To many, it sounds like a dream: once a month, $500 appears in your bank account, no strings attached.

For some Americans, this situation has become a reality. Over 20 cities and districts across America, from urban Compton outside Los Angeles to the rural Ulster County in upstate New York, are trialling a form of universal basic income (UBI).

Under UBI, every citizen receives a regular sum of money to cover their living costs, almost without exception. A simple idea, but one that could have a revolutionary effect.

For centuries, most people have worked for subsistence. During the Industrial Revolution, wage labour became the norm. But poor conditions prompted workers to demand more, from both employers and the state.

In 1889, German Chancellor Otto von Bismarck introduced the first state pension. Britain followed in 1909, before introducing an unemployment benefits scheme in 1911. Many countries now offer a range of support to citizens, from disability allowances to housing support.

Switching from a means-tested benefits system to one that pays everyone is an enormous leap. But it has steadily been gaining traction, with many seeing it as a solution to increased automation.

One significant supporter is American businessman Andrew Yang, who ran for Democratic presidential nominee for the 2020 US election. His campaign centred around a pledge to give all adult Americans $1,000 per month. Yang quickly became a dark horse candidate, supported by Tech CEOs Jack Dorsey and Elon Musk.

The popularity of the US coronavirus stimulus payments confirmed UBI's place on the agenda.

In Britain, numerous politicians have signed a commitment to the policy, including Greater Manchester mayor Andy Burnham and 25 members of the 60-seat Senedd.

Welsh Liberal Democrats leader Jane Dodds says: "UBI has the potential to transform the lives of people in Wales. It would ensure that people are lifted out of poverty, stress and uncertainty."

Not everyone agrees. Some worry that by paying people equally, UBI might funnel vital funds away from those who need them the most.

Others believe it poses a threat to a capitalist system in which people are paid based on the work they do. Some critics even argue that UBI might make swathes of the population unwilling to work at all, undermining society. As Oxford economist Ian Golden argues: "Delinking income and work... is what lies behind social decay."

In response, UBI's defenders can point to the evidence. A 1970s trial in Canada found only 1% of recipients stopped working, largely to look after families. People on average reduced their working hours by 10%, but largely used the time for studying and job applications.

And a recent two-year trial in Finland found UBI reduced unemployment while having a dramatic effect on recipients' happiness.

Absolutely, say some. Today's welfare systems are humiliating, restrictive and difficult to understand. The support offered by UBI can, in the words of former UK Labour party leader Ed Miliband, "give people more choice in life". Besides, the idea of work as the cornerstone of our daily lives is an outdated one. UBI might let us work less and live more - and who would reject that?

Never, say others. Few deny that unemployment, job insecurity and wealth inequality are big social problems. They must be remedied. But addressing them with UBI is akin to using a plaster to treat cancer. The enormous technological changes that our society is undergoing will require a complete reconsideration of what work and life should be - not a headline-grabbing quick fix.