In 2002, Joshua Muravchik, a distinguished scholar, wrote a history of socialism which, he thought, might also be considered an epitaph for socialism.

Beginning in the 18th century, socialism had taken many forms in many countries throughout Europe, Asia, Africa, the Middle East and Latin America. These experiments failed, in many cases spectacularly and tragically.

Surely, socialism was dead and buried. Yes, but like a zombie in a horror movie, it rose from the grave.

Dr. Muravchik’s book was titled: “Heaven on Earth: The Rise and Fall of Socialism.” A new edition, published last month, carries the subtitle, “The Rise, Fall, and Afterlife of Socialism,” and includes a long and edifying epilogue.

I am more than a little troubled that in the United Kingdom, the Labour Party is now headed by Jeremy Corbyn, while in the United States one of the leading candidates for the Democratic presidential nomination is Bernie Sanders. I’m not predicting the two men will be elected to lead their respective nations. But that outcome can hardly be ruled out.

Mr. Corbyn has declared his intention: “to challenge global capitalism.” Richard Seymour, a British Marxist, has praised him as “a radical socialist.”

Mr. Sanders prefers to call himself a “democratic socialist,” a term, Dr. Muravchik writes, “long favored by members of the Socialist Party and others to emphasize their difference with Communism.”

Worth noting: Mr. Sanders’ older brother, Larry, has called him “very socialist – as socialist as Corbyn.” Backers of Mr. Corbyn in the U.K apparently agree. They “gave free facilities for the Sanders effort to round up votes from ‘Democrats abroad’” during his 2016 campaign.

Both politicians have praised such unfree countries as the Soviet Union, Cuba and Nicaragua, and neither has been distressed by the impact socialism has had on Venezuela, which possesses the world’s largest oil reserves, and where 90 percent of the population now lives in hideous poverty.

On the contrary, Mr. Sanders signed a letter of support for Hugo Chavez in 2003, and when the Venezuelan strongman died a decade later, Mr. Corbyn eulogized him “for showing that the poor matter and wealth can be shared.”

Dr. Muravchik brings to bear an unusual perspective because, “Socialism was the faith in which I was raised. It was my father’s faith and his father’s before him.”

Like many idealistic young people around the world then and now, he believed socialism could lead to “an end to exploitation; a new dawn of brotherhood; a different, kinder and more wholesome way of living.”

In the 1960s, he joined the Young People’s Socialist League, eventually becoming its National Chairman. Mr. Sanders belonged to the same group but left for others even further to the left.

Dr. Muravchik conceptualizes socialism as “man’s most ambitious attempt to supplant religion with a doctrine about how life ought to be lived that claimed grounding in science rather than revelation.”

He sees the French Revolution of 1789 as the “manger in which socialism was born.” That culminated in the Reign of Terror and “the Napoleonic bloodbath.”

In the early 1800s, socialists were less revolutionary and more experimental, establishing small communities in the U.S. and England, “led or inspired by Robert Owen” and based on collective ownership. None lasted long.

A few years later, Karl Marx and Friedrich Engels produced what they claimed was a more scientific socialist doctrine, one that “provided an account of man’s history, an explanation of current sorrows and a vision of a redemptive future.”

When the international proletariat refused to conform to Marx’s prophesies, Vladimir Lenin came along to establish a “vanguard” to decide for workers and peasants what was in their best interest. The death toll – due to executions, politically created famines, and the deprivations of the labor camps – would soon be in the millions.

A fact not widely understood: Mussolini learned from Lenin, and Hitler learned from both. It’s no mere coincidence that the Nazi Party was an acronym for National Socialist German Workers’ Party.

Under Communism, Fascism and Nazism, the means of production and other forms of wealth were either owned outright or largely controlled by the state. Those who held political power decided who got what, and for what purposes.

In the late 1970s, Dr. Muravchik writes, “socialism reached its apogee, with communist, social-democratic or Third World socialist regimes governing most of the world.” In country after country, socialism’s ability to alleviate poverty and create wealth for the masses, proved “dismal.” Many socialist regimes evolved into one-party dictatorships and despotisms.

Following the collapse of the Soviet Union in 1991, Russia did not embrace free market capitalism. What wealth Russia possesses is today controlled by President Vladimir Putin and his cronies.

In China, the number of people killed thanks to socialist policies is staggering. In recent years, the ruling Chinese Communist Party has developed a “socialist market economy” that permits entrepreneurship and private ownership. Wealth has been created as a result, but its distribution is among the most unequal in the world. Politically, China is neither democratizing nor liberalizing.

Finally, a word about Scandinavia: Sweden and other Nordic countries experimented with socialism, found it wanting, and returned to capitalism to create the affluence necessary to provide a broad social safety net and an array of welfare benefits to their small, relatively homogenous populations.

In any event, it’s clear that Sweden is not what Jeremy Corbyn has in mind. Is it what Bernie Sanders envisions? To paraphrase Nancy Pelosi, you’ll have to elect him to find out.

Clifford D. May is founder and president of the Foundation for Defense of Democracies (FDD) and a columnist for the Washington Times.