The Reductio ad Hitlerum fallacy is a fixture of online political debates. It’s used often by secular progressives, who seem to view disagreements with their policy preferences as evidence of Nazi sympathies. The tendency is so common that it has prompted a satirical description known as “Godwin’s Law,” which predicts that as any two people argue on the Internet, the probability that one will compare the other with a certain German dictator approaches 100%.

That the onetime chancellor’s name comes up so often says a lot about people’s moral imaginations—and their deepest fears. As British popular historian Tom Holland points out, Westerners no longer talk of Satan and devils, but about Hitler and the Nazis. Our demonology has shrunk so that the worst villains we can imagine are flesh-and-blood characters from the drama of the 20th century—bad hombres to be sure, but hardly the Father of Lies.

If you ask me, this rush to condemn opponents in the most hysterical terms possible betrays a gnawing fear—a fear that maybe Nazis could win the debate if they were ever given a platform. And this may be why so many left-wing college students are ready to cancel, censor, or punch anyone who questions the ever-lengthening list of “human rights” and protected classes. In their thinking, none of us is ever more than one microaggression away from becoming a monster. They double down on the name-calling because they fear that those who fall out of progressive lockstep will inevitably start to goosestep.

Holland seems to agree. He suggests that one reason secular progressives are paranoid about resurgent Nazism is that they have no foundation for their vast and growing edifice of “fundamental human rights.” In a recent panel discussion, he repeated a claim he makes in his book, Dominion: that human rights and dignity are anything but universal or self-evident and that the only reason Westerners are still convinced such things exist is that we have a Christian hangover:

“Because the West has been hegemonic for so long,” he says, “it’s in a position to assume that its concept of human rights is universal. [Westerners] don’t need to think about it. Of course human rights exist! But what the rise of China and the rise of other civilizational powers is doing is to remind us that the concept of human rights…emerged in a very specific cultural matrix, which is a Christian one. And that therefore, if you want to believe in human rights, you have to believe. It takes a leap of faith to believe that there are things called human rights just as much as it takes a leap of faith to believe that Jesus Christ raised from the dead. They’re both beliefs.”

And herein lies the problem for secular progressives, whose worldview dispenses with the Christian God and His commands. If the basis for human rights is not faith in divine law, then what is it? This problem worsens when we recall that secularism banished God with a materialist account of human origins: Darwinian evolution. But this theory is a double-edged sword. It may drive God from our moral universe, but it drives out human rights with Him. After all, if fierce competition between rival populations leads to the origin and improvement of species, as Darwinism holds, then there is no good reason this process should not continue in our own species. Or will we condemn the very process that created us? If the law of nature is “survival of the fittest” and death to the weak and diseased, then universal rights are not only ethical nonsense—they’re biological suicide.

None of this was lost on the Nazis. As Dr. Richard Weikart explained this week on Upstream, the real-life Third Reich found Darwinian evolution to be an invaluable tool in advancing its program of racial extermination. Actually, his argument is bolder. In his book, Darwinian Racism, he documents how Darwinian concepts and language were woven into every aspect of Nazi ideology, from its science and curricula to its propaganda and military objectives. Key Nazi figures all the way up to Hitler himself were convinced that their project was a natural outworking of Darwinian principles—indeed, that the reassertion of Aryan racial identity was a way of accelerating humanity’s evolution. Likewise, the Nazis saw the notion of universal human rights as both absurd and a means by which unfit groups parasitize the worthy and strong.

Secular progressives—most of whom still cite Darwinian evolution with dogmatic enthusiasm—will find Weikart’s arguments infuriating. Much ink has been spilled in the attempt to distance Darwinism from Nazism and to avoid the conclusions Nazis drew from it. Dr. Weikart has participated in that debate for decades, and he devotes a large portion of this latest book to answering such objections. I found the evidence he marshals convincing, and I suspect you will, too. But that’s not my focus right now.

I don’t think the theory of evolution is false simply because Nazis were evolutionists. The point I am making is that secular progressives who treat Nazism as the ultimate evil have no moral basis for condemning what the Nazis thought or did. Human rights require human beings to be much more than animals. No other creature on earth has ever imagined that killing its prey or its competition might be immoral. Yet we seem unable to shake the conviction.

What if secular progressives are so quick to invoke Hitler because they sense their own worldview’s vulnerability to his ideas? What if they rightly believe that exterminating people on the basis of race is evil, but can’t back it up with moral reasoning? What if they know on some level that human rights endowed by no one are a house of cards, but we are already too invested in the game to quit? What if Godwin’s Law is all you have when you want law without God?

These are questions anyone who looks seriously at the 20th century must ask, especially if that person has already jettisoned the traditional foundation for human dignity in the will of God and His image in man. What is to keep those horrors permanently at bay with the wind of Darwinian logic still in their sails, and no anchor in human exceptionalism to hold them back? Certainly not secular pretensions about self-evident rights. We can repeat that line all we like, and sic the ghost of Hitler on all who question us. But as King Saul learned the hard way, those who call up the dead should be ready for the dead to call their bluff.