The world on Friday lost one of its foremost conservative thinkers. Political philosopher Kenneth Minogue, on a routine flight from Ecuador's Galápagos Islands to the port city of Guayaquil, suffered a heart attack and died at age 82.

As a political philosopher and teacher, Ken helped shape the thinking of thousands of students who passed through his stimulating seminars and classes at the London School of Economics, from 1959 until very recently. I know directly of his intellectual impact because he was my LSE tutor in 1965.

Two years earlier, his first book, "The Liberal Mind," had burst on the intellectual scene, establishing Kenneth Minogue as a political philosopher of the first rank. The book—presented with the rigor, erudition, humor and elegant expression that were hallmarks of his work—set out to understand the roots and portents of liberalism, "an intellectual compromise so extensive that it includes most of the guiding beliefs of modern western opinion."

In "The Liberal Mind" he chastised establishment elites who viewed humanity's every challenge as an opportunity for government intervention. He wanted to find solutions and help those who needed it, but he doubted that suffering could be eliminated by government bureaucracy.

Born in New Zealand, reared in Australia, educated in Britain, a teacher there and in the United States, and an international lecturer, Ken Minogue brought political thought home to generation after generation of students. Those who assumed liberalism's benevolence were challenged, and those skeptical of liberalism were given the intellectual armor for combat.

Yet Ken was much more than a lecturer and teacher. He lent his name and considerable talents to organizations around the world promoting freedom. From 2010 to 2012, he served as the president of the Mont Pelerin Society, an international group of advocates for the free society, of which I am a member. As a frequent attendee at the society's gatherings, Ken could always be counted on to remind us of the past's connection to contemporary issues.

By the time the 50th anniversary edition of "The Liberal Mind" appeared this year, Ken was ready to admit that leftists' "long march through the institutions" had moved more aggressively and more negatively than he had anticipated in the early 1960s. The vitality of the universities and the churches were not as great as he had forecast.

In 2010, he published "The Servile Mind: How Democracy Erodes the Moral Life," a brilliant companion for the book that made his reputation. He was setting out, Ken said in the introduction, to explore "the remarkable fact that while democracy means a government accountable to the electorate, our rulers now make us accountable to them. Most Western governments hate me smoking, or eating the wrong kind of food," he wrote.

But those are "just the surface disapprovals," he added. Deeper ones have to do with how people think and what they believe. "We must face up to the grim fact," Ken said, "that the rulers we elect are losing patience with us."

But Ken still had hope for the West. Last week, at a Mont Pelerin Society meeting in the Galápagos Islands, Ken and I were together on a beach one day when the talk took a bleak turn. His pessimism never lasted long. "Remember," Ken said, interrupting with a felicitous Adam Smith phrase, "there's a lot of ruin in a nation."

He had earlier presented a paper, arguing that societies are necessarily imperfect, and making them perfect is not an option for creatures such as humans. We can, however, reduce the negative effect of policies so that freedom can be expanded. "And in making this judgment, we need to remember the practice of freedom on which our wealth seems to have depended," Ken said. "Solutions that reduce our freedom put modernity itself at risk."

On Friday morning, eight of us hired a guide for a tour of Galápagos beaches. Ken talked about the scale of a single generation as we contemplated giant tortoises more than a hundred years old, and young, fat iguanas, with no natural predators, lazing on the rocks.

Then the discussion turned to human matters—the ratcheting effect of the welfare state and the virtue of America's federal system for experimenting with alternative approaches to problems.

After the tour, our group headed to the airport for a quick flight back to Guayaquil, where we had planned a farewell dinner.

The "quick flight back to Guayaquil" became a desperate ride, with Ken tended by four medical doctors and a priest. By the time the plane landed, our fears had been confirmed.

In Guayaquil, we spent the day making sad phone calls and sending emails to family and friends letting them know that Ken had died.

That night, we gathered for the farewell dinner as planned, with one empty chair and a toast to our departed friend. Ken is in a better place but he did much to improve the one he left behind.

-Ed Feulner is the founder of the Heritage Foundation.