Dewey became increasingly interested in the philosophy of education and in 1899 published School and Society. To test out his educational theories, Dewey and his wife started an experimental school in Chicago. The school was closed after Dewey became involved in a dispute with the university president, William Rainey Harper. Dewey now moved to Columbia University.

In his books John Dewey outlined his views on how education could improve society. The founder of what became known as the progressive education movement, Dewey argued that it was the job of education to encourage individuals to develop their full potential as human beings. He was especially critical of the rote learning of facts in schools and argued that children should learn by experience. In this way students would not just gain knowledge but would also develop skills, habits and attitudes necessary for them to solve a wide variety of problems. Dewey wrote several books on education and philosophy including Moral Principles in Education (1909), Interest and Effort in Education (1913) and Democracy and Education (1916).

Dewey attempted to show the important links between education and politics. Dewy believed that active learning would help people develop the ability and motivation to think critically about the world around them. Progressive education was therefore a vital part of a successful democracy as it was necessary for people to be able to think for themselves. Dewey also argued that the development of critical thought would also help protect society from the dangers of dictatorship.

Sidney Hook was taught by John Dewey at the College of the City of New York. He wrote in his autobiography, Out of Step: An Unquiet Life in the 20th Century (1987): "A student wandering into a class given by John Dewey at Columbia University and not knowing who was delivering the lecture would have found him singularly unimpressive, but to those of us enrolled in his courses, he was already a national institution with an international reputation - indeed the only professional philosopher whose occasional pronouncements on public and political affairs made news... As a teacher Dewey seemed to me to violate his own pedagogical principles. He made no attempt to motivate or arouse the interest of his auditors, to relate problems to their own experiences, to use graphic, concrete illustrations in order to give point to abstract and abstruse positions. He rarely provoked a lively participation and response from students, in the absence of which it is difficult to determine whether genuine learning or even comprehension has taken place. Dewey presupposed that he was talking to colleagues and paid his students the supreme intellectual compliment of treating them as his professional equals. Indeed, if the background and preparation of his students were anywhere near what he assumed, he would have been completely justified in his indifference to pedagogical methods. For on the graduate level students are or should be considered junior colleagues, but when they are not, especially when they have not been required to master the introductory courses, a teacher has an obligation to communicate effectively. Dewey never talked down to his classes, but it would have helped had he made it easier to listen."

Dewey became influenced by the work of Karl Marx and other left-wing philosophers. Steven Best has argued: "Philosopher Sidney Hook has gone so far as to argue that Deweysim is the genuine fulfillment of Marxism. But the similarities end abruptly on a key point: Marx insisting on the revolutionary overthrow of capitalism, and Dewey embracing pragmatic reform and rejecting Marxism as unscientific utopianism."

While at university Sidney Hook, a socialist, became a devoted follower of John Dewey. "What did impress me about Reconstruction in Philosophy, and later other writings of Dewey, was the brilliant application of the principles of historical materialism, as I understood them then as an avowed young Marxist, to philosophical thought, especially Greek thought. Most Marxist writers, including Marx and Engels themselves, made pronouncements about the influence of the mode of economic production on the development of cultural and philosophical systems of thought, but Dewey, without regarding himself as a Marxist or invoking its approach, tried to show in detail how social stratification and class struggles got expressed in the metaphysical dualism of the time and in the dominant conceptions of matter and form, body and soul, theory and practice, truth, reason, and experience. However, even at that time I was not an orthodox Marxist. Although politically sympathetic to all of the social revolutionary programs of Marxism, and in complete agreement with Dewey's commitment to far-reaching social reforms, I had a much more traditional view of philosophy as an autonomous discipline concerned with perennial problems whose solution was the goal of philosophical inquiry and knowledge."

After the First World War Dewey studied education in Japan and China. He also carried out research in Turkey (1924), Mexico (1926) and the Soviet Union (1928). Dewey's praise of Soviet education brought him much criticism. Other books by Dewey included Reconstruction in Philosophy (1920), Experience and Nature (1925) and The Quest for Certainty (1929).

Dewey was attacked by Leon Trotsky who claimed that although Dewey's ideas had considerable value over previous bourgeois philosophies, he condemned his pragmatism as an insidious apology for capitalism and class collaboration. However, he was praised by Bertrand Russell who pointed out after meeting him for the first time: "To my surprise I liked him very much. He has a slow moving mind, very empirical and candid, with something of the impassivity and impartiality of a natural force."

Dewey was a founder member of the National Association for the Advancement of Coloured People and the American Civil Liberties Union. An early member of the Socialist Party of America, Dewey later joined the Progressive Party and supported Robert La Follette in his attempts to become president. Dewey also joined the League for Independent Political Action. The group, that included Lewis Mumford and Archibald MacLeish, promoted alternatives to a capitalist system they considered to be obsolete and cruel. Sidney Hook argued: "In that period he was indisputably the intellectual leader of the liberal community in the United States, and even his academic colleagues at Columbia and elsewhere who did not share his philosophical persuasion acknowledged his eminence as a kind of intellectual tribune of progressive causes."

Dewey retired from teaching in 1929 and his later years were mainly spent writing. Books from this period include The Quest for Certainty (1929), Philosophy and Civilization (1931), Art as Experience (1934), Liberalism and Social Action (1935), Experience and Education (1938), Freedom and Culture (1939) and Public Schools and Spiritual Values (1944).

The Show Trials of 1936 and 1937 shocked and angered Sidney Hook, a close friend of John Dewey. "The Moscow Trials were also a decisive turning point in my own intellectual and political development. I discovered the face of radical evil - as ugly and petrifying as anything the Fascists had revealed up to that time - in the visages of those who were convinced that they were men and women of good will. Although I had been severely critical of the political program of the Soviet Union under Stalin, I never suspected that he and the Soviet regime were prepared to violate every fundamental norm of human decency that had been woven into the texture of civilized life. It taught me that any conception of socialism that rejected the centrality of moral values was only an ideological disguise for totalitarianism. The upshot of the Moscow Trials affected my epistemology, too. I had been prepared to recognize that understanding the past was in part a function of our need to cope with the present and future, that rewriting history was in a sense a method of making it. But the realization that such a view easily led to the denial of objective historical truth, to the cynical view that not only is history written by the survivors but that historical truth is created by the survivors - which made untenable any distinction between historical fiction and truth-led me to rethink some aspects of my objective relativism. Because nothing was absolutely true and no one could know the whole truth about anything, it did not follow that it was impossible to establish any historical truth beyond a reasonable doubt. Were this to be denied, the foundations of law and society would ultimately collapse. Indeed, any statement about anything may have to be modified or withdrawn in the light of additional evidence, but only on the assumption that the additional evidence has not been manufactured."

As Hook explained in Out of Step: An Unquiet Life in the 20th Century (1987): "The charges against the defendants were mind-boggling. They had allegedly plotted and carried out the assassination of Kirov on December 1, 1934, and planned the assassination of Stalin and his leading associates - all under the direct instructions of Trotsky. This, despite their well-known Marxist convictions concerning the untenability of terrorism as an agency of social change. Further, they had conspired with Fascist powers, notably Hitler's Germany and Imperial Japan, to dismember the Soviet Union, in exchange for the material services rendered by the Gestapo. In order to allay the suspicion flowing from the Roman insight that no man suddenly becomes base, the defendants were charged with having been agents of the British military at the very time they or their comrades were storming the bastions of the Winter Palace. In addition, although the indictment seemed almost anticlimactic after the foregoing, they were accused of sabotaging the five-year plans in agriculture and industry by putting nails and glass in butter, inducing erysipelas in pigs, wrecking trains, etc."

Hook went on to argue: "Despite the enormity of these offenses, all the defendants in the dock confessed to them with eagerness and at times went beyond the excoriations of the prosecutor in defaming themselves. This spectacular exercise in self-incrimination, unaccompanied by any expression of defiance or asseveration of basic principles, was unprecedented in the history of any previous Bolshevik political trial. Equally mystifying was the absence of any significant material evidence. Although there were references to several letters of Trotsky, allegedly giving specific instructions to the defendants to carry out their nefarious deeds, none was introduced into evidence. The most substantial piece of evidence was the Honduran passport of an individual who claimed to be an intermediary between Trotsky and the other defendants, which was presumably procured through the good offices of the Gestapo, although it was common knowledge that such passports could be purchased by anyone from Honduran consuls in Europe for a modest sum."

Sidney Hook was disturbed by the way liberals reacted to the Moscow Show Trials compared to the way that they behaved in response to events in Nazi Germany. Hook, who had little sympathy for Trotskyists as a group, believing that they "were capable of doing precisely what I suspected the Stalinists of doing - if not on the same scale, at least in the same spirit. It was indeed ironical to find the Trotskyists, victims of the philosophy of dictatorship they had preached for years, blossoming out as partisans of democracy and tolerance." However, Hook believed that Leon Trotsky should be given political asylum in the United States: "The right to asylum was integral to the liberal tradition from the days of antiquity. It was shocking to find erstwhile liberals, still resolutely engaged in defending the right of asylum for victims of Nazi terror, either opposed or indifferent to the rights of asylum for victims of Stalin's terror. Of course more than the right of asylum was involved. There was the question of truth about the Russian Revolution itself."

Hook persuaded Freda Kirchwey, Norman Thomas, Edmund Wilson, John Dos Passos, Bertrand Russell, Reinhold Niebuhr, Franz Boas, John Chamberlain, Carlo Tresca, James T. Farrell, Benjamin Stolberg and Suzanne La Follette to join a group that might establish a committee to look into the claims made during the Moscow Show Trials. Hook believed that the best place to hold the investigation was in Mexico City where Trotsky was living in exile and the ideal person to head the commission was John Dewey.

As Jay Martin, the author of The Education of John Dewey (2002), has pointed out: "The leaders of the American committee... realized that a tribunal consisting entirely of Trotsky sympathizers could scarcely achieve credibility on the international stage. What they needed was a group, and especially a chairman, who had an international reputation for fairness and whose integrity could be accepted by liberals, Soviet sympathizers, and intellectuals everywhere. Encouraged by the socialist philosopher Sidney Hook, their hopes soon fastened on Hook's dissertation adviser, the seventy-eight-year-old John Dewey, as the best possible choice for chair. After all, Dewey had been celebrated in the Soviet Union when he went there in 1928 and had been asked by the Socialist Party to run on their ticket for governor of New York. But he was quoted every week or so in the moderate New York Times; he was invited to the White House for dinner; he was the friend of powerful capitalists."

Hook was aware that Dewey had been working on Logic: The Theory of Inquiry for the last ten years and was desperate to finish the book. Hook later recalled in his autobiography Out of Step: An Unquiet Life in the 20th Century (1987): "The first and most important step of the commission was to appoint a subcommission to travel to Mexico City to take Leon Trotsky's testimony. It was crucial for the success of the commission that John Dewey consent to go, because without him the press and public would have ignored the sessions. It would be easy for the Kremlin to dismiss the work of the others and circulate the false charge that they were handpicked partisans of Trotsky. Only the presence of someone with Dewey's stature would insure world attention to the proceedings. But would Dewey go? And since he was now crowding seventy-nine, should he go? Dewey must go, and I must see to it."

Dewey was warned by family and friends of the dangers of becoming entangled in "this messy business." However, he eventually agreed to carry out the task. Dewey wrote to a friend: "I have spent my whole life searching for truth. It is disheartening that in our own country some liberals have come to believe that for reasons of expediency our own people should be left in the dark as to the actual atrocities in Russia. But truth is not a bourgeois delusion, it is the mainspring of human progress."

Upon hearing that John Dewey was willing to head the commission Leon Trotsky gave a speech transmitted by telephone to a large audience at the New York Hippodrome, stating: "If this commission decides that I am guilty of the crimes which Stalin imputes to me, I pledge to place myself voluntarily in the hands of the executioner of the G.P.U."

The Dewey Commission conducted thirteen hearings at the home of Diego Rivera in Coyoacan, from 10th April to 17th April, 1937, that looked at the claims against Trotsky and his son, Lev Sedov. The commission was made up of Dewey, Suzanne La Follette, Carlo Tresca, Benjamin Stolberg, Carleton Beals, Otto Ruehle, Alfred Rosmer, Wendelin Thomas, Edward A. Ross and John Chamberlain. Dewey invited the Soviet Union government to send documentary material and legal representatives to cross-examine Trotsky. However, they refused to do that and the offer for the Soviet ambassador to the United States, Andrei Troyanovsky, to attend, was also rejected.

John Dewey opened the hearings with the words: "This commission, like many millions of workers of city and country, of hand and brain, believes that no man should be condemned without a chance to defend himself.... The simple fact that we are here is evidence that conscience demands that Mr. Trotsky be not condemned before he has had full opportunity to present whatever evidence is in his possession in reply to the guilty verdict returned in a court where he was neither present nor represented. If Leon Trotsky is guilty of the acts with which he is charged, no condemnation can be too severe."

Leon Trotsky and Lev Sedov were defended by the lawyer Albert Goldman. In his opening speech he argued: "We are determined to convince the members of this commission, and everyone who reads and thinks with an independent mind, beyond all doubt, that Leon Trotsky and his son are guiltless of the monstrous charges made against them." According to Jay Martin: "The commissioners raised various questions about the charges against Trotsky. He answered vigorously, with a remarkable command of detail and capacity for analysis... Despite his heavy accent, Trotsky spoke with exceptional clarity, sometimes even with wit and beauty, and always with impeccable logic."

The Dewey Commission was attacked by journals under the control of the American Communist Party. Its newspaper, The Daily Worker, attacked Dewey as a "deluded old man" who was being "duped by the enemies of socialism" and was charged with being "an enemy of peace and progress". An editorial in the New Masses mocked "the so-called impartial inquiry". It added that the "hearings merely presented a rosy picture of Trotsky while blackening the Moscow defendants who implicated him." The Soviet Union government issued a statement describing Dewey as "a philosophical lackey of American imperialism".

According to Sidney Hook, one of the commission members, Carleton Beals, was under the control of the Soviet Union. During the investigation he resigned: "My resignation went in the next morning. Dewey accused me of prejudging the case. This was false. I was merely passing judgment on the commission. He declared that I had not been inhibited in my questioning. He declared that I had the privilege of bringing in a minority report. My resignation was my minority report. How could I judge the guilt or innocence of Mr. Trotsky, if the commission's investigations were a fraud?"

Beals received considerable media attention when he published an article on the case in the Saturday Evening Post: "I was unable to put my seal of approval on the work of our commission in Mexico. I did not wish my name used merely as a sounding board for the doctrines of Trotsky and his followers. Nor did I care to participate in the work of the larger organization, whose methods were not revealed to me, the personnel of which was still a mystery to me. Doubtless, considerable information will be scraped together. But if the commission in Mexico is an example, the selection of the facts will be biased, and their interpretation will mean nothing if trusted to a purely pro-Trotsky clique."

In the article Beals made no attempt to defend the case made against Trotsky at the Moscow Show Trials. Instead he concentrated on stating his belief that Trotsky had been in contact with the people found guilty and executed in Moscow: " I decided to jump into the arena once more with a line of questioning to show Trotsky's secret relations with the Fourth International, the underground contacts with various groups in Italy, Germany and the Soviet Union. Trotsky, of course, had steadfastly denied having had any contacts whatsoever, save for half a dozen letters, with persons of groups in Russia since about 1930. This was hard to swallow."

Beals also accused Leon Trotsky of having an unreasonable hatred of Joseph Stalin: "His mind is a vast repository of memory and passion, its rapierlike sharpness dulled a trifle now by the alternating years of overweening power and the shattering bitterness of defeat and exile; above all, his mental faculties are blurred by a consuming lust of hate for Stalin, a furious uncontrollable venom which has its counterpart in something bordering on a persecution complex - all who disagree with him are bunched in the simple formula of G.P.U. agents... This is not the first time that the feuds of mighty men have divided and shaken empires, although, possibly, Trotsky shakes the New York intelligentsia far more than he does the Soviet Union."

The Dewey Commission published its findings in the form of a 422-page book entitled Not Guilty. Its conclusions asserted the innocence of all those condemned in the Moscow Trials. In its summary the commission wrote: "We find that Trotsky never instructed any of the accused or witnesses in the Moscow trials to enter into agreements with foreign powers against the Soviet Union. On the contrary, he has always uncompromisingly advocated the defense of the USSR. He has also been a most forthright ideological opponent of the fascism represented by the foreign powers with which he is accused of having conspired. On the basis of all the evidence we find that Trotsky never recommended, plotted, or attempted the restoration of capitalism in the USSR. On the contrary, he has always uncompromisingly opposed the restoration of capitalism in the Soviet Union and its existence anywhere else.... We therefore find the Moscow Trials to be frame-ups. We therefore find Trotsky and Sedov not guilty".

John Dewey died in 1st June, 1952.