Why it is always a mistake to call someone a liar

It is not just a factual description that is hard to prove – it's also an insult

A protester in London yesterday carries a placard with a mock-up of Boris Johnson as Donald Trump (Reuters)

If I want to render my Twitter account unusable for a few days, all I have to do is to repeat one of my most unpopular opinions, namely that it is a bad idea to use the words “lie” or “liar”.

My argument is that we do not have windows into each other’s hearts, and so when someone says something that is untrue it is hard to be sure they are doing it deliberately.

“Liar” is not just a factual description that is hard to prove, however, it is also an insult, making a judgement about someone’s moral character. I don’t think it should be used in news reporting, and I think it weakens commentary. Better just to state the facts and let the reader judge.