A FRIEND of Johnson’s recently posted on Facebook a January 2011 article by Farhad Manjoo on Slate that began

Can I let you in on a secret? Typing two spaces after a period is totally, completely, utterly, and inarguably wrong.

That the article is still being passed around, and has been shared on Facebook over 165,000 times, reveals a surprising passion on this issue. But the comments on my friend’s Facebook posting also reveal a slightly depressing willingness of people to be cowed by anyone who stands on an internet soapbox and declares inarguable rules. “Now you’ve set me straight,” one commenter wrote. Another was surprised at not having heard about the new rule earlier; her mother was, after all, “a grammarian at heart” and had taught her to be on the lookout for such things.

Well, Johnson has a secret, too: pronouncing a diktat like “never use two spaces after a full stop” is not totally, completely, utterly and inarguably wrong—but it is mostly wrong.

Many people have the idea that absolutely everything to do with language is governed by strict rules. A corollary is that these rules must only leave one option. If one space is correct, then two spaces must be totally, completely, utterly and inarguably wrong.

The history of the dispute is simple enough: typesetters have been using one space after a full stop for most of a century. But people who learned to type on mechanical typewriters with monospaced fonts were taught to use two spaces, because monospaced fonts (in which all letters have the same width) leave white space on either side of skinny letters like i and l. So two spaces at the end of sentences was meant to convey meaningful (rather than meaningless) space on the page. Johnson learned to touch-type around 1990, when word processors had nearly completed their replacement of typewriters. But the teacher had learned to type well before that, leaving your columnist with a two-space habit that persists to this day.

But can the vast number of professional writers and editors who learned the two-space habit be “inarguably wrong”? Is this really bad grammar? No, and no. Grammar has nothing to do with aesthetic issues like one space or two. Grammar has to do with how words hang together to make meaningful sentences accepted as correct by native speakers. Grammar has inarguable rules (the past tense of “I am” is “I was”). But it also has disputed ones. Some people think that “which” can be used interchangeably to open “restrictive” relative clauses, like “The rules which I learned in school are inviolable.” Others disagree.

But we are not remotely near the territory of grammar when we talk about the two-space rule. We’re barely in the territory of rules at all. The relevant concept here is not grammar but style. The Economist, as it happens, follows the prevailing practice and puts only one space after full stops. An automatic macro will, for example, strip out the second space after a full stop for any text entered into our online content-management system (ie, the one we use for blogs and online columns like this one). If you do see any double-spaces after a full stop, this is probably the result of text being pasted from Microsoft Word, and the oversight of an editor.

But the one-space “rule” is not the kind of thing that separates good writers from bad ones. It is rather for simple aesthetic consistency. In this, it belongs in a category of style choices at The Economist that includes hyphenating e-mail, stripping Yahoo and Yum Brands of the exclamation points they would have us use in their names and leaving internet lower-case. Some of our rules are mainstream (e-mail is more common than email). Some are unusual (we do not capitalise cold war or second world war). But nobody could sensibly insist we were “wrong” on these. Style choices, by definition, cannot be wrong.

Some people seem to think love for language means memorising the longest possible list of grammar rules and style shibboleths. This is too often coupled with smug self-congratulation. But a real understanding of language acknowledges which rules are truly ironclad, which ones are in dispute and which ones are mere style choices.

There is one double-space after a full stop in this column. For fun, see how long it takes you to find it. If you noticed it already, and it distracted you from the rest of the piece, Johnson humbly suggests you might be focusing a little too much on the wrong things.

Do you have a question or a column idea for Johnson? Write to johnson@economist.com.