In my Effective Writing training course, I pose a provocative question. After a full stop, should there be one space or two?
It's provocative because there's no correct answer. Everyone will have been taught a particular way is correct, and many people get quite angry that not everyone else agrees.
I then present this XKCD cartoon as a talking point.
The intent is to illustrate that language rules - grammar, spelling, punctuation - are defined by consensus. What's correct English now is what people are actually writing and speaking now. That might be different to the consensus a hundred years ago, and, given today's level of connectivity, will likely be different again in a much shorter time period. But sometimes, we just don't agree on the rules, and that's where a style guide can be helpful - to help us agree to disagree, defer to an authoritative source, and move on.
Finally, I ask participants in the course to guess whether Microsoft Word's grammar check treats one space or two as correct. It's actually a trick question: Word can be configured to treat either, or neither, as being incorrect.
There is some objective history behind the question, and I have a personal opinion on what this means for the correct answer to the question. First, for most of the twentieth century, letters were typewritten and therefore monospaced, or fixed-width. That is to say, the typewriter carriage moved forwards a fixed amount when a letter was typed, no matter how wide the letter - i or l, m or w.
Text is easier to read if the space between sentences is clear and obvious. This means that a double-space after a full stop actually did make typewritten documents easier to read. I don't believe any of this is contentious. What is perhaps contentious is whether the same rule should still apply now that we all have word processors that can deal with letters of different widths.
Indeed, the width of the letter m is used as an actual unit of measurement in typesetting - called the em (as in the "em-dash", as opposed to an "en-dash").
My personal view is that it's bad form to change the content of data to make the formatting work properly. For that reason, I am content to say that one space is correct, and we should rely on our word processor (or web browser or whatever) to lay the text out neatly. Plus, it's very slightly less effort.
In fact, in HTML, multiple consecutive whitespaces condense down to a single space anyway. Type two spaces after a sentence, or anywhere else, and your browser will helpfully get rid of the second one.
All this is a rather long preamble to introduce a momentous piece of news: the world has decided - or at least, Microsoft has - that there is a definitive correct answer to this vexing question. And that answer is, as I would have hoped, that single spacing is correct. The linked article talks about the dubious research on the topic as well.
I don't think that this will settle the debate at all. Indeed, there will likely be some people who hold out against this decision precisely because it's Microsoft that's tried to settle it. But Microsoft's action tends to imply that the consensus has definitively shifted to the one-space view, and also ensures that most people will be encouraged to single-space in the future.
A version of this article was originally published on my company internal blog.