The left-leaning magazine The Nation has published a list of what it deems America’s all-time, most influential progressives. The list, which you can review for yourself, is very revealing.

For starters, it’s fascinating that The Nation leads with Eugene Debs at number 1. Debs was a socialist. It was 100 years ago this year, in 1912, that Debs ran for president on the Socialist Party ticket.

Today’s progressives get annoyed if you call them socialists. Well, why is a pure socialist the no. 1 “progressive” on The Nation’s list?

Of course, progressives really get annoyed if you suggest they bear any sympathies to communism. That being the case, two other “progressives” on The Nation’s list are quite intriguing: Paul Robeson and I. F. Stone.

Paul Robeson was a proud recipient of the “Stalin Prize.” Even the New York Times concedes Robeson was “an outspoken admirer of the Soviet Union.” When Robeson in 1934 returned from his initial pilgrimage to the Motherland, the Daily Worker thrust a microphone in his face. TheDaily Worker rushed its interview into print, running it in the January 15, 1935 issue under the headline, “‘I Am at Home,’ Says Robeson At Reception in Soviet Union.”

The Bolsheviks, explained Robeson, were new men. He was bowled over by the “feeling of safety and abundance and freedom” he found “wherever I turn.” He discovered sheer equality under Joseph Stalin.

When asked about Stalin’s purges, Robeson retorted: “From what I have already seen of the workings of the Soviet Government, I can only say that anybody who lifts his hand against it ought to be shot!”

Yes, Robeson was deadly serious.

Robeson told the Daily Worker that he felt a “kinship” with the USSR. So much so that he moved his family there.

He also joined Communist Party USA. In May 1998, the centennial of Robeson’s birth, longtime CPUSA head Gus Hall hailed Robeson as a man of communist “conviction,” who “never forgot he was a communist.”

None of this is mentioned in The Nation’s profile, which blasts anyone who dared consider Robeson a communist. Instead, The Nation insists that Comrade Paul was a “progressive.”

And that brings me to I. F. Stone.

Stone is listed at number 26 on The Nation’s list. Stone has been hailed by liberals for decades as the literal “conscience” of journalism—a hero of impeccable honesty. In fact, we now know that Stone, at one time, was a paid Soviet agent.

In their latest Yale University Press work, historians John Earl Haynes, Harvey Klehr, and Alexander Vassiliev conclude that Stone (from 1936-39) was a “Soviet spy.” Also closely studying Stone’s case is Herb Romerstein. In The Venona Secrets, Romerstein likewise concluded that “Stone was indeed a Soviet agent.” One of the stronger confirmations from the Soviet side is retired KGB general Oleg Kalugin, who reported: “He [Stone] was a KGB agent since 1938. His code name was ‘Blin.’ When I resumed relations with him in 1966, it was on Moscow’s instructions. Stone was a devoted communist.”

None of this appears at Stone’s “progressive” profile at The Nation.

And speaking of progressives with communist sympathies, also on The Nation’s list is Margaret Sanger. The Planned Parenthood matron sojourned to Stalin’s Potemkin villages in 1934. “[W]e could well take example from Russia,” Sanger advised Americans upon her return, “where birth control instruction is part of the regular welfare service of the government.”

The Planned Parenthood founder was stunned by the explosion in abortions once legalized by the Bolsheviks. No fear, though. Sanger offered this confident prediction: “All the [Bolshevik] officials with whom I discussed the matter stated that as soon as the economic and social plans of Soviet Russia are realized, neither abortions nor contraception will be necessary or desired. A functioning Communistic society will assure the happiness of every child, and will assume the full responsibility for its welfare and education.”

This was pure progressive utopianism, an absolute faith in central planners.

Overall, the socialists, communists, and Soviet sympathizers on The Nation’s list are dizzying: Upton Sinclair, Henry Wallace, W. E. B. DuBois, Norman Thomas, Lincoln Steffens, Woody Guthrie, Pete Seeger, Tom Hayden, Barbara Ehrenreich, and John Dewey—founding father of American public education.

Thus, I’m compelled to ask: Is this “progressivism?” Is progressivism synonymous with liberalism, or is it much further to left, closer to communism?

I plead with progressives: This is your ideology … Could you better define it, if that’s possible? Or is the definition of progressivism always progressing? Actually, it is always progressing; that’s precisely the problem with this train-wreck of an ever-elusive ideology. The Nation’s list of leading American “progressives” is truly a teachable moment.

Dr. Paul Kengor is professor of political science at Grove City College, executive director ofThe Center for Vision & Values, and author of the book, “The Communist: Frank Marshall Davis, The Untold Story of Barack Obama’s Mentor.” His other books include “The Crusader: Ronald Reagan and the Fall of Communism” and “Dupes: How America’s Adversaries Have Manipulated Progressives for a Century.”

Editor’s note: A longer version of this article first appeared at American Spectator.