One of those questions that are often asked

A friend passed on to me one of those grammar questions that are often asked and often opined on:

In a sentence like “She is one of those people who are always late,” I learned to cross out prepositional phrases when linking subject to verb, so I would cross-out “of those people” and link “she” with “is” instead of “are.” Isn’t “of those people” modifying “one” (which acts as a complement to “she”) and not acting as the actual subject?

The problem with just crossing out preposition phrases is that you sometimes miss where the phrase ends – or doesn’t end! There are a few ways to look at it. The bracket way is short but benefits from further explanation:

She is one [of those people {who are always late}].

What that means is that there are people who are always late, and she is one of them. Yes, “of those people” is modifying “one,” but “who are always late” is modifying “of those people.”

A person could object (as many do) that it could equally be

She is one [of those people] [who is always late].

In other words, of those people, she is one who is always late. The problem with that is only in part that “She is one who is always late” is a bit odd; after all, “She is one” is a bit odd by itself too, but we’re not saying it by itself. The issue is really with “of those people.” For one thing, if the “always late” isn’t there to describe the set of “those people” of which she’s a member, it’s not specified who “those people” are. Who are they? And why are we mentioning them at all? Let’s look at a similar structure:

She is an eater of those hot dogs that have fallen on the floor.

She is an eater of those hot dogs that has fallen on the floor.

The difference is plain enough: in the first, the hot dogs have fallen; in the second, she has. And we have to assume that which hot dogs “those hot dogs” are has been established or can be inferred contextually; if not, it may be perplexing.

She eats those hot dogs. She has fallen on the floor.

Umm… tell me which hot dogs.

Returning to the example in question, the “is” version means this:

She is one of those people. Specifically, she is one who is always late.

If you’re in a context where you know who “those people” are, OK; but otherwise you have to specify them, or why are you mentioning them? And if your answer to “Who are they?” is “People who are always late,” you have shown why you really want to say “those people who are always late.” If she is one of them, then yes, she is one who is always late (as are they all), but if you go with the “is” version then you haven’t actually specified who they are; in fact, you’ve implied they’re not all like her in this respect. It’s like saying

It’s one of those hot dogs that is delicious.

You can see that the implication is that not all of those hot dogs are delicious; otherwise, why would you be singling that one out? Or if you say

He’s an editor who is popular at parties.

you know that it implies that not all editors are! And likewise, if she is one of those people who is always late, by implication others of those people are not. On the other hand, if you say “one of those people who are” and she is one of them, then she is covered.

That’s the logical analysis, and it’s the one I go with as an editor. In casual speech, I admit that I sometimes say “who is” in similar instances before I can catch myself, just because the structure of the sentence is so analogous to others where “is” would be appropriate; “one of those people” is a noun phrase like “a member of the club,” and we would most likely say “She is a member of the club who is always late.” (Unless it’s a club of people who are always late. Which is, in fact, what we mean in this case!) But when I’m editing, it’s more important to make it stand up to analysis. And it sounds good to me.