The American Spirit: Who We Are and What We Stand For, by David McCullough, Simon & Schuster, 2017.

The slim new book — scarcely 150 pages — from David McCullough, The American Spirit, is a collection of transcripts from some of the speeches the author has given at various venues over the last 30 years. It’s the first book of its kind in Mr. McCullough’s long publishing career: even readers who have eagerly read his histories and biographies will have missed these addresses, most of which were delivered at college graduation ceremonies or private functions such as addresses to Congress.

Those readers will be interested in everything here, because this is Mr. McCullough working in a different and often fascinating register, shifting his emphasis from research to rhetoric. As the author notes in his introduction, he’s been giving speeches for more than 50 years (and in all 50 states), and this is borne out in every section of The American Spirit. Even the slightest of these pieces show a practiced ease, the cadence of a speaker accustomed both to receiving attention and deserving it.

Mr. McCullough recalls the simple advice The Guns of August author Barbara Tuchman gave to historians: “Tell stories.” And in even the briefest of these speeches, he puts that advice into practice, whether he’s telling a joint session of Congress about John Quincy Adams (“the most superbly educated and maybe the most brilliant human being who ever occupied the executive office”) and reminding them that “giants come in all shapes and sizes,” or pointing out to the graduates of Michigan’s Hillsdale College just how young most of the founding fathers were when they won independence from the British. (“They were, as we would say, winging it.”) While speaking to the graduates of Boston College in 2008 about the heroic Massachusetts Sen. Charles Sumner, he stresses the value of omnivorous reading. A talk at a conference for historic preservation in Providence veers into a hymn of praise for Abigail Adams, working long days at her family’s farm in her husband’s absence and at the end of every day sitting at her kitchen table, taking up her quill pen, and writing “some of the most thoughtful, telling letters of any American of the time.”

Mr. McCullough is a two-time winner of the Pulitzer Prize, a two-time National Book Award winner, and a recipient of the Presidential Medal of Freedom, and a large part of that fame rests on his uncanny talent at drawing personal elements out of historical records, making the characters in his books — Theodore Roosevelt, Harry Truman, John Adams — as vivid as their times. And even when tasked to give brief occasional remarks, that talent is always working. In addition to broader sketches of the great heroes and heroines of American history, there are lesser-known figures in these pages, no less heroic but lacking, so far, a David McCullough to put their incredible life stories on the bestseller lists.

One such figure is the Rev. Manasseh Cutler, recalled to the graduates of Ohio University in 2014 as a man who was “a university unto himself” and evoked in unabashedly personal tones. “As a resident of Massachusetts, I was pleased to find he lived in Ipswich, north of Boston, where he preached for more than fifty years,” Mr. McCullough writes. “Then to my complete surprise, I read that shortly after he was married, he ran a store on the island of Martha’s Vineyard, only a few miles from where I live and work.”

For Mr. McCullough in these speeches, history is always just this immediate and personal, and he’s constantly warning his listeners not to take its truths as preordained certainties. The Declaration and the war of Independence were mind-boggling risks, taken by men and women who were full of doubts. The country itself was an experiment, one that could easily have gone wrong. It’s this ear for the sheer contingency of events that has always made Mr. McCullough’s books such gripping reading, and it’s a very pleasant surprise how often he manages to infuse it even into the text of a 15-minute speech.

But there’s more going on in these pages, as is hinted in the author’s references to Republican Sen. Margaret Chase Smith, who stood up to the creeping tyranny of McCarthyism, ringingly telling her listeners: “I don’t want to see the Republican Party ride to political victory on the four horsemen of calumny — fear, ignorance, bigotry and smear.” In the text of a talk at a naturalization ceremony at Monticello in 1994, he assures his audience of new citizens, “I welcome you, our new fellow Americans. The nation is richer for you.” In irritated, avuncular tones, he urges the graduates of Union College in Schenectady: “Let’s do something about public education. Let’s stop the mindless destruction of historic America. Let’s clean up our rivers and skies, and while we’re at it, let’s clean up our language — private and public and on the airwaves.”

The drift here couldn’t be clearer, despite the author’s courteous discretion. As he puts it in his introduction, his selection of these particular speeches out of many thousands was intended not merely to “tell stories” but to tell a particular kind of story, to stress the importance of history as “an aid to navigation” and to remind his readers of things the bitter rancor of the day’s news might have made them forget: that the country has faced times of “uncertainty and contention” at many points in its past, and that the “American spirit” of the collection’s title is ultimately stronger than the bitterness of alternative facts and fake news. The book is a reminder of the better angels of our nature.