As Lawrence H. Summers, the former Treasury secretary and onetime top economic adviser to President Obama, told me, paying a $5,000 universal basic income to the 250 million nonpoor Americans would cost about $1.25 trillion a year. “It would be hard to finance that in a way that wouldn’t burden the programs that help the poor,” he said.

The popularity of the universal basic income stems from a fanciful diagnosis born in Silicon Valley of the challenges faced by the working class across industrialized nations: one that sees declining employment rates and stagnant wages and concludes that robots are about to take over all the jobs in the world.

That might lie in our future — I will devote my next column to discussion of such a universe. But it’s certainly not our present. Men at their prime working ages, 25 to 54, have been falling out of the labor force since the 1960s. Still, today more than eight out of every 10 Americans in their prime are working.

Work, as Lawrence Katz of Harvard once pointed out, is not just what people do for a living. It is a source of status. It organizes people’s lives. It offers an opportunity for progress. None of this can be replaced by a check.

A universal basic income has many undesirable features, starting with its non-negligible disincentive to work. Almost a quarter of American households make less than $25,000. It would be hardly surprising if a $10,000 check each for mom and dad sapped their desire to work.

A universal income divorces assistance from need. Aid is fixed, regardless of whatever else is going on. If our experience with block grants serves as precedent, it is most likely to become less generous over time.

To libertarians this will sound more like a feature than a flaw, but replacing everything in the safety net with a check would limit the scope of government assistance in damaging ways. Say we know the choice of neighborhood makes a difference to the development of poor children. Housing vouchers might lead them to move into a better one. A monthly check would probably not.