Slate has a nice piece up on why it’s totally, completely wrong to double-space after a period. I get this all the time in documents I edit—I usually just do a quick find/replace to eliminate all double-spaces from the document at the very start. I remain continually surprised at how many (even those who learned to type in the last decade) commit this typography foul, a holdover from the days of typewriters with monospaced fonts. Please, for the sake of humanity, stop doing this, people—at least eliminate the spaces via find/replace after you type the document! (FULL DISCLOSURE: I was taught to put two spaces after a period when I learned to type also; it was a real pain to unlearn it a few years back.)
Perhaps more interesting is how several teachers cited in the article explained that they teach/require their students to put two spaces after a period even though they know it’s wrong. Why? Because they learned it that way themselves. Remarkable. So not only are they showing themselves to be unwilling learners, they are willing to teach the wrong thing just because it’s more comfortable for them. That pretty nearly sums up the definition of an unwise person and bad teacher; unfortunately, it’s how many teachers (and parents) choose to educate the next generation.
Yes, I know it’s just typography, but the larger point is worth making. The capacity and willingness to receive correction is a first step to becoming competent and wise. Or, put differently, the first step in being correct is actively seeking and accepting correction. If we stubbornly stick to what’s comfortable or “the way we were [first] taught,” we’ll be on the wrong side of a lot of things over the course of our lives—and worse, we’ll pull others along with us. As the proverbs say: הוֹכַח לְחָכָם וְיֶאֱהָבֶךָּ “correct a wise man and he will love you” and אֹהֵב מוּסָר אֹהֵב דָּעַת וְשֹׂנֵא תוֹכַחַת בָּעַר “Whoever loves correction loves knowledge, but the one who hates rebuke is stupid.”
We should all make this a rule of life: rather than eschewing correction and resting comfortably in what (we think) we already know, we should actively and tirelessly seek correction so that we can truly know—and only then can we, as wise people, instruct others. And by no means should we ever teach the next generation to do what we know to be wrong, simply because it’s how we first learned it.
UPDATE: This subject has apparently hit a nerve across the web, including some pretty witty responses like the following: “everyone has a right to their [sic.] beliefs,” which (despite the number disagreement in its subject line) nicely critiques the Slate article for sloppy argumentation. (Yes, it would have been better had he mentioned more empirical arguments like the fact that double-spacing wastes precious space in print, etc.)