My friend Aaron had a question about a comma. In a sentence like the following, would you keep the second comma or ditch it?
"The participants included a delegation of civic leaders, including the influential developer Ellis Bradley, who had been advocating infrastructure projects since the late 1990s."
A reader isn't likely to notice the punctuation in this sentence. But a cautious writer just might observe something: The second comma raises the possibility that the "who" clause is modifying "civic leaders," not "Ellis Bradley."
Here's a simple sentence in which that's exactly how the commas work.
"We heard a speech by Stacey Lewis, held in the auditorium, who drew raucous applause."
The "who" clause clearly refers to Lewis. She's the only "who" in the sentence. But there's some parenthetical information separating her name from that clause in this (admittedly bad) sentence.
Aaron's sentence could be construed to work the same way, with the clause "who had been advocating infrastructure projects" referring to civic leaders instead of Bradley.
Yes, the risk of reader confusion seems low. But it's worth asking whether that risk can be eliminated by omitting the comma.
Turns out, that creates a worse problem: a restrictive clause the writer didn't intend.
Restrictive clauses narrow down the scope of a noun. Compare: "the man, who had a gun" with "the man who had a gun."
In the second one, the "who" clause limits the scope of the noun "man." "The man who had a gun" is more specific than just "the man." It tells you which man we're talking about.
A comma changes things. "The man, who had a gun" presumes you already know which man we're talking about. The comma is key.
Take out the comma out of Aaron's sentence and you're cueing the reader that the "who" clause is essential to knowing which Bradley we're talking about, as if there are multiple Bradleys in question so you need to know we're talking specifically about the Bradley who advocates infrastructure projects.
To me, that's a serious grammar problem. It outweighs the concern that readers might misconstrue the correctly punctuated sentence.
By the way, "who" and "whom" clauses, along with "that" and "which" clauses, make up a category known as relative clauses, which modify nouns.
In, "The book that I was reading," the "that" clause tells you more about the book, a noun.
Relative clauses can be restrictive or nonrestrictive — a role often aided by commas.
Similar to our gun-toting-man example, "the book that I was reading" and "the book, which I was reading" are different.
Again, the restrictive "that" clause specifies the exact book we're talking about. The nonrestrictive "which" clause suggests you already know which book I'm talking about. The fact that I was reading it is just extra detail.
Style guides forbid using "which" clauses restrictively. In AP and Chicago styles, it's an error to write "The book which I read last week was better than the book which I'd read last month."
But that's a style rule, not a grammar rule. Use your ear to decide which "whiches" work best.
Relative clauses aren't the only parts of speech that can be restrictive. Other elements can, too — usually aided by commas.
"The book 'Misery' was made into a movie." The book title "Misery" is a noun. Yet in this sentence it's clarifying the meaning of another noun, "book."
It's telling us which book is "the" book. So the title "Misery" in this example is a restrictive noun phrase.
Compare that to "The book, 'Misery,' was made into a movie." The commas are your cue that the title is just supplemental info. Presumably, the reader already understands there's just one book we might be talking about.
Noun phrases, participial phrases, adjective phrases and many other parts of speech can narrow down the scope of a noun they modify.
In other words, they can all be restrictive. Commas are always the tip-off.