The Essence of a Clause

In casual reading of OPW (Other People’s Writing), I’ve been known to let “its”/”it’s” and “your”/”you’re” slide.

(Increasingly so, because the cause is starting to seem hopeless.)

But the one I can’t let go–the mistake that bothers me most–is the bungling of that and who.

“I’m the kind of person that complains about other people’s grammar mistakes while making tons of my own.”

“Only readers that have the perfect mix of gullibility and four or more credit cards qualify to buy this product.”

No. People WHO. Gullible readers WHO!

That isn’t the topic today, though.

(It will be one day soon. And there will be blood.)

Today we’re looking at something closely related: That versus which, and the scary, dark, churning river that runs beneath them:

Essential clauses and nonessential clauses.

My reading this afternoon comes from The Associated Press Stylebook:

“Both types of clauses provide additional information about a word or phase in the sentence.”

No problem. We’re writing about X. There is more to say about X. Why start a whole other sentence to say it?

“The difference between them is that the essential clause cannot be eliminated without changing the meaning of the sentence — it so restricts the meaning of the word or phrase that its absence would lead to a substantially different interpretation of what the author meant.”

So the key is whether not saying the additional thing we want to say about X would irreparably damage the information.

I have two cats: A tuxedo, and a six-toed tabby.


One day I leave to get the mail, and when I come back my tea is spilled:


I come to a fast conclusion about what happened, based on past knock-overs. 

“The cat that has the long whiskers and the bow tie on his face did this.”

The whiskers and bow tie are essential to my accusation. They’re how I identify the culprit. Essential clause. And I identify it as such with “that”.

Let’s go back to the text:

“The nonessential clause, however, can be eliminated without altering the basic meaning of the sentence — it does not restrict the meaning so significantly that its absence would radically alter the author’s thought.”

So returning to the scene of the crime, I further conclude that:

“The six-toed cat, which is too lazy to cause any trouble, has been napping on the armchair all day.”

Maybe this isn’t a perfect example. But the fact that the innocent cat is historically too lazy to cause any trouble isn’t essential to my point.

It’s nonessential. So, “which”.

The necessary part is that I believe he’s been on the armchair all day and therefore couldn’t have made the mess.

So I scold the tuxedo, clean up the mess, and get on with things.

Later I check the security camera reel and see the truth:


My house is a house of false accusations.

There are two other interesting points here: One about how comma placement can affect a clause’s essential-ness. And one interesting addendum about “who” vs. “that”, as they relate to “an inanimate object or an animal without a name.”

I think we’ll revisit this in two weeks.

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