[8] In late adolescence, Stone joined the Socialist Party of America, a political decision influenced by his reading of the works of Karl Marx, Jack London, Peter Kropotkin and Herbert Spencer.

On May 1, 1935, Stone joined the League of American Writers (1935–1943), whose members included Lillian Hellman, Dashiell Hammett, Frank Folsom, Alexander Trachtenberg, Louis Untermeyer, Myra Page, Millen Brand and Arthur Miller.

[11]: 65–66 However, in 1939, following the signing of the Molotov–Ribbentrop Pact, he wrote to a friend that he would do "no more fellow traveling" for the U.S.S.R., and used his opinion column in The Nation magazine to denounce Joseph Stalin as "the Moscow Machiavelli who suddenly found peace as divisible as the Polish plains and marshes".

He was an old-school reporter who did his homework and perused public-domain records (official government and private-industry documents) for the facts and figures, the data, and quotations that would substantiate his reportage about the matters of the day.

I tried to give information which could be documented, so [that] the reader could check it for himself ... Reporters tend to be absorbed by the bureaucracies they cover; they take on the habits, attitudes, and even accents of the military or the diplomatic corps.

He prospected for news nuggets – published as boxed paragraphs in his weekly newsletter – such as contradictions in the line of official policy, examples of bureaucratic mendacity and political obscurantism.

He supported the politics of U.S. President Franklin Delano Roosevelt (1933–1945), especially the progressive reforms of the New Deal (1935–1938) programs FDR was instituting to rescue the U.S. economy from the poverty imposed by the Great Depression which started in 1929.

He alleged inefficient planning and execution, and the business-as-usual attitude, of the industrial and business monopolies — and its tolerance by the U.S. military — that resulted in the tardy production of matériel for the Arsenal of Democracy with which President F. D. Roosevelt said the U.S. would help Europeans and Asians combat the totalitarianism of National Socialist German Workers Party, fascist Italy and Imperial Japan.

On August 4, 1939, Stone along with 400 other writers and intellectuals signed a letter condemning anti-Soviet attitudes in the United States, called for better relations between the two countries, described the USSR as a supporter of world peace, and said "The Soviet Union considers political dictatorship a transitional form and has shown a steadily expanding democracy".

[15][16] Upon hearing of the Pact, Stone repudiated the letter and denounced the actions of the Soviet Union and would criticize it and the CPUSA, which repeated the views of the USSR about the war.

"[17] In the matter of war-production employment, Stone's exposé of alleged institutional racism and anti–Semitism of the FBI's process for vetting job applicants is evident in the semantics of questions meant to discover, identify and exclude political subversives from civil service in the U.S. government.

To the mainstream American reader concerned with the affairs of daily life, Stone reported that, "Questions like these are being used as a sieve to strain anti-fascists and liberals out of the government.

[citation needed] Stone was the Washington, D.C., correspondent for PM, and published a series of feature articles about the Jewish European refugees who ran the British blockade to reach Palestine.

In Underground to Palestine (1948), Stone reported that the political, financial and personal interests of those displaced Jews would have been, in his opinion, better served by emigrating to the U.S. rather than to the Zionist Homeland for the Jewish people promised in the Balfour Declaration.

[26]As a secular Jew, Stone agreed with the nationalist aspirations of Zionism and publicly supported the State of Israel (1948), before the U.S. government granted official recognition.

As a politically moderate Zionist, and like the politician Abba Eban, Stone supported the one-state solution of Israel as a bi-national state that Jews and Arabs would inhabit as equal citizens.

[citation needed] Stone's reportage of the conflict in the Middle East irritated Minister Eban, both for embarrassing him (a politically moderate Zionist) and his government and for dimming the international public image of the State of Israel as a refuge for oppressed peoples.

[27]Consequent to the establishment of British, French, and Russian imperial spheres of influence in Asia Minor, by way of the Sykes–Picot Agreement (1916), the internal politics of the State of Israel became the Arab–Israeli conflict (1948 to date), which the West conflated to the geopolitics of the Cold War (1945–90) with each belligerent party, the U.S. and the U.S.S.R., claiming hegemony over the Middle East.

[28] In the book review article "Holy War" (Les Temps Modernes, June 1967), Stone said that superpower geopolitics are of secondary importance to the discontent of the Arabs and the Jews in the Levant.

[citation needed] In The Independent newspaper in 1992, British journalist Andrew Brown reported that the Soviet Embassy attaché, KGB Major General Oleg Kalugin, said that, "We had an agent—a well-known American journalist—with a good reputation, who severed his ties with us after 1956.

"[14]: 326 In his KGB memoirs, The First Directorate: My 32 Years in Intelligence and Espionage Against the West (1994), about working as a press attaché in the Soviet Embassy in Washington, D.C., Kalugin said that, besides I. F. Stone, he often met with journalists such as Walter Lippmann, Joseph Kraft, Drew Pearson, Chalmers Johnson, and Murray Marder.

On September 13, 1944, the KGB station in New York City transmitted a message to Moscow that Vladimir Pravdin, an NKVD officer working undercover as a reporter for TASS (the Telegraph Agency of the Soviet Union), had sought to communicate with a Soviet agent code-named BLIN, in Washington, DC, but that BLIN had been avoiding a meeting with Pravdin, claiming that his work schedule did not permit the requested meeting.

He reported that Samuel Krafsur, an American NKVD agent codenamed IDE, who worked for TASS in the building that housed Stone's office, had tried to "sound him out, but BLIN did not react.

"[39] In the article "Cables Coming in From the Cold" on the Venona Project transcripts, Walter Schneir and Miriam Schneir said that interpreting the transcriptions is difficult, because of the hearsay nature of the messages; the many steps between a conversation and the sending of a cable; language-translation difficulties; the possibility of an imperfect decryption; and concluded that "the Venona messages are not like the old TV show You Are There [1953–57], in which history was re‑enacted before our eyes.

As evidence, they cited Stone's statement, in a column (November 11, 1951) that responded to New York Herald Tribune reportage about his left wing sympathies, and that he would be unsurprised to read in that newspaper, "that I was smuggled in from Pinsk, in a carton of blintzes".

[14] The FBI claimed that secret agent BLIN must have been someone "whose true, pro–Soviet sympathies were not known to the public", hence, could not have been the journalist Stone,[14] who, on the contrary, far from being "fearful", did not hide his left wing beliefs.

Klehr, Haynes, and Vassiliev said that Stone "assisted Soviet intelligence on a number of tasks, ranging from doing some talent spotting, acting as a courier, by relaying information to other agents, and providing private journalist tidbits and data [that] the KGB found interesting".

That their allegations merely demonstrate that Stone "was a good reporter", and notes that Walter Lippmann is quoted in Spies as having professional contacts with "a Soviet journalist with whom he traded insights and information."

Still, this did not keep Holland from repeating the damaging and long-refuted lie that Herbert Romerstein, former HUAC sleuth, developed after talking with Kalugin, that Moscow Gold [sic] subsidized Stone's weekly.

Composer Scott Johnson makes extensive use of Stone's voice taken from a recorded 1981 lecture in his large-scale musical work, How It Happens, completed in 1991 on commission for the Kronos Quartet.