English ain't algebra
You can hear, in the dispute about singular they and other issues of grammar and usage, a complaint that a usage objected to is not logical. For example, the objection to the double negative is that two negatives make a positive. In mathematics, yes. But step up, you two-negatives-make-a positive people. I want to hear you say that the first time you heard Jagger sing “I can't get no satisfaction,” you understood him to mean “I’m satisfied.”
At the Geoffrey Pullum post on singular they at Lingua Franca that I wrote about yesterday, a copy editor writing as odarp thought he could put Professor Pullum on the spot, asking, “If ‘they’ can be singular, why does it always take a plural verb?” To this, jffoster replied, “The pronoun you can be and often is singular. But it always takes, in all standard and most nonstandard dialects of English, a plural verb are, were, .... Why doesn't that bother you?”
One of the people troubled by the singular they discussion is Andrea Behr, who commented on my post yesterday: “What confuses me is how do you know what's still a rule and what isn't? Why, for instance, is subject-verb agreement still a rule and pronoun-antecedent agreement isn't? If it's just a matter of how people actually use the language, why is there still a rule about when to use 'whom'? (if there is) Nobody uses it in speech, and in my experience, few writers use it either.”
The fact is that subject-verb agreement and pronoun-antecedent agreement are still rules in English, and there are still rules for using whom for those who use it, which is why those who still use it often get it wrong. It’s just that the rules are not necessarily simple (and—how often must I say this?—some things that people think are rules are not).
My fellow copy editors are keen for certainty, for rules, for consistency. Some of them, particularly the AP Stylebook fetishists, would like everything to be a 1 or a 0, right or wrong. And I myself, I blush to confess, have issued rulings to writers without considering context or, for that matter, whether the house style rule made any sense in the first place.
I understand that need for certainties to cling to in this earthly and transitory life, and I understand that that need leads some people to go overboard. And if the rules you were mistakenly taught in childhood are the flotsam that keeps you above water, I wouldn’t care to see you sink.
But if you are making a living by the craft, if you are a writer or editor, it is incumbent on you to get beyond mere rule-following and make judgments. English is not some Platonic ideal that exists apart from the people who use it; it is what the people who have used it and continue to use it make of it. That is why you should pay attention to the historical and contemporary evidence that linguists like Professor Pullum produce. That is why you need to be attuned to how the language is being used today, broadly. That is why you need to periodically examine your own assumptions. Only then are you going to be able to make appropriate judgments taking into account writer, publication, audience, and occasion.