Three Problems of Nonparallel Interjections

Three examples of more complex errors involving corresponding sentence elements.

1. “Low-interest rates have been one of the primary, if not the primary factor in extending the real estate boom in the United States.”
The corresponding phrases in this sentence are neither parallel nor complete. First, the additional consideration (“if not the primary factor”) must be structured as an interjection, meaning that it has to be bracketed parenthetically by commas, em dashes, or parentheses. (Which method you choose depends on the emphasis you want to give the interjection: Parentheses minimize the interruption, commas are the default punctuation for separating an interrupting phrase from the main sentence, and em dashes call attention to the inserted phrase.)

In this case, “if not the primary factor” must be set off from the rest of the sentence with punctuation before and after; any of the three punctuation forms is appropriate. However, there’s more work to be done. The key to correctly constructing a sentence with an interjection is that if the interjection is omitted, the sentence is still complete.

But read this version of the sentence with the interjection omitted: “Low-interest rates have been one of the primary in extending the real estate boom in the United States.” Obviously, factors must be inserted after the first use of primary in additional to the inclusion of the singular form of the word in the interjection: “Low-interest rates have been one of the primary factors, if not the primary factor, in extending the real estate boom in the United States.”

2. “Talk of a name change has struck some political observers as not only a merely cosmetic, but also as a pointless gesture.”
As with the previous example, this sentence lacks a correctly framed interjection — “but also as a pointless” must be set off from the rest of the sentence: “Talk of a name change has struck some political observers as . . . a merely cosmetic gesture.” (The ellipsis marks the omission of “not only,” which as part of the “not only . . . but also” comparative device is technically a part of the interjection.)

The corrected sentence should read, “Talk of a name change has struck some political observers as not only a merely cosmetic, but also a pointless, gesture.” (Note the omission of the second instance of as.) Better yet, convert the interjection to a sentence-ending tag: “Talk of a name change has struck some political observers as not only a merely cosmetic gesture but also a pointless one.”

3. “He could have, but he didn’t, press for a clear, bilateral agreement on immigration.”
Use the interjection-omission test described above to analyze this sentence’s problem: Without the (correctly punctuated) interjection, the sentence erroneously reads “He could have press for a clear, bilateral agreement on immigration.” A hypercorrection featuring logical correspondence at the expense of readability is “He could have pressed, but he didn’t press, for a clear, bilateral agreement on immigration.” As with the previous example, the sentence is best repaired by moving the interjection to the end of the sentence: “He could have pressed for a clear, bilateral agreement on immigration, but he didn’t.”