Everything I know about history, I learned from Thomas B. Costain.

That would truly annoy Frank Wright, the exceptional high school history teacher from whom I also learned a lot. I tell the Costain story often. It is mostly the truth.

Canadian journalist and editor Thomas B. Costain published his first best-selling historical novel, For My Great Folly, at the age of 57. He had toiled in the writing trenches for most of his working life before Folly. Mr. Costain’s fiction relied so heavily on historic events that one reviewer said “it was hard to tell where history leaves off and apocrypha begins.” Mr. Costain made the story of Joseph of Arimathea and the lowly Basil of Antioch come alive for millions of Americans, including me. The Silver Chalice may have been the first historical novel I ever read.

I had read Chalice, the Tontine, Below the Salt, and the Last Plantagenets before leaving for college. My mom, a Swarthmore alum, also knew American writer James A. Michener and introduced me to his work as well.

Mr. Michener penned some of the best known sagas in literature, novels that spanned the lives of uncounted generations in exotic or previously under reported locales. He was known for his meticulous research which let him work the entire history of each region into his stories. I can almost say I know more about the Chesapeake Bay from reading Mr. Michener’s Chesapeake than from growing on the water there.

The Italian government lauded biographical novelist Irving Stone for the way he highlighted Italian history in the Agony and the Ecstasy, the life of Michelangelo Buonarroti.

So.

How do we separate fact from fiction when our favorite novelists leaven their rising stories with actual history in search of a truth? Or in search of a good story?

It is hard, after reading Costain, not to mistake the Grail story as truth. It is hard, after reading Michener, not to mistake the many generations of the Buk, Bukowski, and Lubonski families as real.

Fast forward.

Jon Stewart is a brilliant satirist. Pew Research Center’s search for the most admired American journalist has Mr. Stewart, the fake news anchor, at Number 4, tied with actual news anchors Brian Williams and Tom Brokaw of NBC, Dan Rather of CBS, and Anderson Cooper of CNN. Dan Rather? OK, it was a 2007 poll. The Daily Show does have pieces of substantive news but satire can’t handle the whole truth and Mr. Stewart has repeatedly insisted that he is only a comedian on a fake news show.

Monologist Mike Daisey played the Lane Series at the Flynn Theater in Burlington, Vermont, this weekend. His The Agony and the Ecstasy of Steve Jobs has caused a national foofah over what is and what isn’t true in his monologue about Apple and its manufacturing practices in China. In January, NPR’s This American Life and its host, Ira Glass, published a critical 39-minute story that detailed the appalling Chinese iPhone plants, a program adapted from Mr. Daisey’s theatrical monologue.

Last weekend, Mr. Glass retracted the story.

The most admired reporter of our times, Edward R. Murrow said, “To be persuasive we must be believable; to be believable we must be credible; to be credible we must be truthful.” From Costain to Michener to Stewart to Daisey to Survivor we’re blurring the line between truth and fiction.

We in the news business must be truthful. But most of all, we must remember that entertainment has no such need.

“Get the facts, Dick,” Frank Wright would tell me. “It’s not the truth without the facts.”

Of course, I’m not sure Mr. Wright ever watched “reality TV.”