This essay was first published on Dark Gray Matters in October 2021. It is part of the science style guide series.


There are famous words from Gary Provost that go like this. Pay attention to the rhythm:

This sentence has five words. Here are five more words. Five-word sentences are fine. But several together become monotonous. Listen to what is happening. The writing is getting boring. The sound of it drones. It’s like a stuck record. The ear demands some variety.

Now listen. I vary the sentence length, and I create music. Music. The writing sings. It has a pleasant rhythm, a lilt, a harmony. I use short sentences. And I use sentences of medium length. And sometimes when I am certain the reader is rested, I will engage him with a sentence of considerable length, a sentence that burns with energy and builds with all the impetus of a crescendo, the roll of the drums, the crash of the cymbals—sounds that say listen to this, it is important.

So write with a combination of short, medium, and long sentences. Create a sound that pleases the reader’s ear. Don’t just write words. Write music.

This is legendary advice for writing sentences. It is delightfully illustrative; we grasp it immediately. And it is correct: diversity in sentence length is a necessity of good writing, just like it is for musical notes.

I claim that the same is true of paragraph length.

Science papers usually feature many long paragraphs. Often, all or almost all paragraphs in a paper are long.

Put negatively, we might call them Walls of Text. This is a good metaphor because Walls of Text, just like regular walls, serve as obstacles. They make information less accessible. How often have you looked at a Wall of Text and simply decided it wasn’t worth the effort?

Walls of Text are bad because:

  1. They make it more difficult for readers to take breaks.
  2. They provide no hints about the structure of the underlying ideas.

We’ll examine both in more detail below. But first I want to tie my ideas about paragraphs with my two major writing style principles.

Minimum Reading Friction: The point of having paragraphs at all, as opposed to perfectly continuous text with no line breaks, is to provide some help for readers. If you don’t do that, you’re essentially telling your readers that they’re on their own. This is the opposite of what we want — the effort should be made once, by the writer, so that the many readers don’t have to.

Low-Hanging Fruit: Cutting up paragraphs is a relatively easy task. If the sentences are structured well already, it’s just a matter of finding the “joints” in the written text where it makes sense to add a line break. If the ideas are structured in a confusing manner, then it’s more work, but there’s also greater room for improvement.

In the interest of not making this post too long, I won’t include a full-fledged example, but this past post in which I rewrote a paragraph (into several ones) is a good illustration.

1. Rewarding the reader with breaks

Humans aren’t computers. We can’t work continuously without resting. Reading science papers text is work, so we’re always on the lookout for opportunities to take breaks — sometimes microbreaks on the order of a few seconds, sometimes longer breaks like a full day.

Paragraphs, like chapters, sections, and sentences, serve the purpose of telling readers, “hey, good job, you read a thing, now you can take a break if you want.” It’s rewarding. It indicates that it’s safe(r) to take a break after a paragraph because it’ll be less work to find a reentry point later, and because you expect the next paragraph to be about a different idea.

I don’t know if it’s a coincidence that the word break is used for both concepts, but if so, it’s a fortuitous one.

Walls of Text are often bad because when they loom ahead, you brace yourself. You wonder if you’ll have the energy and time to read it all. If not, maybe you quit reading (and it’s anybody’s guess whether you’ll come back to it later). If yes, then you come out at the other end with less energy and time, and good luck if the next paragraph is also a Wall of Text. And that’s assuming you do reach the end. It’s quite likely that you quit halfway — because you had to stop to think about something you read, or you needed to look up a word, or you clicked on a link, or some random distraction outside the text grabbed your attention.

At the most extreme, you could imagine an entire book that consists of a single paragraph, with no chapters or line breaks at all.1 This is really lazy on the part of the writer — the reader has to do all the work!

Now, that’s not to say long paragraphs are always wrong. Sometimes it really does make sense to package a lot of ideas together in a single Wall of Text. Also, long paragraphs can be easy to read if the sentences are good and logically connected. But this also means that if you do choose to write a Wall of Text, then you should be extra careful with how you structure the writing inside it.

2. Providing structure

Speaking of structure: line breaks are one of the most useful tools to communicate structure to readers.

We expect paragraphs to contain a single idea. You may have learned in school that a paragraph should have a “topic sentence” with additional sentences to provide “supporting detail.” This is somewhat too rigid, but the principle is sound.

The worst kinds of Walls of Texts are those that have multiple competing ideas inside them. Find where the boundaries are, and cut them up! The ideas don’t even have to be very different. Suppose you have a transition word like “Similarly” or “Alternatively” in the middle of a paragraph. The next sentence if probably closely related to the previous one, but the transition word does indicate a shift, so it’s a nice spot for adding a line break.

Of course, sometimes you really have a single idea with lots of supporting detail that it makes to sense to break up. This is why Walls of Text are sometimes useful.

In fact, as the Gary Provost quote at the top illustrates for sentences, diversity in paragraph length is a good thing.

Having only very short paragraphs is bad.

Think of low-quality newspaper pieces where there’s a line break after each sentence.

It’s jarring.

This is almost as bad as Walls of Text, from the point of view of structure.

Okay, that was annoying, right? The reason is that sentences already provide structure. So using only single-sentence paragraphs amounts to not using line breaks as an extra channel for reader guidance.

Strive to have a mix of short, medium, and long paragraphs. Heterogeneity is good. It carries more information.

Recommendations

  • If you’re ever debating whether or not to end the paragraph and add a line break, err on the side of “yes”.
    • Verbatim from Slate Star Codex’s Nonfiction Writing Advice, an excellent essay whose section 1 heavily inspired this post.
  • Balance your piece between short, medium, and long paragraphs.
  • Cut up existing Walls of Text by finding the boundaries between different ideas.
  • This advice generalizes to section breaks:
    • Err on the side of more shorter sections rather than few long ones.
    • Split sections that are long and contain many distinct ideas.