In daily personal market transactions, the dynamics of mutual gain were once readily apparent. A buyer of meat from a butcher could readily see that he valued the meat more than the money he paid for it. The seller earned his living from the transaction. Each could recognize the other as a partner in mutual advantage.

　　Contrast this process with politics, even democratic politics. There, the mutual gains are not nearly as visible or immediate, even when they arise from the creation of public goods such as scientific research and national defense. Moreover, because political decisions bind even those who oppose them, politics can more easily appear exploitative, and since an individual is not responsible for, and is rarely knowledgeable about, the decisions made on his or her behalf, conspiracy theories find fertile ground.

　　Today, Americans are losing the habits that once made mutual gain visible. Small-scale markets, associations, churches, and local government teach that another person’s success can improve others chances of success. When those institutions weaken, politics supplies enemies to fill the void.

　　The progressive version declares that the billionaire’s fortune, the corporation’s profit, and the landlord’s rent must have been extracted from ordinary people. The populist-right version declares that the immigrant’s job and the foreign producer’s sale must have come at the American citizen’s expense. The targets differ, but the underlying sentiment is the same: Someone else’s gain is our loss.

　　One must carefully distinguish zero-sum politics from more legitimate political issues. Mass immigration does have costs in cultural disruption. Foreign trade can threaten industries essential to national security. Monopolies can gain rents rather than provide welfare for consumers. Redistribution may be necessary to meet the needs of those who cannot easily provide for themselves. By zero-sum politics, I do not mean the recognition that some policies create winners and losers—any serious politics must acknowledge tradeoffs. I mean the habit of treating another group’s gain as presumptive evidence of one’s own dispossession.

　　Much of our politics abandons these substantive debates and instead demonizes groups whose activities often create gains for society. On the left, the mayor of the city with the most billionaires in the world has said that billionaires should not exist. His rent policies treat landlords, including many small landlords, less as suppliers of housing than as obstacles to affordability. The populist left’s list of villains keeps expanding: franchisors, CEOs, landlords, and tech entrepreneurs. Of course, the government has a role in combating monopoly and fraud. But a unifying idea among much of the left is to treat the magnitude of wealth as evidence that it was taken from the rest of us, even though in reality, entrepreneurs capture only a small percentage of the consumer welfare they generate.

　　On the right, opposition even to legal, high-skilled immigration often rests on the false belief that immigrant workers simply take American jobs, rather than also creating jobs and increasing productivity. Similarly, opponents of foreign trade focus on what foreigners receive, to the exclusion of what American consumers benefit. They wrongly see free trade deals as selling out Americans rather than benefiting both Americans and their foreign counterparts.

　　What explains the rise of this zero-sum politics? Economic insecurity may be part of the story, but it cannot be the whole one. Trade and technological change create aggregate gains while imposing concentrated losses, and those losses can be politically explosive. The China shock, for example, may help explain some of the geography of populist discontent. But economic loss alone cannot explain why both the left and the right increasingly interpret the gains of outsiders, including immigrants, billionaires, foreign producers, landlords, and corporations, as moral injuries. While some have lost out, the median income of Americans continues to grow. Something deeper has happened to the institutions that once taught Americans to see mutual advantage.

　　The utility of the butcher, brewer, and baker was once readily recognizable. In contrast, the modern consumer benefits from a supermarket without seeing the strangers whose efforts made the benefit possible. The gain remains real, but the giver is no longer as visible.

　　We can push back against the politics of rage and envy by remembering the mutual gain logic of the marketplace.

　　Civic associations are also small schools of mutual gain. In a church or neighborhood association, people contribute different talents and resources to produce something that no one could easily produce alone. They learn that cooperation with people unlike themselves is not a concession but a source of strength. But as documented by Robert Putnam in Bowling Alone, America has suffered a decline in such communal engagement. He observed that “for the first two-thirds of the twentieth century a powerful tide bore Americans into ever deeper engagement in the life of their communities, but a few decades ago—silently, without warning—that tide reversed, and we were overtaken by a treacherous rip current.” The training in positive-sum cooperation has become much weaker.

　　Mutual gain thinking is not natural to a society of strangers. It must be reinforced by learning in the market and civil society, particularly in our more complex society. It is learned through repeated cooperation with people who have different talents, resources, and interests. It is learned when citizens see that another persons success can enlarge rather than diminish the field of opportunity. A society that loses these small schools of mutuality will be more tempted by a politics of enemies.

　　Another change has been the rise of political polarization. The Democratic and Republican parties have become more ideologically homogeneous and moved toward extremes. This polarization is sometimes thought to be caused by social media, but that ugliness is more a symptom than a cause. The roots of these divisions go deep.

　　First, political parties are now largely populated by those with a strong ideological interest in politics. For most of American history, political clubs were much more broadly based. There were few other uses for social time, so people naturally gravitated toward political activity. But now that there are hundreds of cable television channels and scores of different avocations within affordable reach, parties attract the hardcore ideologues. They filter out moderates.

　　Second, the success of Western economies has changed the nature of politics. As societies become wealthier, politics moves from material questions to questions of status and identity. These issues are harder to reach compromises about because the differences are less easily split.

　　Polarization then undermines the sense of mutuality of gains. Ordinary disagreement is compatible with a sense of mutual gains. But polarization makes one more likely to believe that one’s opponent is not just mistaken but a threat.

　　Polarization also narrows the civic imagination. It teaches citizens to care first about the in-group and to distrust gains flowing to out-groups. Shanto Iyengar and Masha Krupenkin describe contemporary party polarization as increasingly affective rather than merely ideological. They argue that partisans come to see opponents as a stigmatized out-group. That out-group psychology is hostile to the very idea of diffuse mutual benefit. It asks not, “does this enlarge the whole?” but “which side benefits?”

　　Positive-sum policy is often complicated. It requires explaining unseen benefits. An enemy is simple. The rich stole your future. China stole your job. Immigrants took your wages. Landlords caused your rent increase. Corporations caused inflation. Thus, polarized politics does not merely reflect zero-sum thinking. Instead, it manufactures that thinking.

　　It is not a surprise, even if disappointing, that academic troubadours of the zero-sum society are enamored of Carl Schmitt, the political theorist who made the distinction between friend and enemy foundational to politics. Despite his beginnings as the court philosopher of the early Nazi regime, professors on the extreme have embraced him. His renewed popularity is proof of our political peril.

　　Given the deep social and technological forces pushing us toward more zero-sum political thinking, it is not easy to produce solutions. There is certainly no single silver bullet. But a few social reforms are promising.

　　First, restore visible market reciprocity by removing the obstacles to small businesses. The reforms would include occupational licensing reform, easier rules for small businesses, and less zoning hostility toward small commercial uses.

　　Second, reduce the incentives for enemy-focused politics. For instance, the top two primaries, in which candidates of all parties run in the same primary with a run-off in the general election, may make it harder for extremists to be elected. In that system, an extremist can be more easily defeated by a moderate candidate of his own party who can draw support from members of the other party in both the primary and the general election. This helps temper political polarization.

　　Third, lower the political stakes. Decentralizing issues through federalism also lowers the stakes because people can move to a more congenial state. Reducing the power of the administrative state encourages deliberation and compromise in Congress and prevents any single president from imposing an extreme policy agenda.

　　Of course, these reforms face a chicken-and-egg problem. They require some confidence in mutual gain even as they try to restore it. But associations, churches, schools, and more local governments can help create the habits of mind conducive to accepting mutual gain. When they weaken, politics supplies enemies in place of partners. Our task is to make mutual gain visible again.