How did this happen?

The last 30 years or so have seen a kind of war on the very idea of visionary politics. Where ’60s rebels called for “all power to the imagination,” the consensus of the opinion makers who took over as those social movements sputtered has been precisely the opposite: The very idea of unleashing the human imagination on political life, we are consistently told, can lead only to economic misery, if not the gulag.

And as left and right both look to the past — the one toward midcentury welfare states and the other, darkly, toward xenophobia and nationalism — the collapsing center warns us to fear political passion of any sort. It’s all so much irrational “populism” — a term now used to tar anyone who objects that all key decisions affecting their lives should be made by technocrats trained in neoclassical economic theory. Yet the technocrats have so far proved utterly incapable of addressing the climate crisis.

If real passion and vision are necessary, they will have to come from outside the system. The activists who assembled and debated in London recognized that the goal of zero emissions in six years would require huge social and economic dislocation. But the very daunting nature of the task seemed to call out creative solutions.

These took many forms, from new mass transport systems to four- or even three-day work weeks, green industrial revolutions, spiritual awakenings and the replacement of the discipline of economics and its exhortations toward endless growth with a new science based on principles that rise to the challenges of a changing climate. Many of these ideas might seem ridiculous. Some no doubt are. But with scientists warning us we may have precious little time before rates of planetary warming lead to irreversible consequences, the one thing that seems clear is that refusal to engage in this kind of imaginative exercise is the real danger.

Threatened with irrelevance, some politicians have started to respond. In Britain, the opposition Labour Party under Jeremy Corbyn has now proposed that the first of Extinction Rebellion’s demands, a national state of climate emergency, be put to a vote in Parliament as early as Wednesday . Whether the motion is successful or not, it represents a previously difficult-to-imagine acknowledgment of the crisis.

It’s just barely possible that Britain, the nation that ushered in the Industrial Revolution and its explosive carbon emissions, might also be the first to make a serious effort to undo the damage.

But if the government can’t bring itself to do so, the people will have to. With any luck, they’ll be just in time to save the planet.

David Graeber is an anthropologist, political activist and the author of “Debt: The First 5,000 Years.”

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