CJR's "Language Corner"

Columbia Journalism Review has a page called the Language Corner, which offers (or should I have said "that offers"?) "various rules of the language, including rules of thumb..." It looks interesting and useful. Excerpt:

Why use “that” in one place and “which” in another? Well, consider:

The cars that were green failed to run.

In that sentence, "that were green" is a restrictive, defining, or (the favorite here) essential clause.

It’s essential because without it, we have “The cars failed to run” — not at all what we set out to report. Orange cars, say, may have hummed right along; it’s green cars that didn’t. Now consider:

The cars, which were green, failed to run.

Take out the clause, and the intended meaning of the sentence remains: the cars — all the cars we’re discussing — failed to run. Their color is incidental, not essential.

The principle is the same even if the content of the (nonessential) “which” clause is exciting:

“The pistol, which was the murder weapon, was a Mauser.”

For the purpose of the sentence as it's structured, what is essential is not what the pistol was used for but who made it. (The commas are characteristic around “which” clauses but not “that” clauses.)

Does that/which matter? Writers of the British school seem to use “which” routinely in both kinds of clauses, even though their great mentor, H.W. Fowler, favored a distinction. For Americans, the “rule” is worth understanding not because it’s intrinsically sensible — it’s not — but because many teachers and editors insist on it.