The belief systems that used to reinforce a faith in progress have become less influential. First there was moderate religiosity, the belief that God is ultimately in control, that all things are ultimately fashioned toward the good and that the arc of history bends toward justice. This was the mind-set that made Martin Luther King Jr. fundamentally optimistic, even in temporarily dark times. Then there was humanism, the belief that people are learning more and more, inventing more and more, and so history is a steady accumulation of good things.

As humanism and moderate religion have withered, gloom has pervaded that national mind. It doesn’t matter how much living standards rise or the poverty rate falls, it makes you seem smart and woke to be alarmed and hypercritical. Every dour attention-grabber wants to claim that the elites are more corrupt than ever.

The paranoid style of conspiracy-mongering has become the lingua franca of the internet. Public conversation is dominated by people’s ahistorical insistence that this country is sliding toward decline. As Arthur Herman writes in his book “The Idea of Decline in Western History,” “The sowing of despair and self-doubt has become so pervasive that we accept it as a normal intellectual stance — even when it is directly contradicted by our own reality.”