Barton Swaim is opinions editor for the Weekly Standard.

President Obama delivers his 2015 State of the Union address before Congress. (Astrid Riecken/European Pressphoto Agency)

Donald Trump is two weeks away from the presidency, and the world of political journalism rumbles with the question of whether journalists should call him a “liar.” I agree with the Wall Street Journal’s Gerard Baker, whose comments on “Meet the Press” last week started the brawl, that the word “lie” and its cognates should be applied to public officials with extreme caution. Inasmuch as it is a reporter’s job to give readers only verifiable truth, and the word lie implies the often unknowable component of motive, it’s best left out of the discussion — even when it seems all but certain that the public official, in this case Trump, knew what he was saying was untrue when he said it.

Baker’s concern is mainly with the propriety or impropriety of journalists, particularly reporters, calling Trump a liar. There’s a closely related point to be made, too, and it’s this: Once you call someone a liar, even if he is one, there’s no end to the number of people you’ll be calling liars. That’s especially true in politics, a field in which — I think we can say in the abstract — a lot of people lie.

There are, however, a few places in the world where most uses of the words “lie” and “liar” are forbidden — namely parliamentary bodies. In the U.S. Congress, the House of Commons and House of Lords in London, the Parliament of Canada, and many other diets and congresses and parliaments, the attribution of deliberate dishonesty falls under the category of “unparliamentary language.” It’s a broad category; in the United Kingdom’s Parliament, for example, a member may not call another member a coward or a hooligan or a “git” (whatever a “git” is — I’m afraid to Google it).

All these bodies proscribe members calling other members liars or accusing them of intentionally misleading. Debating rule number XIX.2 in the U.S. Senate, for instance, reads:

No Senator in debate shall, directly or indirectly, by any form of words impute to another Senator or to other Senators any conduct or motive unworthy or unbecoming a Senator.

The key word is “motive.” To call someone a liar is not to say he spoke an untruth. It’s to say he did it willingly.

A shouting match erupted at an election postmortem session, where aides from both campaigns met to discuss the election. The Washington Post's Margaret Sullivan and Callum Borchers talk about what happened. (The Washington Post)

The reason for the rule is not that members of parliamentary bodies don’t lie. Everyone knows they do. They know they do. The reason for the rule is that once you allow the word “lie” or “liar” to be used by one member against another, the debate’s over and the whole thing descends into name-calling. You can’t have a reasoned discussion with someone who questions your good faith.

Remember Rep. Joe Wilson (R-S.C.)? Not ordinarily an animated debater, he surprised even himself, I suspect, when he shouted “You lie!” at President Obama during a 2009 speech Obama gave before Congress. The House later rebuked Wilson by a mostly party-line vote of 240 to 179. The president may have been lying; he may have been merely misstating the truth; or Wilson may have been wrong. None of that matters. The point is that Wilson did what you can’t do in a body that relies on reasoned discussion, and he should have been censured.

Of course, journalists and Trump aren’t peers on a parliamentary body, and the word “lie” has become synonymous in our political discourse with “a statement I don’t like.” Everything’s a “lie” these days. A politician or a commentator can hardly utter a semi-controversial remark without someone — not just a Facebook troll but a respectable political adversary, speaking on cable TV — calling him a liar or suggesting that he’s deliberately misleading the masses.

Maybe Trump’s a liar. I’m not prepared to say he’s not a liar. But that word can get away from you if you’re not careful.