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Answer: Although complicated, totally relative and exhausting to wrestle with elsewhere, this concept is never up for debate under the watch of Alex Trebek on “Jeopardy!”

Question: What is truth?

In the wider world, it’s a question that seems slipperier at every turn. Postmodernists declared the truth socially constructed. The election of President Trump — who made 8,158 false or misleading claims in his first two years in office — suggested that they were right. We arguably live in an anti-expertise world. Americans can’t tell opinion from fact. Truth has always been valuable, but its present scarcity makes it feel especially precious.

So when Trebek announced Wednesday that he had been diagnosed with Stage 4 pancreatic cancer, which carries a particularly low survival rate, it felt like we were grieving the potential loss of more than an avuncular quiz-show host. The loss of Trebek means the loss of a zone where the truth is clear and uncontested.

Since 1984, Trebek has dispensed truths at a dime a dozen. The show’s format, inverted from the standard trivia setup, puts all the answers right there on the board — 30 truths at a time for contestants to discover. All they have to supply is the question.

That question must be precisely worded. In Trebek’s world, there is no room for the hedging, fudging and squidging of the truth that dominates everyone else’s: “Who is: Bronte?” Yes, but which one? “What is: ‘Gangster’s Paradise’?” Oh, I’m sorry, we’re looking for ‘Gangsta’s Paradise.’”

These standards slide once we leave the “Jeopardy!” set, where canny manipulators get away with plenty worse than a misarticulated second syllable. The best a contestant can do with Trebek in the room, though, is hoodwink the host until a commercial break. On the rare instances that points are awarded improperly, the record is always promptly corrected and the scores adjusted before things can get too out of hand.

Trebek embodies something increasingly rare: a universally accepted authority. Yes, a panel of judges spot-checks in real time, but the audience never sees those people do the hard work of interpreting what is and isn’t truth. Trebek is the face, and his effortless “correct” or “incorrect” is the voice of the facts.

As “Jeopardy!” took off, Trebek parlayed his authority into hosting other gigs that attempted to establish an objective reality: the National Geographic Bee, gubernatorial debates, NBC’s “To Tell the Truth.” “Jeopardy!” legend Ken Jennings pointed out on Twitter following Wednesday’s news that Trebek is, in a way, the “last Cronkite.” You can’t help but trust him.

It’s painful to contemplate losing the man who gives us the game-show version of “That’s the way it is.” Without Trebek, we’ll have fewer refuges from the messy grays and half-truths that have come to define so much of public life.

Trebek has, of course, vowed to beat the cancer. In his announcement, he chided his fans for even thinking about counting him out. That gentle reproach is familiar to any regular viewer of “Jeopardy!”

Trebek’s mastery of subtle shade is always on greatest display with the show’s dreaded Triple Stumper — a prompt none of the contestants is able to answer. When no one buzzes in, Trebek nearly without fail asks with disappointment: “Nobody?”

Not everybody is expected to know all the truth all the time. But at least somebody ought to.

Read more:

Megan McArdle: We finally know for sure that lies spread faster than the truth. This might be why.

Ruth Marcus: Welcome to the post-truth presidency

Barton Swaim: Politics has always been post-truth. Trump’s just honest about it.