Joe Biden built his 2020 presidential campaign around the idea that “we’re in a battle for the soul of America.” I thought it was a marvelous slogan because it captured the idea that we’re in the middle of a moral struggle over who we are as a nation. In the video he released this week launching his re-election bid, he doubled down on that idea: We’re still, he said, “in a battle for the soul of America.”

I want to dwell on the little word “soul” in that sentence because I think it illuminates what the 2024 presidential election is all about.

What is a soul? Well, religious people have one answer to that question. But Biden is not using the word in a religious sense, but in a secular one. He is saying that people and nations have a moral essence, a soul.

Whether you believe in God or don’t believe in God is not my department. But I do ask you to believe that every person you meet has this moral essence, this quality of soul.

Because humans have souls, each one is of infinite value and dignity. Because humans have souls, each one is equal to all the others. We are not equal in physical strength or I.Q. or net worth, but we are radically equal at the level of who we essentially are.

The soul is the name we can give to that part of our consciousness where moral life takes place. The soul is the place our moral sentiments flow from, the emotions that make us feel admiration at the sight of generosity and disgust at the sight of cruelty.

It is the place where our moral yearnings come from, too. Most people yearn to lead good lives. When they act with a spirit of cooperation, their souls sing and they are happy. On the other hand, when they feel their lives have no moral purpose, they experience a sickness of the soul — a sense of lostness, pain and self-contempt.

Because we have souls, we are morally responsible for what we do. Hawks and cobras are not morally responsible for their actions; but humans, possessors of souls, are caught in a moral drama, either doing good or doing ill.

Political campaigns are not usually contests over the status of the soul. But Donald Trump, and Trumpism generally, is the embodiment of an ethos that covers up the soul. Or to be more precise, each is an ethos that deadens the soul under the reign of the ego.

Trump, and Trumpism generally, represents a kind of nihilism that you might call amoral realism. This ethos is built around the idea that we live in a dog-eat-dog world. The strong do what they can and the weak suffer what they must. Might makes right. I’m justified in grabbing all that I can because if I don’t, the other guy will. People are selfish; deal with it.

This ethos — which is central to not only Trump’s approach to life, but also Vladimir Putin’s and Xi Jinping’s — gives people a permission slip to be selfish. In an amoral world, cruelty, dishonesty, vainglory and arrogance are valorized as survival skills.

People who live according to the code of amoral realism tear through codes and customs that have built over the centuries to nurture goodness and foster cooperation. Putin is not restrained by notions of human rights. Trump is not restrained by the normal codes of honesty.

In the mind of an amoral realist, life is not a moral drama; it’s a competition for power and gain, red in tooth and claw. Other people are not possessors of souls, of infinite dignity and worth; they are objects to be utilized.

Biden talks a lot about the struggle between democracy and authoritarianism. At its deepest level, that struggle is between systems that put the dignity of individual souls at the center and systems that operate by the logic of dominance and submission.

You may disagree with Biden on many issues. You may think he is too old. But that’s not the primary issue in this election. The presidency, as Franklin D. Roosevelt put it, “is pre-eminently a place of moral leadership.”

One of the hardest, soul-wearying parts of living through the Trump presidency was that we had to endure a steady downpour of lies, transgressions and demoralizing behavior. We were all corroded by it. That era was a reminder that the soul of a person and the soul of a nation are always in flux, every day moving a bit in the direction of elevation or a bit in the direction of degradation.

A return to that ethos would bring about a social and moral disintegration that is hard to contemplate. Say what you will about Biden, but he has generally put human dignity at the center of his political vision. He treats people with charity and respect.

The contest between Biden and Trumpism is less Democrat versus Republican or liberal versus conservative than it is between an essentially moral vision and an essentially amoral one, a contest between decency and its opposite.