Let’s keep to the topic of punctuation and consider how parentheses differ from commas. In another post (Punctuating the Parentheses), we saw that parentheses enclose words that can be meant to stand with, but not directly on, the loadbearing grammatical foundation of a sentence. The parentheses in the sentence I just wrote, for example, created space for something else I wanted to tell you (namely, the title of the earlier post), but by using parentheses instead of commas, I was suggesting that, oh, by the way, here is the actionable information you might need should you wish to consult the post I’m referring to. You don’t need this information to understand the sentence, but here it is as a courtesy.
Think of parentheses, then, as building an addition to your sentence. The information they make room for is certainly a part of the larger statement (or you would not otherwise be including it), but if you deleted the parenthetical matter entirely, the grammatical foundation would remain intact. This, though, is English grammar we’re talking about, and so the subject is not quite that simple. If you look again at the second sentence of this paragraph, you’ll see that the information in that set of parentheses is more closely related to the foundation of the sentence than was the case in the first example we examined. The clause or you wouldn’t otherwise be including it contains a pronoun, it, whose antecedent lies beyond the parenthetical boundaries. The word it is referring to the noun information, and that grammatical connection—one element within parentheses and the other without—shows that the parentheses are serving not just to isolate raw data, but to say something relevant more restrainedly.
What is the difference, then, between parentheses and commas? Parentheses can be used to isolate information from the grammatical construction of a sentence, commas cannot. That is why placing the title Punctuating the Parentheses within commas in the first example would not have been correct. In the second example, I could theoretically replace the parentheses with commas, but in doing so I would also have to elevate the comma before but to a semicolon, thereby changing the tone of the sentence entirely: The information they make room for is certainly a part of the larger statement, or you would not otherwise be including it; but if you deleted the parenthetical matter entirely, the grammatical foundation would remain intact. Without this change from comma to semicolon (a common error), the three commas would imply to the reader that the four sections of the sentence all worked together evenly: The information they make room for is certainly a part of the larger statement, or you would not otherwise be including it, but if you deleted the parenthetical matter entirely, the grammatical foundation would remain intact. That is a confusing jumble of ideas which either parentheses or a semicolon can conclusively organize.
It is a mistake to think that punctuation is a small matter in writing. The few marks we have are an attempt to regulate the flow of ideas in the written word as we do with our breath in the spoken word. And while it is not always true, as many of us learned in school, to put a comma where you breathe, that adage does point to the fact that simply stringing words together will not produce a clear statement of our ideas. Writers are writing and readers are reading expository prose with their rational mind, which means ideas take their place in a hierarchy, some more relevant in a sentence than others. The various levels of punctuation, from commas through semicolons to parentheses, help make those important distinctions—and making distinctions is what clear thinking is all about.