It's all about the spacing

Are you still one of those people who puts two spaces between sentences when you type? Well, stop doing it. Because it's wrong.

Every modern typographer agrees on the one-space rule. It's one of the canonical rules of the profession, in the same way that waiters know that the salad fork goes to the left of the dinner fork and fashion designers know to put men's shirt buttons on the right and women's on the left. 

Every major style guide—including the Modern Language Association Style Manual and the Chicago Manual of Style—prescribes a single space after a period. (The Publications Manual of the American Psychological Association, used widely in the social sciences, allows for two spaces in draft manuscripts but recommends one space in published work.)

Most ordinary people would know the one-space rule, too, if it weren't for a quirk of history. In the middle of the last century, a now-outmoded technology—the manual typewriter—invaded the American workplace. To accommodate that machine's shortcomings, everyone began to type wrong. And even though we no longer use typewriters, we all still type like we do. (Also see the persistence of the dreaded Caps Lock key.)

The problem with typewriters was that they used monospaced type—that is, every character occupied an equal amount of horizontal space. This bucked a long tradition of proportional typesetting, in which skinny characters (like I or 1) were given less space than fat ones (like W or M).

Monospaced type gives you text that looks "loose" and uneven; there's a lot of white space between characters and words, so it's more difficult to spot the spaces between sentences immediately. Hence the adoption of the two-space rule—on a typewriter, an extra space after a sentence makes text easier to read. Here's the thing, though: Monospaced fonts went out in the 1970s.

First electric typewriters and then computers began to offer people ways to create text using proportional fonts. Today nearly every font on your PC is proportional. (Courier is the one major exception.) Because we've all switched to modern fonts, adding two spaces after a period no longer enhances readability, typographers say. It diminishes it.

The fact that Courier is monospaced makes it useful for creating tables, which is why folks like Kuff use it in their blogs, but I think that Courier is an otherwise aesthetically unappealing font. When I read or type something, I want it to look nice. And putting two spaces after a period just.  Looks.  Really.  Ugly.

But I actually think aesthetics are the best argument in favor of one space over two. One space is simpler, cleaner, and more visually pleasing (it also requires less work, which isn't nothing). A page of text with two spaces between every sentence looks riddled with holes; a page of text with an ordinary space looks just as it should.

Is this arbitrary? Sure it is. But so are a lot of our conventions for writing. It's arbitrary that we write shop instead of shoppe, or phone instead of fone, or that we use ! to emphasize a sentence rather than %. We adopted these standards because practitioners of publishing—writers, editors, typographers, and others—settled on them after decades of experience. Among their rules was that we should use one space after a period instead of two—so that's how we should do it.

Perhaps because I never took a formal typewriting class in school, I never learned that there was such as thing as a "two-space rule." All of my word-processed assignments in high school, undergrad and grad school were written with a single space between periods, and none of my teachers or professors ever told me otherwise. It wasn't until I got my first job after grad school, and the director of the department I worked in groused to me about not putting two spaces between sentences in my reports, that I even discovered that it was an issue. Needless to say, I was surprised and loathe to change the way I typed just to appease a boss demanding a convention I had never previously heard of that turned out to be wrong anyway.

The truth is, it's not a big deal to me if somebody likes to put two spaces after a period. Maybe that's how they were taught, or maybe for some bizarre reason they think it looks better. That's fine; just don't expect me to do it. According to every major style manual, as well as my own aesthetic sensibilities, typing a single space after a period is correct.

That guy's not my boss anymore, of course. Nor, from what I hear, anybody else's boss anymore, either. And I haven't had this issue with any employer or client I've worked for since.