It takes guts to write a book about courage when you have been less than courageous yourself. But that is what Ryan Holiday has done.

Over the past few years, the 34-year-old former marketing executive has transformed himself into what you might call a philosopher-popularizer. His third book, The Obstacle Is the Way, sold more than one million copies and became a bible among players in the N.F.L. and N.B.A. It also became a No. 1 best-seller, as did his 2016 book The Daily Stoic, where he repackaged the wisdom of ancient philosophers for modern life.

Now he’s back with Courage Is Calling, a fast-paced look at what can be learned from some of history’s most courageous individuals. Among them—at least from Holiday’s P.O.V.—are Florence Nightingale, Ulysses S. Grant, Abraham Lincoln, Eleanor Roosevelt, Hannah Arendt, Frederick Douglass, Charles de Gaulle, Winston Churchill, and John Lewis.

“Courage isn’t just the powerless against the powerful,” he tells me by phone while driving around Bastrop, Texas, a small town outside of Austin, where he lives with his wife and two sons and owns an independent bookstore. “It’s not just David and Goliath. Sometimes it’s about Goliath.”

A recent tweet by Holiday.

Which may be why, in addition to that list of so-called Eternals, he includes … Peter Thiel? You know, the megalomaniacal billionaire co-founder of PayPal and Palantir and big-money Trump donor—who also recently hired Sebastian Kurz, the disgraced former Austrian chancellor, to be an investment adviser.

Curiously, Thiel was the subject of another of Holiday’s previous books, Conspiracy, which detailed Thiel’s campaign to destroy Gawker for having outed him. What captivated Holiday about Thiel back then—a willingness to fight back against Gawker’s crossing of journalistic lines—is what he feels places him alongside better-known representatives of courage.

He figures he’s going to get grief, but he doesn’t care. He learned from his mentor, Robert Greene, the self-help guru and best-selling author of The 48 Laws of Power, that if “all your characters are lovable and positive and fun,” your books will be boring.

“I like including at least one or two people that raise eyebrows,” he says. From provocation, he says, comes “a deeper engagement.”

Over the past few years, the 34-year-old former marketing executive has transformed himself into what you might call a philosopher-popularizer.

Holiday is at his most revelatory in the afterword of Courage, where he tackles his own failures to be courageous. Specifically, when he had a chance to stop a boss from posting revenge porn.

It was 2010, and he was 23 and working for Dov Charney (then the still powerful C.E.O. of American Apparel) as the company’s director of marketing. According to Holiday, Charney asked him to leak naked pictures of a woman who was suing him. He told Charney he wouldn’t do it, but Charney quickly found someone else who would. Holiday sees his attempt at courage as having delayed the inevitable, but not stopped it.

“Why didn’t I turn around, walk out the door, and never look back?” he writes. “Why didn’t I quit on the spot?… Why did I still want to keep the job?”

He realized he was afraid to risk his position, his modest income, and his perceived status to stop Charney. He stayed at American Apparel for another three years before quitting, doing his best to keep things going as he witnessed what he calls Charney’s “descent into madness.”

He says he asked his editor if it was “insane” to include the story. But Holiday says it would be “intellectually dishonest” to write about courage and “bask in the reflected glory of other people” while failing to share his truth. “In retrospect, I wish I had done more.”

Since leaving American Apparel and becoming a writer, he believes he’s learned to be more courageous. In 2016, he was a columnist at the Observer, the Jared Kushner–owned Web site (formerly The New York Observer newspaper—once edited by the founder of Air Mail) and decided to write about why Kushner’s father-in-law was unfit for public office.

A post from Holiday’s Instagram account.

“There had been no need for editorial approval of my writing up until that point, but suddenly the paper blocked the publication of my piece,” he writes in Courage. He decided to publish the column elsewhere. He then wrote a column about Breitbart. This column, too, was spiked. He published that on his own also. Then came “serious allegations,” both from the Trump campaign, that one of Holiday’s books had been plagiarized.

“They wanted me to know they would try to ruin me if I didn’t shut up,” he writes. He didn’t give in and cites Marcus Aurelius: “To give in to fear is to deny the talents and skills that got you where you are in the first place. It’s to deprive yourself of the agency you were given at birth.”

Curiously, he also once turned down an offer to become the press secretary to Betsy DeVos, Trump’s billionaire education secretary. He knew the offer was absurd—he was an outspoken Trump critic—but the experience gave him insight into the mindset of those who chose to work in the Trump White House: they lacked the courage to say no to the chance to be adjacent to power and influence.

That goes to the idea of Courage: “Are you willing to put something above money, status, and power?” As he writes, “People would rather be complicit in a crime than speak up. People would rather die in a pandemic than be the only one in a mask. People would rather stay in a job they hate than explain why they quit to do something less certain. They’d rather go along with something that will tarnish their legacy than raise their voice ever so slightly and risk standing alone or apart for even ten minutes.”

We live in a time when genuine courage is in shorter and shorter supply. We’re in the “go along to get along” phase of human existence. But Holiday is not giving up hope. He regularly sends aphorisms to his nearly 500,000 Twitter followers, including one recently from Epicurus, the Greek philosopher: “Remember that what you now have was once among the things you only hoped for.” He tells me, too, that the deputy commanding general of the Special Operations Command wrote to say he is giving copies of Courage to his top 20 officers. And with that, Holiday tells me he has to go. He’s got to get back to work on his next book—about self-discipline.

William D. Cohan is a Writer at Large for AIR MAIL and the author of such best-selling books as The Last Tycoons, House of Cards, and The Price of Silence. He is a founding partner of Puck. His new book, Power Failure, will be published in November