On Saturday morning I was sitting in the kitchen with my wife, Ann, who was stirring her Cream of Wheat, when out of nowhere she surprised me with a question: “Is not lying one of the Ten Commandments?”

I had to stop and think for a second myself, before answering: “Yes. Thou shalt not bear false witness.”

The fact that the two of us even momentarily struggled over that question is, for me, the worst legacy of the Trump presidency.

You remember the old joke? Moses comes down from Mount Sinai and tells the children of Israel: “Children, I have good news and bad news. The good news is that I bargained him down to 10. The bad news is that adultery is still in.”

Well, I’ve got bad news and worse news: We’re now down to nine.

Yes, this was a historic four years — even one of the Ten Commandments got erased. Lying has been normalized at a scale we’ve never seen before. Hence Ann’s question.

I am not sure how we reverse it, but we’d better — and fast.

People who do not share truths can’t defeat a pandemic, can’t defend the Constitution and can’t turn the page after a bad leader. The war for truth is now the war to preserve our democracy.

It is impossible to maintain a free society when leaders and news purveyors feel at liberty to spread lies without sanction. Without truth there is no agreed-upon path forward, and without trust there is no way to go down that path together.

But our hole now is so deep, because the only commandment President Donald Trump did believe in was the Eleventh: “Thou shalt not get caught.”

Lately, though, Trump and many around him stopped believing even in that — they don’t seem to care about being caught.

They know, as the saying goes, that their lies are already halfway around the world before the truth has laced up its shoes. That’s all they care about. Just pollute the world with falsehoods and then no one will know what is true. Then you’re home free.

The truth binds you, and Trump never wanted to be bound — not in what he could ask of the president of Ukraine or say about the coronavirus or about the integrity of our election.

And it nearly worked. Trump proved over five years that you could lie multiple times a day — multiple times a minute — and not just win election but almost win reelection.

We have to ensure that the likes of him never again appear in American politics.

Because Trump not only liberated himself from truth, he liberated others to tell their lies or spread his — and reap the benefits. His party’s elders did not care, as long as he kept the base energized and voting red. Fox News didn’t care, as long as he kept its viewers glued to the channel and its ratings high. Major social networks only barely cared, as long he kept their users online and their numbers growing. Many of his voters — even evangelicals — did not care, as long as he appointed anti-abortion judges. They are “pro-life,” but not always pro-truth.

For all those reasons, lying is now such a growth industry it deserves its own GDP line: “Auto sales and durables were each down 10% last quarter, but lying grew 30% and economists predict that the lying industry could double in 2021.”

Israeli Bedouin expert Clinton Bailey tells the story about a Bedouin chief who discovered one day that his favorite turkey had been stolen. He called his sons together and told them: “Boys, we are in great danger now. My turkey’s been stolen. Find my turkey.” His boys just laughed and said, “Father, what do you need that turkey for?” and they ignored him.

Then a few weeks later his camel was stolen. And the chief told his sons, “Find my turkey.” A few weeks later the chief’s horse was stolen. His sons shrugged, and the chief repeated, “Find my turkey.”

Finally, a few weeks later his daughter was abducted, at which point he gathered his sons and declared: “It’s all because of the turkey! When they saw that they could take my turkey, we lost everything.”

And do you know what our turkey was? Birtherism.

When Trump was allowed to spread the “birther” lie for years — that Barack Obama, who was born in Hawaii, was actually born in Kenya and was therefore ineligible to be president — he realized he could get away with anything.

Sure, Trump eventually gave that one up, but once he saw how easily he could steal our turkey — the truth — he just kept doing it, until he stole the soul of the Republican Party.

And, had he been reelected, he would have stolen the soul of this nation.

He and his collaborators are now making one last bid to use the Big Lie to destroy our democracy by delegitimizing one of its greatest moments ever — when a record number of citizens came out to vote, and their votes were legitimately counted, amid a deadly and growing pandemic.

It is so corrupt what Trump and his allies are doing, so dangerous to our constitutional system, but you weep even more for how many of their followers have bought into it.

“Lies don’t work unless they’re believed, and nearly half the American public has proved remarkably gullible,” my former Times colleague David K. Shipler, who served in our Moscow bureau during the Cold War, said to me. “I think of each of us as having our own alarm — and it’s as if half of their batteries have died. Lots of Trump’s lies, and his retweets of conspiracy fabrications, are obviously absurd. Why have so many people believed them? I’m not sure it’s fully understood.”

That is why it’s vital that every reputable news organization — especially television, Facebook and Twitter — adopt what I call the Trump Rule. If any official utters an obvious falsehood or fact-free allegation, the interview should be immediately terminated, just as many networks did with Trump’s lie-infested, postelection news conference last week. If critics scream “censorship,” just shout back “truth.”

This must become the new normal. Politicians need to be terrified every time they go on TV that the plug will be pulled on them if they lie.

At the same time, we need to require every K-12 school in America to include digital civics — how to determine and crosscheck if something you read on the internet is true — in their curriculum. You should not be able to graduate without it.

We need to restore the stigma to lying and liars before it is too late. We need to hunt for truth, fight for truth and mercilessly discredit the forces of disinformation. It is the freedom battle of our generation.

Thomas L. Friedman | The New York Times

Thomas L. Friedman, a three-time Pulitzer Prize winner, is an Op-Ed columnist for The New York Times.