That which does not kill me …

I recently heard that someone had been advised against ever using the word ‘that’ in their writing. Editors are often asked to clarify rules for people who were terrorised at some point in their education about prepositions, pronouns and prose, but this one was new to me. ‘That’ has many functions in English, so many that I felt anyone trying to speak or write without it would come across as if the reception were breaking up.

‘That’ can be all kinds of trouble to a writer because it can function as:

  • a demonstrative adjective (you’ll see in that magazine)
  • a demonstrative pronoun (hey, look at that!)
  • a relative pronoun (I had dinner at the restaurant that everyone was raving about)
  • a conjunction (we know that she is in cahoots with him)
  • an adverb (she was that mad!)

It turns out that the advice was about preferring ‘which’ over ‘that’ in the case of relative pronouns, under the assumption that the former was more correct in writing, and the latter should be reserved for speech. This idea was described as ‘a supposed, & misleading, distinction’ by Fowler in 1926. He explained the different frequency of their use as evidence of more complex structures in writing, where more peripheral information is packed into a single sentence, than is usual in speech, where people tend to keep sentences simple and add information by making new sentences.

The most common problem with that/which is in defining versus non-defining relative clauses. Consider these two sentences:

The women in my class, who are doctors, are left-handed.

The women in my class who are doctors are left-handed.

Non-defining clause

The first of these is an example of a non-defining clause. That is, the part in the middle that is set off from the rest by the commas does not ‘define’ the first part. It’s just an extra piece of information. My main statement is that ‘the women in my class are left-handed’. As it happens, they are also all doctors. Non-defining clauses are always set apart from the main clause by a pair of commas.

Defining clause

The second example shows a defining clause. In this case, there are some women in my class, but only some of those women, the ones who are doctors, are left-handed.

When you’re talking about people you use the relative pronoun ‘who’. But what if you’re talking about inanimate objects? Then you have a choice between ‘that’ and ‘which’:

Non-defining: The books in my house, which are fiction, are very old.
(can only use ‘which’ here, and the additional information is set off with commas)

Defining: The books in my house that are fiction are very old.
(can use either ‘which’ or ‘that’)

In the first example, my main statement is that all of my books are very old. It happens that they are also all fiction. In the second example, I’m making a statement that only the fiction books in my house are very old.

The rule is that you can’t use ‘that’ for a non-defining clause, but you can use ‘which’ in either defining or non-defining clauses. So in that second example we could have said ‘The books in my house which are fiction are very old’ and it would have meant the same thing. Fowler lamented in 1926 that it would be much clearer if we all agreed to use ‘which’ only for the non-defining clauses and always use ‘that’ for the defining clauses, but it’s just not the way the world is.

After editing many reports with complex sentences that contain relative clauses, which can make a sentence long and unwieldy, I agree with him completely.

References and other sources

Fowler HW. 1926. A Dictionary of Modern English Usage (1st ed.). Clarendon Press. Oxford.

Grammar Girl on ‘that/which’

OWL at Purdue on relative pronouns