One of the most subtle critics of the Left on this point was Patrick Deneen in his early book Democratic Faith. Deneen and other postliberals are now best known for taking broad swipes at liberalism that often miss their mark. But in contrast to his more recent and more polemical work, Democratic Faith is a patient, careful look at the history of political thought and the overambitious aspirations sometimes ascribed to the push for greater democracy and equality. He even describes it as a “friendly” critique of broadly progressive positions.

Deneen charges that modern progressives abandoned antiquarian wisdom that acknowledged the fallen and imperfectible nature of human beings. Echoing Sowell, where classical writers like St Augustine attributed social failings to human nature, the essence of modern “democratic faith” was to attributes flaws in human nature to social failings. This opens the door to claiming that if only we get the right social institutions and practices in place, human beings can be perfected.

Deneen acknowledges that philosophers like Jean-Jacques Rousseau and John Dewey weren’t thoughtlessly starry-eyed about the future. They were often keen to point out the many ways in which human beings fell well short of the ideal in their dealings with one another and could even display keen psychological insight into the nature of human desire, resentment, and envy. But where conservatives tended to accept these as immutable constants that had to be managed afresh every generation, progressives believed that progress was possible. For thoughtful leftists, this would not just be material or institutional but also transformative moral progress. Education, fairer institutions, and the tutelage provided by democratic life would gradually make human beings better than they were. This was an article of faith for Deneen, since the aspiration for greater human perfection always had to be projected into an unknowable future.

Deneen contrasted the optimism of this perfectionist faith with those who “view our condition as partial, frail, incomplete and insufficient creatures” and so were wary of the belief in advancement. Deneen suggested to defenders of equality that acceptance of our permanently fallen nature might still be a “democratic ethic, given its derivation as a recognition of human partiality and frailty.” It could even be a “strongly egalitarian ethic — particularly with its stress on our common insufficiency,” but it would resist the egalitarian claims of those who imagined a future equality of brotherhood shorn of human vulgarity and the temptations to do evil.

Deneen is undeniably right that some have attributed unrealistic hopes to what socialist change might be able to achieve. Occasionally, left-wing thinkers have anticipated massive improvements in our intellectual and moral being that no social system could bring about on its own. An emblematic example is Leon Trotsky’s 1924 ruminations on the communist man of the future. Responding to the Nietzschean fear that communism would lead to a mass leveling to the herd type, Trotsky famously projected vast hopes about the human potential that communism would unleash:

The shell in which the cultural construction and self-education of Communist man will be enclosed, will develop all the vital elements of contemporary art to the highest point. Man will become immeasurably stronger, wiser and subtler; his body will become more harmonized, his movements more rhythmic, his voice more musical. . . .  The average human type will rise to the heights of an Aristotle, a Goethe, or a Marx. And above this ridge new peaks will rise.

Trotsky hypothesized that socialist man would be aesthetically and intellectually perfected. But plenty have also mused that it might be possible to morally perfect people. A good example of the latter tendency can be seen in Vanessa Christina Wills’s recent book, Marx’s Ethical Vision. Wills reads Karl Marx as (potentially) predicting that morality itself would be abolished in a “fully developed communist society.” This is because human beings would have so completely internalized prosocial attitudes that any and all bad behavior would simply be off the table. Human beings in a fully developed communist society “would be no more morally required to behave in prosocial ways than they are ‘morally required’ to be primates,” she writes.

I disagree with Wills’s reading of Marx on this point, but it reflects a thoughtful spin on Trotskyite optimism. On this view, in the era of communism, morality will wither away like the state. Human beings will become so prosocial that there will be no more need for explicit morals; we will do the right thing not because it’s the right thing but because we would never be inclined to do otherwise.

Conservative critics are right that some on the Left have indulged in excessive hopes about the intellectual and, above all, moral improvements socialism would effect in ordinary people. But their arguments are exaggerated in suggesting all or even most socialists are excessively naive about human nature. In fact, one of the best arguments for socialism is precisely that, by breaking down concentrations of power and protecting the vulnerable against domination and exploitation, it could do a better job of guarding against humanity’s enduring flaws. It does this at the same time as it makes greater ethical demands of social institutions, even while recognizing that individuals will often fall short of them.

The theologian Reinhold Niebuhr’s thought offers insights on this score. Beginning as a radical Marxist, Niebuhr later gravitated toward more mainstream liberalism before becoming increasingly critical of American foreign policy. During his socialist period, he published a classic book, The Children of Light and the Children of Darkness, that made a deep case for left-wing optimism of the will and pessimism of the intellect. It was written at the peak of World War II, after Niebuhr and his comrades had just witnessed the darkest barbarities human beings were capable of.

He recognized that to counteract such barbarism, a realist about human nature had to be something of a radical in politics. After all, pro-capitalist liberals and conservatives had overseen the Depression and the fall into fascism. Among other reforms, guarding against the evils human beings were capable of would require challenging private property and private ownership of the means of production. Niebuhr was scathingly critical of the “prevailing presupposition of liberal thought that property represents primarily an ordinate and defensive power to be used against the inclination of others to take advantage of the self.” The reality was that “property, as every other form of power, cannot be limited to the defensive purpose. If it grows strong enough it becomes an instrument of aggression and usurpation.” In this respect, “Marxism is nearer the truth than liberalism on the property issue” in having a clearer understanding of the dangers private ownership of the means of production poses to everyone — even if Marxists were sometimes too rosy-eyed in assuming socialization of property could get rid of predatory behavior once and for all.

In an era that has crowned the world’s first trillionaire, Niebuhr’s analysis resonates more than ever. One of the merits of liberal theory has been recognizing that power corrupts, and that absolute power corrupts absolutely. For these reasons, liberals have always understood that concentrations of power are dangerous, and so power ought to be dispersed as widely as possible. But with the exception of liberal socialists, most liberals have at best been cautious in applying this reasoning to the economy.

This is a very serious mistake, since it’s in the economic sphere where we mostly clearly see how concentrations of wealth lead to concentrations of power — and, from there, to the most corrupt and domineering behaviors human beings are capable of. In The Children of Light and the Children of Darkness, Niebuhr claimed that man’s “capacity for justice makes democracy possible, but man’s inclination to injustice makes democracy necessary.” It is long past time that liberals acknowledge the socialist insight that the human inclination to injustice makes economic democracy as necessary as political democracy.

In this respect, in a liberal and democratic socialist society, people would be safer than they are under capitalism and the vulgarities of human nature would be better offset. But I also think socialism would be a more ethical society than alternatives, though not in a way that is unrealistic or perfectionist.

In his recent book, Cosmic Connections, the Catholic philosopher Charles Taylor defends egalitarianism by stressing that it is more ethically demanding than conservative and hierarchical views. The latter narrow our range of ethical obligations, by insinuating that certain privileged groups are entitled to special concern that others are not. Many of the antiquarian thinkers Sowell and Deneen love to reference would have no qualms about insisting that the Athenian people can put Athens first, even if that meant enslaving the people of Milos. By contrast, modern ethics demands we treat every human being as a moral equal — a view so demanding we’ve yet to establish societies that fully realize it. But Taylor isn’t naive in thinking that just because egalitarianism is a more demanding ethic that we have, or even will become, better people. Instead, he thinks our ethical standards — for instance, those espoused in the Universal Declaration of Human Rights — are higher than those of antiquity and America First populists. Taylor credits egalitarian institutions with trying, however imperfectly, to live up to these ambitious universal and egalitarian principles.

Socialism would do a better job of trying to institute respect for these principles through the extension of democracy into the economic sphere, thereby eliminating certain temptations to domination. That won’t necessarily lead most people to become better versions of themselves. Democratic socialism can’t keep your spouse from cheating on you with your best friend. But it can make sure that when the divorce proceedings happen, you aren’t dead broke, and that your children won’t see their own life chances damaged because of the resulting financial strain. Nor is democratic socialism going to turn your selfish next-door neighbor into a good Samaritan. But it would create a system where her taxes help pay for quality health care when you get sick.

One of democratic socialism’s merits would be realizing high standards of justice while not demanding moral perfection, or even great virtue, from ordinary citizens. I suspect that, over time, a more solidaristic ethos would emerge, and that most citizens would find the greater sense of community edifying. But the system would function regardless. In this sense, a feasible socialism would answer Deneen’s calls for an egalitarian ethic that acknowledges our flawed nature.

Today it is not the Left that is naive about the world. There is mounting evidence that existing institutions are facing a crisis of legitimacy, with ordinary people growing ever more disdainful of the status quo’s oligarchic concentrations of wealth and power. Yet center-right and conservative commentators continue to insist that it is naive to demand better health care and wages for all. The real naivete is the idea that things must continue as they are.