Young pessimists can save the world.

The most telling words about a country are often those that are impossible to translate. In the case of Germany, one such word is “Zweckpessimismus.” It means, roughly, pessimism on purpose — the attitude of expecting the worst in order to be able to feel relief when the worst, oh lucky us, does not occur.

People displaying Zweckpessimismus are often annoying. They tend to ruin other people’s fun with their “what can go wrong will go wrong” posture. But Zweckpessimists mostly have a point, like parents warning children against stupid behavior.

This past year, it was the other way around: The Fridays for Future movement, which is stocked and led by young people, is defined by pessimism on purpose toward older generations and their role in driving climate change. Emerging a year ago from the protests of a Swedish teenager, Greta Thunberg, Fridays for Future and its vociferous warnings of an imminent eco-apocalypse has swept across Northern Europe, and is particularly strong in Germany. In June, 500 students linked arms around the Reichstag in an attempt to block legislators from exiting for their summer recess.

It is as easy as it is wrongheaded to ridicule the movement. The young have not only the right to be morally rigorous, but the duty. With age comes intellectual routine, and with intellectual routine comes complacency and operational blindness. It often takes a newcomer’s sense of astonishment to see and break a society’s psychological and social deadlocks — be it the antiwar marches in Washington half a century ago, or the climate strikes in Stockholm and Berlin today.

As a member of an older generation, I am thankful for this new youthful energy. But at the risk of coming across as a lecturing parent, I also have some advice: Zweckpessimismus only goes so far. We need optimism too. Otherwise, your steady calls of alarm risk becoming a complacent routine in itself.

At least in Germany, the message from Fridays for Future has been received and understood. There is no serious political party, no responsible company today that has not recently made climate a priority, and there is no doubt the movement played a role in that sea change. Lack of awareness is no longer the problem.

Germany’s real problem, which stands in the way of real change, is deeper: the lack of trust in the power of human spirit and technology. This is precisely where the young must apply their next push — and where they require a push themselves.

Societies need morally rigorous young people, but they also need young people willing to take risks and reach for the impossible. Ms. Thunberg has urged the world to “panic.” But unchecked fear can itself be paralyzing, creating a rising generation convinced that action is pointless.

Pessimism afflicts more than just the young, of course. In April, researchers from the renowned Allensbach Institute published a devastating report showing that the percentage of Germans who believe in progress has reached a five-decade low. Asked if they thought that “humanity is headed toward a better future,” only 32 percent responded that yes, they believed in progress. A staggering 39 percent said that scientific research that carried even a minor risk for humans should be prohibited. This is amazing: If Germans discovered fire tomorrow, more than a third of us would rush to stomp out this frightening new source of heat and light. It might burn us!

There is more. Over the last two years, the number of annual startups in Germany has decreased by 100,000. Sarna Röser, the head of an association of young entrepreneurs, says her peers are having trouble finding German venture capital. “Germans are definitely becoming more risk-averse,” Ms. Röser told me.

If Germans of all ages are growing pessimistic, then it is all the more important that the youngest among us move beyond panic to provide constructive visions and solutions. Young Germans need to consider this: Do they want to live in a country that is bypassed by investors and loses track of technological advances in climate change? Or do they envision a Germany that uses its wealth and intellectual potential to become a front-runner in the efforts to take on climate change with whatever means human genius can produce?

The merits of the Fridays for Future movement will surely not be forgotten. Now it is time for everyone to get moving and get to work. Do not let your youth be wasted on your angst.

The young have the right, and the duty, to be morally rigorous.