follows the complementary comma. We illustrated this process diagrammatically in Sentence 4-3 by actually suspending on the printed page the intermediate group.
We do not hesitate to use commas in the following sentence:
85. His success was attained, not by ability and enterprise, but by friendly assistance.
If we suspend or omit the intermediate group in the above we obtain a result which is not a good sentence: