Socialism, the idea that workers’ needs are best met by the collectivization of the means of production, didn’t function for Werner. A system in which factories, banks and even housing were nationalized required a planned economy, as a substitute for capitalist competition. Central planning, however, proved unable to meet people’s individual demands, and so rule-breaking and black markets flourished. Werner’s petty theft paled in comparison to the corruption that undermined East Germany from its founding. Eventually, the entire system collapsed; as it did everywhere else, socialism in Germany failed.

Which is why it is strange, in 2019, to see socialism coming back into German mainstream politics: Kevin Kühnert, the leader of the Social Democrats’ youth organization and one of his party’s most promising young talents, has made it his calling card.

Forget the wannabe socialism of American Democrats like Bernie Sanders or Alexandria Ocasio-Cortez. The 29-year-old Mr. Kühnert is aiming for the real thing. Socialism, he says, means democratic control over the economy. He wants to replace capitalism as such , not just to recalibrate it.

In the United States, policies frequently branded as “socialist” — health care for all, a national minimum wage, and tuition-free universities — have very little to do with actual socialism. Big government, yes — but all of them fit comfortably in a traditional free-market economy.

In contrast, German neo-socialism is profoundly different from capitalism. In an interview with my newspaper, Mr. Kühnert took specific aim at the American dream as a model for individual achievement. He said he questioned a system “in which millions start a race, very few make it over the finishing line and then shout back to the others, ‘You could have made it, too!’”