Uniting the second and third sentences by a semicolon will improve the grouping and the punctuation; but making one sentence out of the three is still better:
18-1. Milton does not paint a finished picture, or play for a mere passive listener: he sketches, and leaves others to fill up the outline; he strikes the key-note, and expects his hearers to make out the melody.
The relations between the groups may be shown in another way; but such mode of expressing thought is not tolerable:
18-2. Milton does not paint a finished picture (he sketches, and leaves others to fill up the outline), or play for a mere passive listener (he strikes the key-note, and expects his hearers to make out the melody).
CHAPTER VIII
COMMA, DASH, AND PARENTHESES—THEIR DIFFERENTIATION
We know of no writer who has attempted to differentiate the above marks; but some writers have dismissed the subject by saying that these marks are interchangeable. Such a statement, we believe, is merely a confession of failure to comprehend the inherent meanings of the marks, and the need of giving marks definite meanings. The confusion resulting from such failure is, at least at this point, chaos in punctuation and, not infrequently, in the meaning of language so punctuated.
Mr. Garrison,[7] in his able Atlantic article, says: “Dash, comma, and parenthesis have equal title to employment in this sentence of Thackeray’s.” The following is the sentence punctuated in the three ways recognized by Mr. Garrison as correct punctuation:
67. If that theory be, and I have no doubt it is, the right and safe one.
67-1. If that theory be (and I have no doubt it is) the right and safe one.
67-2. If that theory be—and I have no doubt it is—the right and safe one.