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That and Which: Which is Which?

Frances Peck
(Terminology Update, Volume 34, Number 4, 2001, page 20)

"To this day I cannot be sure when I should use ’that’ and when I should use ’which,’ but my secretary knows, and between us we keep up some sort of pretence." So admitted the venerable Robertson Davies in 1978.

Davies is but one example of the legions of writers—not to mention ordinary, non-authorial folk—to confess themselves befuddled by these deceptively innocuous pronouns. Little wonder, when language experts themselves can’t agree. Over the past century, few topics have ruffled more feathers in the linguistic aviary than that and which, with language pundits squabbling over whether the distinction is real or bogus, enforceable or laughable.

The Convention

Leaving for a moment the rich historical debate, let’s look at the that/which rule—or convention, as we might more accurately call it. On the surface, it is relatively simple: use that to begin a restrictive clause and which to begin a non-restrictive clause. But in reality, many writers have as much difficulty differentiating between restrictive and non-restrictive clauses as they do sorting out that and which.

A non-restrictive clause does not restrict or limit the meaning of the word it describes. It helps to think of a non-restrictive clause as non-essential. It interrupts the main point of the sentence, adding extra "by the way" information that is interesting but not really necessary. Here are some examples:

  • His father, who was a tax accountant for thirty years, now runs a psychic hotline from his cottage in the Muskokas.
  • Even now I miss Hillsdale Elementary, where the most valuable lessons unfolded in the schoolyard.
  • Lunch, which was served at 12:30 sharp, consisted of codfish hash, beet greens and boiled tea.

Notice that in all three cases, the non-restrictive clause can disappear from the sentence without affecting the main idea. To signal that a non-restrictive clause is merely an interruption or elaboration, you must set it off with a pair of commas—or one comma if, as in the second example, the clause appears at the end of the sentence.

Notice also that the clause in the third example begins with which, not that, since which is the proper pronoun to begin a non-restrictive clause.

A restrictive clause, on the other hand, is just the opposite. It restricts or limits the meaning of the word or words it describes. No mere interruption or interjection, it provides information that is essential to the main idea. A restrictive clause often defines what it describes, as in these examples:

  • Ottawa residents who do not hold secure, well-paying jobs must resent the city’s portrayal as a land of opportunity.
  • We cherish warm memories of our fellow alumni who are dead.
  • Years ago I painted a picture of the deserted farmhouse that burned down last week.

In all three sentences, the restrictive clause is essential to the main meaning, defining which Ottawa residents must feel resentful, which fellow alumni evoke warm memories, which deserted farmhouse I painted a picture of. To show that the clause is necessary, you must run it into the sentence, without commas.

Punctuation skeptics may scoff, but the presence or absence of commas around descriptive clauses is not some finicky bit of window-dressing, nice for the interested few but hardly necessary for the rest of us. On the contrary, commas can radically affect meaning. Imagine commas around the restrictive clause in the first sentence above. Suddenly the main idea becomes Ottawa residents must resent the city’s portrayal as a land of opportunity—oh, and by the way, Ottawa residents do not hold secure, well-paying jobs. A comma before the clause in the second sentence wreaks similar havoc with the sense. Now the main idea is We cherish warm memories of our fellow alumni—who, sorry to say, are all dead.

Notice that in the third sentence, the restrictive clause begins with that, not which. Those who observe a distinction between the two reserve that for restrictive clauses and which, as we’ve seen, for non-restrictive.

The Controversy

Why is this modest principle the subject of so much grammatical hand-wringing?

The which part of the convention is largely beyond dispute: all reputable language guides and authorities stipulate that which must begin a non-restrictive clause. The disagreement centres on that. The fact is that to many ears, Years ago I painted a picture of the deserted farmhouse which burned down last week sounds just as correct and natural as Years ago I painted a picture of the deserted farmhouse that burned down last week. Many people, including countless professional—indeed, award-winning—writers use which and that interchangeably to begin restrictive clauses, basing their choice more on sound and rhythm than on an ironclad rule. And they have done so for centuries.

It is difficult to pin down exactly when the that/which question took root in English grammar. Some finger H.W. Fowler as the "inventor" of the rule. After all, he wrote about it in 1906 in The King’s English, and later in his hugely influential Modern English Usage. But it is probably more accurate to say that Fowler popularized the notion, since earlier language scholars advocated the same distinction.

Regardless of its provenance, the that/which distinction has attracted both stalwart advocates and steadfast foes. With two factions to choose from, what’s a person to do?

The Bottom Line

Bear in mind that the one incontrovertible rule concerns the punctuation: commas around a non-restrictive clause, no commas around a restrictive. If your clause is non-restrictive (and therefore introduced by a comma), use which rather than that—remember, there’s no debate there. If your clause is restrictive (with no commas), you can choose sides. If you want to observe the distinction, use that. If not, use whichever pronoun sounds better.

That said, in casting your support, you should know that most modern grammar and usage texts advocate the that/which distinction, particularly for formal, non-literary writing. Most Canadian editors (outside literary editing) follow the principle, as do many careful writers. If you go that and which hunting, you’ll find yourself in excellent company.