But that very diversity means that the new reaction has appeal beyond anti-P.C. tweeters and Trumpist message boards. Reactionary ideas have made modest inroads in the mainstream right: The intellectuals’ case for Trump that I wrote about last week includes a thin but striking “regime change at home” thread. And they have appeal in areas like the tech industry where mainstream conservatism presently has little influence, because (like fascism in its heyday) the new reaction blends nostalgia with a hyper-modernism — monarchy in the service of transhumanism, doubts about human equality alongside dreams of space travel or A.I.

Then finally there is a third group of post-liberals, less prominent but still culturally significant: Religious dissenters. These are Western Christians, especially, who regard both liberal and neoconservative styles of Christian politics as failed experiments, doomed because they sought reconciliation with a liberal project whose professed tolerance stacks the deck in favor of materialism and unbelief. Some of these religious dissenters are seeking a tactical retreat from liberal modernity, a subcultural resilience in the style of Orthodox Jews or Mennonites or Mormons. But others are interested in going on offense. In my own church, part of the younger generation seems disillusioned with post-Vatican II Catholic politics, and is drawn instead either to a revived Catholic integralism or a “tradinista” Catholic socialism — both of which affirm the “social kingship” of Jesus Christ, a phrase that attacks the modern liberal order at the root.

Let me stress that these are very marginal groups. But like the radicals and neo-reactionaries they have an energy absent from the ideological mainstream. And all three post-liberal tendencies are in synch with aspects of the populisms roiling the West’s politics: the radicals with Bernie Sanders and Jeremy Corbyn and Podemos and Syriza, the neo-reactionaries with Trump and Brexit and Le Pen, the Catholic integralists with Eastern Europe’s rightward turn.

So their ideas are, perhaps, genuinely dangerous to the order we take for granted in the West. Or — it all depends — they might be beneficial, because liberal civilization’s flourishing has often depended on forces that a merely procedural order can’t generate, on radical and religious correctives to a flattened view of human life.

When those correctives are in short supply, the entire system becomes decadent. When they re-emerge, it’s best to learn from them — or else the next correction will be worse.