Labor Day can seem like a holiday that belongs to another era. That is not because the trade union movement is no longer relevant, nor does the impulse to honor work and workers ever lose its importance. But the word "labor" once defined an entire culture, with its "names, battle slogans, and costumes," in Karl Marx's phrase. Where did it go? The labor movement had its symbols, from politically charged clothing to badges to the holidays in May and September; its structures, from picket lines to unions to worker-owned insurance companies; its rhetoric, from the manifestos of agitators to the leaflets of organizers to the songs of Woody Guthrie; its ethic, defined as solidarity. Millions continue to hold membership in unions, which continue to protect the rights of workers, but the triumph of the labor movement consisted in its becoming a feature of a social landscape that is taken for granted. It was nifty when workers' apparel - blue jeans - and equipment - pick-up trucks - became items of upper class fashion, but the shallow victory implied a substantial defeat. Labor stopped being a force for political change, much less for social justice. What happened? The 19th-century dream of a workers' vanguard leading to a better world was both betrayed and realized, and in each case, labor was undercut. The betrayal occurred when tyrants, in advancing the cause of "the people," actually advanced themselves. The "dictatorship of the proletariat" turned out to be mere dictatorship. Yet the discrediting of the vision of Karl Marx by the 20th-century communisms that claimed him does not vitiate the original vision. Echoing what Mahatma Gandhi once said of Christianity, Marxism has yet to be really tried. The realization of the workers' dream occurred, across the same decades of the 20th century, when regulated capitalism made its adjustments, and a vast population of working people was able to lay solid claim to the middle class. But affluence had an inherently co-opting effect, as was powerfully displayed during the American civil rights movement, when the labor virtue of solidarity was trumped by racism, and union members mostly found themselves on the wrong side of history. The curious phenomenon of "Reagan Democrats" saw workers recruited into a reactionary political movement that undercuts their own interests. Meanwhile, the human significance of work was undergoing a massive cultural mutation, as traditional industry gave way to high technology, skill to mechanization, manufacturing to information, and economic nationalism to globalization. Marx worried about the control of the means of production, but what is control when the factory is replaced by the keyboard as the center of invention? For 200 years, "capital" was decisive, but then along came "intellectual capital." Goodbye borders. Goodbye regulation. Welcome to the free market, a free-for-all that destroys freedom. The very conditions of transcendent inequality that gave rise to the labor movement in the first place are now being rapidly re-created on a global scale, with unions reduced to the role of sputtering kibitzers. In the United States, the most revealing failure of the labor movement to live up to its foundational ideal involves labor's role as a pillar of the military-industrial complex. The engine of the American economy is defense spending. For two generations, but especially since the end of the Cold War, the nation has cannibalized itself by investing its best minds and most of its treasure in a profoundly counterproductive military establishment. Usually this is blamed on the so-called "iron triangle" of corporations, Congress, and the Pentagon, which keep trillions of dollars circulating through the unbroken loop. But the labor movement has long been an essential part of this corrupt system, with union lobbyists playing their crucial role in keeping the lucrative defense contracts coming. What would have happened at the end of the Cold War, when the expected "peace dividend" might have rescued education or rebuilt the nation's infrastructure, if union leaders, backed by the grass-roots labor movement, had demanded an end to the Pentagon boondoggle? The conversion of a military-based economy, serving no real purpose beyond its own enrichment, to an economy of authentic productivity would have transformed foreign policy in the nick of time (no war in Iraq), and provided resources for homefront infrastructure (no failed dikes in New Orleans, or collapsed bridges in Minneapolis). It did not happen, for a lot of reasons - one of which is the hollowed out commitment of a movement that should have known better. What this nation needs is a revitalized reason to celebrate Labor Day. James Carroll's column appears regularly in the Globe.