As style disputes go, very few produce more polarization than the proper use of the serial comma and the number of spaces that should follow a period.
Proponents and opponents of the serial comma (also known as the Oxford comma) will practically come to blows to defend their side.
And whether one or two spaces should follow a period is an ever-raging online clash.
In this post, I'd like to present a unified style theory, which provides a consistent justification for the correct opinion on both matters:
Prefer the option where muscle memory has the least chance of negative effects.
That's it. That's the whole thing. But in case you're curious about why this theory should be adopted, and what its practical consequences are, read on!
In the case of both serial commas and spacing after a period, there is an interesting matrix of potential outcomes for each style choice.
Let's examine serial commas first.
In the majority of cases, whether a serial comma is used does not affect the meaning of the sentence. In these cases, the worst outcome of using it is unnecessary effort.
But in a minority of cases, whether a serial comma is used can absolutely affect the meaning, as illustrated by this old joke about a book dedication that lacks a necessary serial comma:
To my parents, Ayn Rand and God.
In these cases, the worst outcome of omitting a serial comma is a potentially drastic change in meaning.
Most style guides, such as the hallowed Associated Press style book, which I followed during my years as a copy editor, note that in cases where a serial comma is necessary to preserve meaning, it should be added. But that requires a person to always be attentive to the exceptions to the rule, which requires more mental effort than just using the serial comma all the time.
Similar to the serial comma, in the majority of cases, using two spaces after a period doesn't matter, because nearly all text editors and design tools, at least those designed for prose writing, will strip away the second space when the writing is displayed. For instance, I'm writing this paragraph using two spaces after each sentence, but HTML, when rendered, will use only a single space between sentences.
But in a minority of cases, using two spaces instead of one can indeed improve readability. Specifically, when using monospaced fonts, such as the font in this paragraph, having two spaces after each sentence is beneficial. These fonts are widely spaced, so the extra space between sentences more clearly divides them. Monospaced fonts are used in software development, in scripts for film or stage, in many online forms, and for a variety of other purposes, so most people are going to write using these fonts at some point. And even if you aren't displaying your writing using a monospaced font, that doesn't mean your text couldn't be copied into a monospaced format by someone else, perhaps for accessibility reasons, and in those cases, you will have already made the right formatting choice.
Having the habit and muscle memory to use two spaces after a period means you don't even need to think about it. Whereas if you're normally a "one space after the period" type of person, now you have to pay special attention to every spot where you need to adjust the habit whenever you use monospaced fonts.
If, in both cases, there is a more common scenario where your style choice makes basically no difference, but another, less common scenario where your style choice does matter, I contend that you should take the lazy person's route and adopt, as a general preference, the option that builds the type of muscle memory that has the least likelihood of negative effects.
In the case of serial commas, that means using them consistently, rather than only in the cases where their absence would affect the meaning of the sentence.
In the case of spaces after a sentence, that means using two spaces consistently, rather than only in the cases where they clearly provide a readability advantage.
Trust me, you won't notice the extra keystrokes once you get used to it, and you will save yourself plenty of time later on by not having to ever think about whether the extra characters are essential or not.
Shaun Gallagher is the author of three popular science books and one silly statistics book:
He's also a software engineering manager and lives in northern Delaware with his wife and children.
Visit his portfolio site for more about his books and his programming projects.
The views expressed on this blog are his own and do not necessarily represent the views of his publishers or employer.
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