In this sentence one college (William and Mary) is named by a group of words connected by “and,” this group being followed by another name also connected by “and” to what precedes. All punctuators admit that such grouping imperatively demands a comma before the final “and,” for without the comma the reader could not possibly ascertain from the language the names of the colleges.
As such grouping is very common, and as the tendency to group together words connected by “and” is quite natural, the use of the comma before the final “and” in every series is helpful punctuation. This punctuation makes the absence of the comma before “and” give notice that a group of words within, and not at the end of, the series, is reached. For this reason it is well to make the punctuation of every series uniform.
This punctuation requires a comma before “and” in No. 8-1:
8-3. William, Henry, and James are at school.
Unless one, in reading aloud, exhibits the grouping by voice-inflection, his hearers may not comprehend the meaning conveyed by the grouping. Failure thus to show the grouping in No. 8-2 would utterly confuse the hearer as to the names of the two colleges designated by a group of words in which two “ands” appear. This relation between voice-inflection and punctuation is considered in our discussion of Sentence 28 and its variations.
A possible and apparent exception to the punctuation exhibited in No. 8-3 may be demanded in the punctuation of a very familiar group of words, the address line of a speech:
8-4. Mr. President, Ladies and Gentlemen.
The voice-inflection of almost every speaker who uses these words, as well as of almost every person who reads them aloud, exhibits a grouping that inhibits the use of a comma before “and.” In other words, the people addressed by the speaker are divided into two groups,—the “president” constituting one group, and “ladies and gentlemen” another. This grouping is exhibited by the voice-inflection of the speaker or reader and by the omission of a comma before “and” by the printer.
If, on the other hand, three groups are to be made of the persons addressed, the voice-inflection and the punctuation (a comma before “and”) should show the grouping.