Whatever “that” means. (Susan Walsh/ASSOCIATED PRESS)

That is the question.

Some of the most bitter battles of our time have been waged over grammar. The Hatfields and McCoys were chums compared to the people who think semicolons are always a sign of pretension and the people who sprinkle semicolons liberally over all their writing, like salt. At perfectly convivial gatherings, just let someone introduce the question of how many spaces belong after a period, and the guests start lunging at each other with knives.

To split the infinitive? Or to not split?

To be? Or not “to be,” since an active verb is always better?

Which or that? Oxford commas or regular commas? A preposition at the end of a sentence? That’s a thing up with which I will not put!

“I am the Emperor of Rome,” said Emperor Sigismund in 1414 to a querulous prelate, “and am above grammar.”

But who is above grammar?

Not even the president, it turns out.

The problem with President Obama’s much-ballyhooed quote “You didn’t build that” comes down to this same question. Grammar, or philosophy?

In context, the quote runs: “If you were successful, somebody along the line gave you some help. There was a great teacher somewhere in your life. Somebody helped to create this unbelievable American system that we have that allowed you to thrive. Somebody invested in roads and bridges. If you’ve got a business, you didn’t build that. Somebody else made that happen.”

Leaving aside the question of who this vague Somebody is who keeps investing in everything (call me, Somebody! I have a venture for you!), what exactly is “that”?

“Not business!” the defensive multitudes shout. “He was talking about the roads and bridges!”

Shouldn’t it be “those,” then?

This is a classic case of unclear antecedent. If he was talking about ”this unbelievable American system,” that’s two sentences ago, and we have forgotten all about it!

This is the sort of thing that causes one’s eighth-grade grammar teacher to leap up and down tearing out large fistfuls of her hair.

Most logical indications point to the word “business” — in the same sentence — as the antecedent. But that would be far too radical.

No, better avouch bad grammar than disdain business. Grammar doesn’t matter. “Give me Liberty or give me that!” “The only thing we have to fear is that, itself.”

Which? What? Whose? When? Where?

Who knows? We’ll fix it in post!

Either “You didn’t build that” is a philosophical statement that entrepreneurs did not build their businesses on their own, and it’s deserved every inch of coverage it’s received — or it’s a deplorable failure of grammar. Most people would be more upset by the former. But the latter is, in its own way, just as frustrating.

Grammar is a form of courtesy to your reader or listener. It ensures that when you say “this” you mean the same “this” that everyone thinks you mean.

That depends on what the meaning of the word “is” is?

Start redefining “is” and repositioning “that,” and you slide down the fire pole of national esteem. “I didn’t mean ‘business’ when I said ‘that,’ ” you say. “I meant ‘Grand Tetons National Park,’ which I mentioned six pages earlier! Duh!”

What is that? Who are they? What are these? Where am I? Who are you? What are we talking about? If ours were an inflected language, this might be simpler. But, alas, it isn’t.

And I’m certain that within moments of posting this, I will notice several grammatical errors. It’s Murphy’s Law: Write anything criticizing someone’s writing or grammar, and inevitably you will have erred yourself. ]

They say that literature exists so that where one man has lived finely, thousands may afterward live finely. Grammar exists so that where one man knows what he means, thousands may afterward also know what he meant. There is a flip side, of course.

Speak with bad enough grammar, and no one will ever have any idea what you are trying to say. Perhaps this is the future of our national discourse. People with good grammar are so easy to pin down onto actual positions — always a liability! Eschew grammar! Forget proper structure! Do what Jimmy Durante did. Don’t just split your infinitives; chop them up into little pieces! For politicians, this might be a safe bet. Throw enough unclear antecedents in there, and you could be saying anything at all.