Casagrande: The double positive is a respectable English idiom

“Any friend of Henry’s is a friend of mine.”

You’ve probably heard variations on this sentence a hundred times, at least. It’s a nice tribute to Henry — the idea that he’s so cool or honorable or kind or charming that it somehow extends to everyone he befriends.

But have you ever thought about the grammar? This sentence contains a grammatical problem — not an error, exactly, but a fault in the syntax few of us are likely to notice. It’s called a double possessive. And the handful of people who are aware of it often think it’s wrong.

“The double possessive is redundant and should be avoided in careful speech and formal writing,” advised a legal journal in the 1990s.

What, exactly, is the redundancy? It has to do with the word “of.”

You see, “of” can create a possessive all by itself. That is, “a friend of Henry” is already possessive. So when you add the apostrophe and S to Henry, making it Henry’s, you’re making the phrase possessive twice. After all, “Any friend of Henry is a friend of mine” means the same thing as the version with “Henry’s.”

But that doesn’t mean the double possessive is wrong. In fact, though sometimes the apostrophe and S are unnecessary, other times it makes sense to use them.

“The double possessive, usually using both ‘of’ and ‘‘s’ to demonstrate possession, is grammatical. While it is sometimes unnecessary, it can be helpful for differentiating between when the possessive (or genitive) case is about association or when it’s about ownership, such as in ‘a picture of my friend’ vs. ‘a picture of my friend’s,’” writes Merriam-Webster’s online dictionary, adding that the double-possessive has been in use since Chaucer’s day.

Part of the reason it’s OK has to do with how “of” works in structures like these. Yes, “a friend of Henry” clearly shows possession, but, as we saw in the example above, “a picture of Henry” does not. So because “of” has multiple jobs, it’s not always clear when it’s meant to show possession. And when it’s unclear, an apostrophe and S can help.

But to my mind, the most interesting argument in favor of the double possessive is evident when you replace nouns like Henry with their pronoun forms.

Would you say “a friend of him,” which uses a nonpossessive pronoun, or would you say “a friend of “his,” which uses the possessive? How about “a friend of me” vs. “a friend of mine,” or “a friend of us” vs. “a friend of ours”?

Clearly, the possessives are necessary here.

Merriam-Webster isn’t the only authority that says this double possessive is OK.

“Some people erroneously stigmatize ‘a friend of mine’ or ‘an acquaintance of John’s,’ in which both an ‘of’ and a possessive form appear,” notes Garner’s Modern American Usage. But in fact, the guide says, “Using both the s- and of- genitives together is an English idiom of long and respectable standing.”

The Chicago Manual of Style, however, puts their own spin on it: “The possessive form may be preceded by ‘of’ where one of several is implied. ‘A friend of Dick’s’ and ‘a friend of his’ are equally acceptable.”

Personally, I feel this leaves unresolved the question of nearly identical structures that don’t mean one of several, like “That darling mother of yours” and “Those wonderful parents of yours.” Neither of these means “one of several,” yet they both work better with the possessive “yours” than the not-possessive “your.”

If you like a mathematical precision to your language, you can opt for nonpossessive forms whenever they work: “a friend of Henry.” But when a possessive works better, don’t hesitate to use it.

— June Casagrande is the author of “The Best Punctuation Book, Period.” She can be reached at JuneTCN@aol.com.