Radicalism becomes invisible, paradoxically, in its victories. When the Americans with Disabilities Act (ADA) was signed into law in 1992 by Republican President George Herbert Walker Bush, few thought back to Helen Keller, the socialist and early deaf advocate. Few remembered the bohemian radical Randolph Bourne, who penned the pathbreaking essay “The Handicapped” in 1911. Few recalled the “Rolling Quads,” a band of sixties-era Californian quadriplegics led by Ed Roberts who repurposed power wheelchairs meant for hospital use and took them out into the streets, showing up en masse at a Berkeley city council meeting in 1969 to demand that the city cut ramps in its five-inch curbs, making the City's sidewalks wheelchair-accessible for the first time. Few recalled Black Panthers bringing soul food to the disabled occupiers of the San Francisco offices of the Department of Health, Education, and Welfare in 1977. But disability rights were won by a mosaic of such alliances, which mobilized people facing a range of adverse conditions, from multiple sclerosis to cerebral palsy. In 1988, protests broke out at Gaulladet University, a federally chartered institution serving the deaf since 1864, to demand appointment of its first deaf university president, with thousands signing “Deaf President Now” and marching on Congress, successfully. Two months later, the ADA was introduced in Congress. In 1990, members of Americans Disabled for Accessible Public Transit (ADAPT) abandoned their wheelchairs for a “crawl-up” of the Capitol steps to demand access as a right, each carrying a scrolled Declaration of Independence. Once objects of disgust or pity, the disabled had overcome stigma and shame to imagine a world of access and wrest a transformation that affected resource allocations, not just sensibilities – changing, in fact, the very physical design of American life.

Although the radical left has occupied very few positions of high office in American politics since the Second World War, it has had a catalytic role in American life. Dwight Macdonald once distinguished liberals who see themselves as “the left opposition within the present society” from radicals who seek a new society altogether. If radicals have not obtained a wholly new society on the scale some have dreamt, the past seven decades have in many instances seen a mutually reinforcing dynamic at work, with radicals pushing for sweeping, previously unthinkable alterations until liberals – or even conservatives, once the outré passes into the ocean of common sense – enact reforms.