One of the great English usage wars, and there are many of them,
revolves around the proper use of "that" and "which."
Usage experts, like grammarians, seem to like rules. After all, if
there's a rule, you don't have to think, you just follow it. That works
for teachers, too--teach the rule, and that's that. So usage experts
invent rules, and you're supposed to follow them.
Probably the reigning usage guru in the United States today is
Bryan A. Garner, author of Garner's Modern American Usage
(Oxford, 2003). And Garner absolutely froths at the mouth about the
"that-which" rule--it's follow the rule or die. His book is surely the
best U.S. guide around, and every writer should own it, but, like any
usage book, it's biased.
This particular usage war started around 1880, but it became
intense in the early twentieth century, when H.W. Fowler published
Modern English Usage. Fowler is the greatest usage expert of them
all, revered by the whole corps of usage mavens. His book is
comprehensive, sensible, and, of all things, funny--it's a joy to read.
He approved the rule, and argued strongly for it. Then a funny thing
happened: U.S. writers bowed down and began to follow the rule as
if it were Holy Writ, but in Fowler's home country, nobody paid any
attention. Writers of U.K. English almost always ignore it, and R.W.
Burchfield, the leading English usagist, says that's perfectly okay.
If you're a U.S. writer, you need to know it, so here it is.
The rule is to use "which" for non-restrictive clauses, and "that" for
restrictive. Restrictive means the clauses have to be there for the
sentence to get over the info needed. Non-restrictive means you can
take the clause out and the sentence will still do the job.
Examples:
Three cars stand in the street. One is red, one blue, and the other
yellow.
The car that was red started moving. In this case, it's
restrictive--you need the clause "that was red" to know which car
moved. In this kind of case, use "that."
There is only one car:
The car, which was red, stared moving. It's non-restrictive. Take out
the "which" clause and all the info you really need is there--knowing
the car was red is a plus. In this kind of case, use "which," and
always put a comma on each side of it.
But this rule didn't come down from heaven. Sometimes using
"which" instead of "that" in a restrictive clause simply sounds
better, so it makes sense to use it:
That was illegal, so the car which was red started moving. By using
"which," you avoid using "that" twice in the same sentence. It
doesn't matter much, but some prefer to break the rule in such cases.
On the other hand, using "that" in a non-restrictive clause is always
a mistake:
The car, that was red, started moving. Sounds weird, and it won't
do.
Break the restrictive clause rule--use "which" instead of
"that"--and some people will get all shirty, but if you do it right, it's
fine anyhow. Break the non-restrictive rule and you're in trouble
every time.
There's another case in which "that" causes trouble. If your noun is
preceded by a possessive pronoun, "which" is the way to go.
The wrong way:
"She walked with a book in her arms that were crossed across her
chest."
Much better:
"She walked with a book in her arms, which were crossed across her chest."
In the United States, the safest thing to do is simply follow the rule.
Nobody will complain if you do that.
One other matter requires mention. Try to avoid using either "that"
or "which" when what you're talking about is people. Don't say:
The man that ran down the street. Make it: The man who ran down
the street. That's common courtesy, don't you think? In everyday
speech, people use "that" instead of "who" all the time, but you're
not talking, you're writing, and that's different.
Knowing the rules, which is really not difficult, may not matter
much to you, but it's pleasing readers and editors that gets you
published.
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