“I think Donald Trump sees himself larger than life,” said former House Speaker John Boehner recently. “He kind of reminds me of Teddy Roosevelt, another guy who saw himself larger than life.”

As a Roosevelt scholar, I beg to differ. Theodore Roosevelt did not see himself as larger than life; he was larger than life. We don’t celebrate him because of his ego; we celebrate him because he was a hero who embodied and championed the virtues that we Americans admire: honesty, courage, compassion, and resolve.

Roosevelt held everyone to a high standard, but he held himself to the highest standard of all.

Even as a child, he worked hard to make himself a better person. To strengthen his body, he exercised daily and learned to box and hunt. To expand his mind, he devoured books on every subject, sometimes two or three per day. Above all, he worked to fortify his character. “Bodily vigor is good, and vigor of intellect is even better,” he wrote, “but far above both is character.” A person of character “must not steal, he must not be intemperate, he must not be vicious in any way; he must not be mean or brutal; he must not bully the weak,” he expounded. “He must be brave and energetic; he must be resolute and persevering.”

T.R. (he never liked “Teddy”) was all these things. When robber baron Jay Gould corrupted a New York State judge, T.R. demanded an investigation. When a drunken gunslinger roughed up a saloon in the Dakota badlands, T.R. knocked him cold with his bare hands. When the United States went to war against Spain, T.R. quit his government post and personally led the charge up Cuba’s San Juan Heights. When a would-be assassin put a bullet in his rib, T.R. postponed medical treatment until he had finished his 80-minute speech.

But Roosevelt didn’t just cultivate his own personal character; he also elevated America’s national character. As president, he used his bully pulpit to urge people to be brave and selfless and good, for he believed that “whether this country goes up or goes down will depend in the last analysis upon the character of the average American.” In those days, the United States was still an emerging power, but T.R. promised that if the American people remained courageous and steadfast, they would soon lead the world. “We must dare to be great,” he proclaimed, “and we must realize that greatness is the fruit of toil and sacrifice and high courage.”

A century before the Internet, when crossing the ocean required several days at sea, Roosevelt anticipated a time when “nations grow to have ever wider and wider interests, and are brought into closer and closer contact.” He urged Americans to meet the challenges of globalization fearlessly and to avoid succumbing to the “fossilized isolation” of the fading Chinese empire, “content to rot by inches in ignoble ease within our borders, taking no interest in what goes on beyond them, sunk in a scrambling commercialism; heedless of the higher life, the life of aspiration, of toil and risk.”

How ironic that in the 21st century, China has reinvented itself as an aggressive, globally engaged superpower while the future president of the United States promises to make America “great again” by retreating into safety behind “a great, great wall.” Theodore Roosevelt called for Americans to be courageous; Donald Trump tells us to cower in fear. “Donald Trump will protect you,” announced one of his campaign ads. “He is the only one who can.”

That too is ironic, for Trump is not a brave man. Roosevelt wrote books on military history and risked his life in battle. Trump second-guesses generals but avoided military service when duty called. “I think I’ve made a lot of sacrifices,” he rationalized in an interview. “I’ve created thousands and thousands of jobs, tens of thousands of jobs, built great structures.” In a speech to war veterans he lauded himself for being “financially brave.”

T.R. would have scoffed at such excuses. “The people who pride themselves upon having a purely commercial ideal are apparently unaware that such an ideal is as essentially mean and sordid as any in the world,” he wrote. Roosevelt preferred those who devoted themselves to public service, whether in military, government, or private life. He admired people who played fair, stood up to bullies, and exhibited the character traits he prized: honesty, courage, moderation, generosity, and self-discipline.

Mr. Trump doesn’t give a damn about his own character or anyone else’s. He fabricates falsehoods with shameless abandon. He flaunts his wealth, shuns self-discipline, and takes pleasure in bullying the weak. He exploits unfair opportunities and then brags about how he beat the system. He boasts of generosity but is notoriously stingy and takes credit for others’ charity. His idea of courage is a risky business venture. John Boehner was right about one thing. Donald Trump does see himself as larger than life. “I’m the only one who can fix it,” he declared in a campaign speech. “We will take back this country for you and make America great again.”

But Boehner was very wrong about Theodore Roosevelt. When T.R. spoke at Gettysburg, Pennsylvania more than a century ago, he said something quite different about what it means to be a great nation. “National greatness is of slow growth,” he said, “for it is based fundamentally upon national character, and national character is stamped deep in a people by the lives of many generations…So we, the people, can preserve our liberty and our greatness in time of peace only by ourselves exercising the virtues of honesty, of self-restraint, and of fair dealing between man and man.”

Michael Wolraich is the author of Unreasonable Men: Theodore Roosevelt and the Republican Rebels Who Created Progressive Politics. He tweets at @wolraich.