Forget politics.  Forget philosophy.  If you want to start an argument in a room full of wordsmiths, raise the question of whether one space or two should follow a period.

Consider, for instance, this blast of the trumpet against the dreaded two-spacers, published back in 2011:

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

And yet people who use two spaces are everywhere, their ugly error crossing every social boundary of class, education, and taste.

In part the divide is a cultural one, with typographers (who work with proportional fonts and are concerned with beauty and readability from the consumer’s end) on one side, and writers and editors (who have traditionally worked with monospaced fonts and are concerned with making the text clear and easy to work with on the production end) on the other side.

There’s also a generational component in the spacing war.  Older writers, who learned to type on manual or electric typewriters that produced monospaced output, were trained to space twice after a period, for clarity’s sake.  Writers who came later to the trade, on the other hand, learned keyboarding on personal computers with access to proportional fonts, and were taught the typographer’s one-space principle.

Who’s right?  It doesn’t matter.  The glory of word processing is that you can write your book whichever way you were taught, without having to worry about retraining your spacebar thumb.  Then you can go to your publisher’s guidelines, and see if they have a stated preference.  If they do, then use the mighty power of global search and replace (if your word processing program doesn’t already come with a built-in “convert two spaces to one space/one space to two spaces” option) to make your text conform to the desired standard.

If the publisher doesn’t have a preference, then go with what you’ve got.  Or, if you’re still uncertain:  If you’re working in a monospaced font (which is to say, in Courier New – there are other monospaced fonts out there, but when an editor thinks “monospace” they think “Courier New”), then space twice after the period.  If you’re working in a proportional font (which is to say, Times New Roman, because the last thing an editor wants is to read a manuscript where the author has gotten cute with the fontwork), then space once after the period.

And don’t stress out about it.