My most vivid recollection of Kagan in the classroom is from a seminar on the Peloponnesian War. Referring to the Athenian rascal Alcibiades, Kagan asked: “And what does Plutarch tell us about Alcibiades?” It was a rhetorical question: “HE WAS VERY ATTRACTIVE!” Kagan exclaimed, pointing a finger in the air — and noting that the features we look for in our national leaders haven’t changed all that much.

Kagan’s unapologetic advocacy for the study of Western civilization and for protecting the right to air unpopular and even abhorrent views made headlines not just at Yale but around the country. He never understood the tenured academics who claimed to be afraid to speak up, and he loved to say that he kept making trouble — and getting promoted.

Kagan’s passing comes just four months after the death of another legendary Yale teacher, the diplomat Charles Hill, who died in late March at the age of 84. They had much in common, and they are a dying breed on the country’s university campuses. Both were unapologetic believers in and advocates for American exceptionalism — Hill as a foreign service officer and then as a top State Department official; Kagan in the classroom, where he laid out how the Greeks and their intellectual descendants, including the American founders, were different from most other societies. It’s not a popular view in academia. Kagan liked to joke, “There are places in this university where a motion to wish me a happy birthday would get a close vote.”

Both Hill and Kagan were unabashed generalists who pushed back against the academic trend toward early specialization. They urged students to see the connections between the ancient and the modern, and among business, politics and government. Hill demonstrated the interconnectedness of those fields by teaching courses on everything from “The Architecture of Power” to “Baseball as Grand Strategy.” He would joke that Yale, to its detriment, now hired only scholars of increasingly niche topics like Indonesian basket-weaving.

In a speech delivered upon his retirement in 2013, Kagan suggested that specialization is the enemy of freedom, which requires for its maintenance a citizenry with a broad education. Describing ancient times, he said, “Servants were ruled by others, so free men must take part in their own government. Servants specialized to become competent at some specific and limited task, so free men must know something of everything and understand general principles without yielding to the narrowness of expertise.”

Kagan might have been the world’s leading classicist, but his career was a protest against compartmentalization. He is probably the only scholar of antiquity to have served as Yale’s director of athletics. In fact, in his four and a half decades at Yale, he served in virtually every position imaginable — head of the classics department, dean of Yale College, master of the residential college Timothy Dwight, and emeritus professor of classics and history.

Both Kagan and Hill took students seriously but refused to pander to them. They cared enough about them to try to mold them from coddled and entitled teenagers into functioning adults. I still remember Kagan asking for an explanation from a classmate who had delivered a seven-page paper when he had been asked for four pages. Kagan told the student to familiarize himself with the old saw about the man who wrote a long letter because he didn’t have the time to write a short one.

Over tea one afternoon during my senior year, Kagan told me to get married and have children early — and then to go off and have a career. He knew that many ambitious women would also want marriage and a family, and he was willing to give a steer even if the advice was impolitic. It was also clear that, for all his professional achievements, he valued his family above all. He told me in this same conversation that when his son Bob left for college — at Yale, where Kagan himself was teaching — he burst into tears every time he passed his son’s empty bedroom. So, Kagan took a position leading Yale’s Timothy Dwight College, where Bob was living.

Kagan spent a half-century trying to buck the trends making a national mockery of today’s college campuses. He was the engine behind Yale’s groundbreaking 1974 report affirming the centrality of free expression on campus. That spring, student protesters had shut down a debate with the Stanford physicist and eugenics proponent William Shockley. It was not that Kagan was a defender of Shockley’s views, but he was furious with the university’s lackadaisical response to what he saw as an effort by students to stifle open debate. He spent the summer of 1974 cooking up a searing indictment of his boss, university president Kingman Brewster. In the fall, Kagan gave a speech to the Yale Political Union arguing that the administration had been unwilling “to pay the price” to protect free speech.

In response, Brewster charged the eminent historian C. Vann Woodward with producing a report on the state of free speech on campus. And Yale broke ground when it adopted the report’s conclusion: While some speech would inevitably cause “shock, hurt, and anger,” the report stated, the right to “think the unthinkable, discuss the unmentionable, and challenge the unchallengeable” was more important.

Yale, along with many other college campuses, has now abandoned that principle in deed if not in word, but the shadow of the Woodward report has made the university’s self-justifications more challenging and more embarrassing. Watching the weak-kneed university president, Peter Salovey, work to tamp down an absurd controversy over Halloween costumes by insisting that free expression and “an inclusive community” are not mutually exclusive has at least been amusing, since the premise of the Woodward report is that, in fact, prized values inevitably come into conflict.

President George W. Bush awarded Kagan the National Humanities Medal in 2002 for his scholarship on “the glories of ancient Greece,” but it was the lessons Kagan drew from ancient times and applied to our own that made his thinking a part of the intellectual foundation of Bush-era foreign policy. He argued that democracy was “one of the rarest, most delicate and fragile flowers in the jungle of human experience,” and that the United States alone had the economic resources and political power to protect it.

Kagan was irrepressibly positive. Having arrived in the United States from Lithuania after his father’s death when Kagan was two, and then grown up in the modest Brownsville neighborhood of Brooklyn, he marveled at his good fortune and what became of his life. And even as he bemoaned the state of academia, he remarked with astonishment once, “My students just keep getting better and better!”

On the big issues he cared about, though — inculcating an understanding that the goal of a liberal education was defense of free thinking, a free exchange of ideas and, ultimately, a free society — he was pessimistic. He didn’t think Yale offered a vigorous enough defense of the husband-and-wife professorial team that came under attack in 2015 for suggesting that the university should not police the Halloween costumes students chose to wear. “It’s very hard to recover from this kind of surrender,” he told me at the time. “Surrender to fear, to the prospect of violence and obloquy … that’s what happens when you allow bullies to bully you.” Then he shrugged and said with a wry smile, “It’s ‘progress.’”

Hill, as it turned out, offered the opening remarks for Kagan’s 2013 retirement speech. “Emerson said that an institution is the length and shadow of a man,” Hill told a packed audience in Yale’s William L. Harkness Hall. “Yale, the discipline of history and the nation have all felt the impact of Don Kagan, and each of these institutions will come to recognize that impact in the years ahead even more than they do now.”

The torch now passes to his students to take up the fight.