A June Gallup poll found that 72% of Americans believe that our morals are “getting worse.” Similar majorities have complained about moral decay every year since Gallup began asking the question in 2002. Another recent poll by the Wall Street Journalconfirmed that a majority of Americans are worried about “moral decline.”

Moral declinism — to coin a phrase for the sense of moral decadence — has a long history. The ancient Jewish prophets warned of moral decay. The Greeks accused Socrates of corrupting the youth. Ancient Chinese philosophers imagined a lost era of true men and virtuous kings.

Change is often greeted with skepticism and nostalgia. We have a tendency to view the past through rose-colored glasses. We pine for the supposed simplicity of the family home. We are homesick for a mythical time when things were purer, easier and better.

Nostalgia is, however, a poor guide for morality. There is no perfect past this side of Eden. Indeed, many are happy to leave the past behind, especially when the past includes injustice and oppression.

Consider the demise of the Confederate flag. Some Southerners may be nostalgic for the antebellum South. But most Americans understand the rebel flag as a sign of an oppressive history and view its fall as a progressive development.

Or consider the gay marriage debate. Some, like the Rev. Franklin Graham, have described acceptance of homosexuality as a sign of “the moral decline we are seeing manifest daily around us.” But for homosexuals, these are times of moral progress.

The Supreme Court’s decision to legalize gay marriage explained that the institution of marriage “has evolved over time.” It argues that we must learn from history, “without allowing the past alone to rule the present.”

Opponents reject the idea that marriage can or should evolve. Chief Justice Roberts argued in his dissent that marriage “has formed the basis of human society for millennia.” Justice Alito added, in his dissent, that gay marriage is “contrary to long-established tradition.”

But tradition is not a sufficient guide to morality. The mere fact that something is old does not mean that it is good. Slavery is as old as the Bible. Its longevity is no justification.

The same point can be made with regard to new developments. New things are not better simply because of their novelty.

The key to moral progress is independent moral judgment based upon respect for human dignity. And the best method of making progress is dignified and rational critique. We reconstruct our values by trying to understand what matters and why.

Human beings are not perfectly wise, and human institutions are not perfectly just. We evaluate and improve things by criticizing them. Enlightened social progress results from reasonable civil discourse. Genuine moral progress must be grounded in good arguments that every citizen can understand.

Claims about a culture in decline are dangerous when they fuel the fires of social conflict. Indeed, some have warned about a newly emerging “culture war.” But the war metaphor is not helpful. Fundamentalists in some parts of the world take up arms to stifle dissent and preserve irrational traditions. Value conflicts can quickly escalate and become bloody.

We should reject the notion that Americans engage in culture wars. We argue and debate — and obey the rule of law, which allows us to agree to disagree. Moral argument is complicated and difficult. And some will be unhappy as change occurs. But in our system, social change happens without recourse to the blunt instruments of violence and war.

Instead of lamenting moral decline, let’s rejoice at the role of rational argumentation in American public life. Since the bloody civil war of the 1860s, moral development in the U.S. has happened in the courts, in Congress and through nonviolent civil disobedience. That’s moral progress.

We should, however, worry about a decline in civility and rational deliberation. Internet subcultures are filled with hateful speech — and terrible arguments. Some malicious morons turn hate speech into murder. Other citizens simply tune out. The solution to that problem is obvious. We have to teach our children to be more reasonable. And we should celebrate the fact that rational argument and civil discourse still guide our public life.