Many people take the loose view that grammar and language evolves over time, and therefore you should go with whatever sounds right. Others argue the that/which distinction has basically disappeared. I want to do a comparison to prove once and for all the distinction is necessary. It isn’t preference. They aren’t interchangeable. The meaning of the sentence gets changed by swapping one for the other.
Let me be clear. I am not some obsessive grammar person. I kind of suck at it. But the way people dismiss this point as unimportant and a matter of personal taste (including professional editors!) drives me crazy. It isn’t taste. It’s important.
Many great sources fail miserably in describing the difference between that and which. I’m looking at you Grammar Girl (I love you for everything else) and you Chicago Manual of Style (an excellent doorstop as well). I’m not sure I’ve ever seen a source that gives you the same sentence with “that” and “which” swapped to show the distinction. Everyone has one sentence with “that” to show the use and then a different sentence with “which” to show the use. How is that helpful? It’s like comparing apples to oranges.
Let’s start simple.
Example 1: I played with the marbles, which were blue.
When you use which, you imply that every single marble was blue. This is what is meant by “which is nonrestrictive.” You aren’t restricting your attention to just the blue ones out of a bunch of colors. You’re saying they were all blue. This implication matters. Consider what happens with a simple substitute of “that.”
Example 2: I played with the marbles that were blue.
This sentence has a totally different meaning! “That” implies you have a bunch of marbles of all sorts of different colors in front of you, but you’ve decided to only play with the ones that were blue. This is what is meant by “that is restrictive” or “that is essential.”
Example 3: The puppies, which were cute, ran across the yard.
Example 4: The puppies that were cute ran across the yard.
In example 3, all the puppies ran across the yard. It just so happens they were also all cute. In example 4, only some of the puppies were cute, and only those few puppies ran across the yard. Read these over and over until it makes sense.
Now be horrified at all the times you used these incorrectly and probably implied something you didn’t mean to (did you seriously just imply there are non-cute puppies? Are you sure?). Now look what you’ve done. He’s self-conscious:
Some people argue it’s the comma causing this change in meaning and not that/which. Walk away from that argument. You’ve found someone wrong on the internet, and it isn’t worth your time to engage them. They’re probably a troll anyway. What’s more probable: the distinction made for hundreds of years in a rigorous way still retains some meaning or the words have no meaning anymore and the meaning has magically shifted to comma usage even though the words are still there? Think about it.
I’ve seen a bunch of rules for trying to distinguish between that and which. To me, they’re all pretty terrible. Here’s the easiest rule, which will work 99% of the time.
Step 1: What noun comes before that/which?
Step 2: Does the thing after that/which apply to all of [insert Step 1 answer] or just the ones you’ve described?
Step 3: If Step 2 answer is “all,” use which. If Step 2 answer is “only those described,” use that.
Officially, I wanted to end the post here, but I just know that someone is going to complain I’ve only told you how to tell the difference between that/which when they distinguish between restrictive/nonrestrictive clauses. Not only is the other type of distinction easier, I’m much less concerned with it. Here things can be a bit more stylistic, because the use (often) doesn’t change the meaning of the sentence.
Rule: If you can delete the stuff after that/which without causing confusion, use which. Otherwise, use that.
These examples are slightly harder to give, because they often require context to know if the information is needed.
Example 5: I went to the store, which had roast beef.
Example 6: I went to the store that had roast beef.
If you’re writing a story and there’s only one store. You can delete “which had roast beef” without confusion. The clause “which had roast beef” is inessential. The store just happens to have it. No big deal.
If the story is about a person who must get a serial killer roast beef or they will kill again, and they find out that three of the four stores in their area are out, then “that had roast beef” specifies which of the four stores you went to. It’s essential information, because if you delete it, the reader will think: which store? Are they wasting time picking up some quinoa pasta at the Whole Foods when they need to be getting to the roast beef store?
As you can see, the meaning doesn’t change all that much if you use the wrong one here, but there’s still a correct choice between the two words. If you play fast and loose with this distinction, puppies aren’t going to start hiding their faces, so the stakes aren’t as high.
And there you have it. Some comparisons that actually make sense. I hope that helped.