Here is a simple way to tell whether a politician is lying. A politician is lying when a politician states an untruth from which the politician stands to benefit.
This is not a hard idea to understand, but let's run it through a quick hypothetical. Here is a politician. He is talking! The words coming out of his mouth refer to people and events and circumstances, aspects of the external world that do not exist solely within the politician's imagination. Do his words depict this external world accurately? If they depict it inaccurately, does their inaccuracy in some way advance the politician's agenda? A politician who misrepresents the external world in a way that serves his interests is lying.
The president of the United States, Donald Trump, is a liar. He habitually makes statements that are not true, and the effect of those statements, if one makes the mistake of believing them, is to cause him to look better and his opponents to look worse. When he says, for instance, that he lost the popular vote only because millions of illegal immigrants voted for Hillary Clinton, he is both (a) contradicting verifiable facts, and (b) doing so in a way that makes him look more important than he really is, more prophetic than he really is (since a number of his other lies have revolved around allegations of voter fraud and election-rigging), and more unjustly victimized than he has ever been at any moment in his life.
If he were being inaccurate without also being self-serving — if, for instance, he said that millions of illegal immigrants had voted for him, a statement that is also untrue but that would serve to weaken his position instead of strengthen it — it might be reasonable to conclude that he was simply making a mistake. If he were being self-serving but not inaccurate — boasting about the size of his plane, say, which is in fact pretty massive — it might be reasonable to conclude that he was simply an arrogant prick. When he is inaccurate and self-serving, however, there is no reasonable conclusion except that he is lying.
The job of the news media, broadly speaking, is to report what happens. When the president lies, the job of the news media is to say that the president is lying. Faced with Donald Trump's lies, however, our news media has gone spiraling off into an abstruse and counterproductive debate about whether it is fair to use the word “lying” to describe his false statements.
The argument against using the word “lie,” succinctly summed up in NPR's explanation of its editorial decision to avoid the word in favor of euphemisms like “falsehoods” and “untruths,” is that to lie requires intent. I have to mean to mislead you in order to lie to you. If I tell you it's three o'clock when it's really 3:30, I am not lying if my watch is broken; I am only wrong. Because human beings cannot see into one another's minds, it is impossible to say for certain whether Trump intends to mislead. Therefore — so goes the argument goes — a strict concern for accuracy requires that a more modest term be sought.
This is a weak and damaging argument. It is weak because it elevates an abstract problem of epistemology over the functionally obvious truth on whose plane journalism operates; and it is damaging because it does so in a way that is calculated to help liars. Caution is an admirable quality to bring to reporting, but no one expects Fresh Air to be Kant. NPR's criterion for using the word “lie” is so strict that it could only be deployed by someone who had solved the other-minds problem, or else by an actual telepath. (Today on Marketplace, the Dow is down six points and we penetrate the noumenal ego.) If journalists can never say outright that a politician is lying, then the worst consequence lying politicians face is to be tap-danced around by dainty quasi-synonyms like “unsubstantiated assertion.” This is an awfully precious philosophical scruple to sit three pages up from the “Vows” column. The Wall Street Journal can't prove the external world exists, but it still runs baseball scores.
This is why the criterion of self-interest is useful here. We can't prove intention, but we can say that politicians have access to information and a responsibility to stay informed. When they flog their own interests by repeating false statements, intention can be inferred. Maybe Trump is a Berkeleyan idealist, but I'll take my chances that he's just an asshole.
The president of the United States is lying to the world. He is lying casually and deliberately. He is doing it over and over again. To call his lies by any gentler name is ironically to join him in misrepresenting what is happening. What is happening is that the president is lying. The word for a lie is “lie.” The purpose of journalistic ethics is not to produce journalists so morally delicate that they feel more comfortable hedging themselves into half-truths than confidently asserting whole ones.