Most novels are written in "literary past," that is, they are in grammatical past tense but are presented as if the scene is happening right in front of us. It's so conventional that we seldom have to think of it or consciously choose past tense.
But I use the term "that is" far too often in real life, and it creeps into my writing, and so do other present-tense terms, especially in deeper POV, when presumably this is being narrated by the POV character.
Here's an example:
She pushed the rewind button-- well, it had some other name, but that is what it did, rewind the video.
That's pretty easy to change to "that was", but what about when you use "that is" in that explanatory way, as "for example" or "what I really mean is" or "let me see if I can word that better this time" (as I did in the first sentence of this post). And whenever I do that, I think I should word it better the first time, but you know, sometimes in deep POV, I might want to show that whatever this is is difficult to explain, or maybe hint that the narrator has some problem being open about this.
The world didn't work that way, that is, he was wrong again.
Groan. It's late and I can't find a good example. But anyway, when "that is" is used in its conventional sense (i.e., I guess), and you're writing in literary past, do you change it to "that was"? Sounds very weird.
Another -- you know, I am really reductive tonight... actually focusing on one word-- is. -- another example of present-in-past is when you're describing something that exists in the real world, like:
He found himself on Adams Street, staring up at the Sears Tower. That is 110 stories of black glass...
Well, it's true. The Sears Tower IS whatever it is, because it's real. Or would you say, That was 110 stories.....
I notice some writers, when they're talking about something real, often use present tense.
He took her to Emeril's that night, that is, a seriously expensive tourist destination--
Alpha Centauri is the nearest star to the solar system, and that's where Tom was headed in his space cruiser....
The Hope Diamond has always been a treasure coveted by felons---
Well. I know, when I edit, I usually change these to past tense. Why call attention to something being "real" (note the quote marks around "real"-- I mean, really, what is real, huh?) and thus implying that all in past tense is, you know, fiction?
But it's sort of silly for us to pretend that we made up the Sears Tower or Alpha Centauri, and isn't that what we're doing when we put mentions of them in past tense?
There are things that are... uh, kind of universal, generalizations we make. Let's say the heroine of your new story is, mirabile dictu, an editor! (Let's pass on the issue of whether a novel has to be interesting. :) And you have a scene where she's reading a submission done entirely in present tense (I actually am more adaptable in my own reading than poor 20th Century Emily... I don't have much trouble with present tense stories):
Emily was a paragraph into the first page before she realized why she was so disquieted. The opening scene was in present tense. Most novels are written in "literary past," that is, they are in grammatical past tense but are presented as if the scene is happening right now. And this book, well-- she flipped to page 237, and it was still present tense.
She shivered. There was something wrong with the night. She closed the manuscript and went to the window. Were there demons out there? Present-tense demons?
She felt very alone.
There is a generalization that is true, and not just in the World of the Book, but in our world too. So do you show that it is True with a capital T by using present, or what?
Okay, so I'm obviously searching for items to prove how Very Difficult it is to edit. :) But really, have you ever come across this issue as you write? I tell you, every time I edit something that has this issue, it presents an existential dilemma.
Alicia who obviously needs something more important to worry about