Let us first ask why any mark is required before “and” in the sentence, and then what the mark, if used, says to the writer. When the reader reaches the conjunction, two questions at once confront him: First, does “and” connect the words between which it immediately stands? second, does “and” carry the if meaning over to the second group of words? As “and” does not connect the words between which it immediately stands, some mark is suggested; and that mark is the comma, but a comma may not clearly exclude if from the second group. If the if meaning is not to be conveyed, a larger grouping is suggested; and this would call for a semicolon, which would more widely separate parts (subject and predicate) of the whole sentence which should be held together.
The and relation is here what we may call a strained one; in fact, the and relation hardly exists in this sentence.
The punctuation of No. 67-1 is all right if we accept a meaning of the term parenthesis that will cover the group of words we are here dealing with; but the punctuation is wholly wrong if we use marks according to fundamental principles. Both the New International and the New Standard dictionaries give definitions of a parenthesis that are incomplete and misleading. Their definitions are almost identical in their wording, and call a parenthesis, in substance, a group of words inserted, for explanation or qualification, “in a sentence which would be grammatically complete without it.” This definition ignores both the root meaning of the word and the common usage of the parenthesis. It is an excellent definition for an explanatory word or group of words, except a complete explanatory sentence, which we set off by commas, as shown in our discussion of Sentence 11 et seq. We do not know what would become, under this definition, of a parenthesis in the form of a complete sentence; for the definition confines the parenthesis to a word or words inserted in a sentence.
The Century gives a definition that is based upon the Greek roots of the word parenthesis, as well as upon its use by good writers. According to this definition, a parenthesis has no grammatical relation with the language into which it is “put.” (The word thrust would perhaps give a clearer idea of the original.) We “parenthesize” in spoken, as well as in written or printed, language; but in the former we convey the meaning by inflections and pauses, while in the latter we convey the meaning by marks of punctuation.
The use of the conjunction (and) in the sentence under consideration clearly takes the inserted group of words out of the proper definition of a parenthesis; for it puts such words into grammatical connection with what precedes, although the words are quite strongly parenthetical in nature.
Now, having eliminated the comma, the semicolon, and the parentheses as the proper marks for setting off this group of words thrust into the sentence, and still making good sense by their grammatical connection, how shall we punctuate them? It is perfectly evident that this group of words makes a decided break in the thread of the thought, and that they do not have logical or natural connection with what precedes, because the true and relation does not exist between the thoughts, implied or expressed. Such language may be said to be idiomatic and therefore proper; but the group of words is not properly set off in either No. 67 or No. 67-1. As the fundamental use of the dash is to note such a break in language as here occurs, it is the proper mark before “and” in this sentence. In language of this kind it may be said that the writer dashes off the track of his thought for a moment; and therefore the dash is the proper mark to indicate such a break in the continuity of thought.
The second dash is used to close the group in the same way that the second comma of a pair of commas, or the second part of the marks of parenthesis, is used; and this makes the punctuation of No. 67-2 correct punctuation, for it is based upon the fundamental meanings of both the marks and the sense relations of the words.
This careless use of the marks of parenthesis, especially as in No. 67-1, is quite common in some literary periodicals of high standing and in not a few large printing establishments; but, we venture to assert, it is rare among painstaking writers who punctuate their own writings.
Such use of marks utterly prevents a differentiation between commas and parentheses; and this disregard of sense relations finds an exact parallel in a disregard, only too common among careless writers, of such fundamental differences in meanings as exists between the words vocation and avocation.
Let us also note that groups of words defined in Chapter III as “slightly parenthetical” do not make any break in the thread of thought, so that Sentence 67 is not at all similar to such sentences as were considered in that connection. In further proof of this statement, let us compare Sentence 67 with Sentence 10-2. If the and relation in No. 67 does not exist between the two groups of words (all that precedes it, and what follows it up to “is”), the group “I have no doubt” should be set off by commas, as is a similar group in Sentence 10-2. This punctuation would make “and” connect “be” and “it is,” which would not make sense.