I said I would not have much to say about the mechanics of copyediting – there will be some — but I’ll start off with this exception, because when you tell people you are a copyeditor, it tends to come up early. “So you know the difference between that and which?” “In fact, I do,” I say. That leaves them in awe. I didn’t know the difference when I started out, and I don’t remember when the difference became clear to me, but Lord knows I do know now, and it is now.
I was assigned a philosophy monograph a couple of years ago, a long and impressive one, that swept up basically all of world history into a single elaborate skein of deep rumination. He explained why everything that has ever happened actually happened, and he condensed millennia of world history into a blaze of erudition that lit up my monitor. Seven hundred pages of that, which, if you’re getting paid by the page (which I was, more or less), is bloody wonderful. I was enthralled. But I wrote this note to the ME before I got too deep into the task:
“Some strange things I AM adjusting: he’s got an unwieldy dread of ‘that,’ and bends over backwards to use it less than he should. Strange, like I said. ‘Which’, ‘i.e.,’ or no word at all are his preferences when ‘“’that’ would make more sense.”
In other words, an author that articulate and erudite was unsure of the difference, and he was writing around it, obviously. I was asking the ME for the go-ahead to apply that/which correctly to seven hundred mscript pages. His answer was “I don’t always know the difference either. Are you sure you do?” “Absolutely sure.” “Go ahead,” he told me, and I did. It was like picking birdshot out of a basket of quail, for weeks on end. It completely changed the tone of the mscript. Sometimes, at this desk, I have told myself, “I’ve got the nerve to do this to a manuscript.” It usually has to do with recasting documentation, but within the text itself? That is a much more fraught exercise. I sent the finished mscript to the author for review, and yes he did notice, and he thanked me quite graciously. But I had taken a chance that he would accept the shift, and it could have gone some other way.
I also remember starting out four decades ago and struggling to understand the difference. Checking one dictionary after the next, looking for style guides in the library to explain it to me (there was no internet back then – it was a library visit on nothing). They all had explanations of varying lengths, all of which explained it differently and none of which seemed to agree (peripheral/non-peripheral, essential/non-essential … gad …). But at some point, I don’t remember exactly when, though it would have been years later, something went “click.”
I won’t try to explain the rule here. That would only be adding to the noise, and the question has already generated enough of that. But I will offer this principle to remember. “Greyhounds, which have four legs, are fast runners.” “Greyhounds that have three legs are also fast runners.” Ninety-eight percent of what you have to know about that/which is collapsed into those two sentences. If you stare at those two long enough, the difference will come to you.
ADDENDUM: Copy editing lends itself to sudden curves and occasional blind alleys. Here’s one: not all gray hounds are greyhounds. Webster spells it gray, so, why does it also have greyhound? Webster doesn’t tell you the etymology of words, but Oxford does, and it tells you that the grey in greyhound is from an Old Norse term meaning “bitch.” That’s why Webster has it as greyhound.
Etymology can be useful, and even fun. In situ is Latin for “in position.” So I always apply where to the word “situation”: “In situations where …” Never when. I don’t know what other CEs do, or whether it’s necessary, or even correct, but it’s what I always do, and no one has complained.