It always seems to be about the comma. What does this sentence mean, do you think: Be sure you peel the oranges before juicing; the rinds contain oils, which can cause an upset stomach. The first purpose of a comma is to separate. The word comma itself comes from a classical Greek word meaning to cut off, so when we see or write a comma, we should be thinking about how and why some element is being isolated from the words around it. Understanding this is not just a matter of style alone; it can also change the meaning.
The sentence we are analyzing is composed roughly in halves, the two sections separated neatly from each other by a semicolon (more on that later). The first half of the sentence is made up of one clause (be sure), and tells us what to do; the second half comprises two clauses, the first an independent clause (the rinds contain oils) and the second a subordinate clause (which can cause an upset stomach) which depends on the independent clause before it to make sense. Importantly, these two clauses in the second half of the sentence are separated by a comma.
Why? Because the author apparently means to say that oils—all oils—can cause an upset stomach. Now you may jump up from the table, brandishing a bottle of fine Italian olive oil, and object that such a statement cannot possibly be true, but that is what the comma in this sentence forces us to conclude. Remember, commas separate, and so the comma before which has separated that relative pronoun from its likely antecedent (oils), which means which now refers to the previous clause in its entirety (the rinds contain oils), not just the word oils. It’s quite an assertion to make.
Now if it is true that some oils, but not all, can upset the stomach, and that the rind of an orange contains a few of these offending oils, then some attempt must be made to limit or restrict the meaning of oils in this sentence in order to avoid the obviously indefensible contention that all oils cause an upset stomach. We limit or restrict the meaning of a word by abutting another element to it, by causing one element to touch another—without the intermediary of a comma. So the way to restrict the meaning of oils is to adjoin the which-clause directly to it: the rinds contain oils which can cause an upset the stomach. This has the effect of defining the kind of oils orange rinds contain—the kind that can upset the stomach—and it tones up the sentence by making it more logically precise. In exactitude lies strength.
The rule to remember, then, is that commas separate. When elements are set apart, each stands alone and can be rightfully held accountable for what it alone is saying—no help to qualify its meaning can be taken from another element because the comma has isolated it. Removing the comma in our example restores the word oils to the community of ideas that the complete sentence represents, putting it in touch with the qualifying assertion that follows it. The razor-sharp comma, so useful at times, can rip things apart if not wielded carefully.
As to that semicolon that separates the two halves of the sentence, note that it is standing in place of the conjunction because: Be sure you peel the oranges before juicing because the rinds contain oils. This is one of the most important functions of the semicolon, to take the place of an omitted conjunction, and a very common mistake is to use a comma here instead of the semicolon (producing the famous run-on sentence). If commas separate, semicolons separate and pause, which is just what is wanted at this point in the sentence in order to establish a balance and steady the reader halfway through the sentence. Punctuation is an integral part of composition, and the choices we make determine exactly what we’re saying.
Because of the holiday, this Thursday’s post will appear Friday. Happy Thanksgiving—and my thanks to you for reading Writing Smartly.