A doctrine that limited political power with laws and constitutional checks quickly became associated with rapid economic growth.

There was, moreover, a critical cognitive shift that took place in Europe around this time, which was the development of the scientific method. That method assumes that there is an objective world beyond our subjective consciousness, one that can be apprehended experimentally and ultimately manipulated to serve human purposes. It was this technique that produced continuous technological change and allowed the modern economic world to emerge.

These ideas were all part of a doctrine that came to be known as liberalism, in which political power would be limited by law and constitutional checks on the ruler's authority. It quickly became associated with the rapid economic growth that took place in early liberal societies like England and the Netherlands. The scale of markets and efficiency of production increased many fold, aided by technological developments like seaborne transport and long-range navigation. With the direct application of the scientific method to the development of technology, the industrial revolution was born at the turn of the 19th century, producing the steady economic growth that has characterized the world economy ever since.

Modernization is a coherent process involving capital accumulation, investment and increasing economies of scale. It produces similar social results regardless of the cultural starting points of the society in which it occurs. Agrarian societies see peasants leaving the countryside for cities or sometimes being forcibly driven off the land. Cities grow in size and importance, and levels of education begin to rise as requirements for literacy and an increasing range of skill expands. Social classes emerge: One group owns capital, another works for them, and in between there emerges a middle class of professionals, merchants, middlemen and those who provide services for an increasingly complex society.

The 19th-century German social theorist Ferdinand Tönnies described this transition as one from Gemeinschaft (community) to Gesellschaft (society)--from the small, isolated village community to the diverse, urban industrial city. This process unfolded in Western Europe and North America beginning in the late 19th century and took place in Asian societies like Japan, South Korea and China in the 20th century.

So there is an arc of history. The second question is where is it pointing, and in particular, whether it is pointing toward "justice." When President Obama used the phrase, he was doubtless thinking about justice in two senses: first, a high degree of social and political equality; and second, a political system that protects the autonomy of each individual, that is, a person's ability to pursue a flourishing life as they see fit, free from violence, war or coercion.

In earlier historical periods, the arc of history bent away from justice. Tribal societies are relatively egalitarian: They disperse power and often operate by consensus. It was only with the development of the state that dictatorship and slavery could exist on a large scale. Many historians have pointed as well to the deterioration of human health and well-being that occurred as diets shifted to grains and peasants were forced into stationary and rigidly limited lives.

Regimes committed to principles of equality and freedom have doubtless spread substantially over recent centuries. But what if the arc of history is pointing elsewhere--toward, perhaps, a Chinese-style hi-tech authoritarianism or to a nationalist illiberal democracy like Viktor Orban's Hungary? Liberal democracy has not triumphed universally around the world and, indeed, has been in retreat over the last 15 years. This retreat is marked not just by the rise of authoritarian great powers like Russia and China but also by democratic backsliding in established democracies like India and the U.S.

The liberal narrative of historical progress was closely tied to the belief that people were rational and that better education and access to information would make them more critical of unjust authority and open to diverse ideas. This scenario is not playing out in today's China, where an increasingly well-educated population seems to be content living under a dictatorship. Nor did this narrative anticipate the impact of technology, which has allowed governments to control information in novel ways and malign actors to weaponize it in ways that undermine democratic self-confidence.

In order to see that there has been progress toward justice, it is important to recognize that History is not a linear process in which we make slow but steady improvements every year. Rather, it is marked by huge discontinuities, with periods of peace and spreading freedom interrupted by giant wars and setbacks. One needs to step back and take a long-term perspective. While it may seem counterintuitive at a moment when Europe is consumed by a war between major powers, a number of scholars such as Steven Pinker have shown that aggregate levels of violence have fallen dramatically over the millennia as human societies have evolved from hunting and gathering.

The liberal idea remains very vivid for the hundreds of thousands of people who leave poor and violent countries each year in search of freedom and opportunity.

A century ago, the greater part of the earth's landmass was held in colonial domination by a handful of Western powers. Since then, the idea that each society should be sovereign and free to govern itself has taken hold everywhere. What makes Mr. Putin's invasion of Ukraine so shocking is that he seems to be still living in that 19th century colonial world, unwilling to recognize the grassroots power of ordinary people like the Ukrainians resisting him.

The great French observer of American democracy Alexis de Tocqueville noted that the idea of human equality had been spreading inexorably for centuries prior to his visit to America in the 1830s. He related the story of Madame de Sévigné, the educated and aristocratic patroness of a Paris salon in the 17th century, who wrote a lighthearted letter to her daughter noting she had witnessed a tailor being broken on the wheel for stealing a loaf of bread. Tocqueville comments that her amusement at this scene reflected the fact that she simply could not see the tailor as a fellow human being. Such a lack of empathy, he writes, would be impossible in his own age, which had been shaped by the egalitarian ideals of the French Revolution.

We can all point to contemporary instances in which immigrants, refugees or members of racial and sexual minorities are similarly dehumanized and excluded from our circle of human solidarity. But with every passing generation, it has become harder to do this. Virtually no regime today bases itself on an assertion of overt social hierarchy or denies the principle of democratic legitimacy, even if disregarding it in practice. Modern technology has been weaponized, but it has also made the suffering of distant peoples vivid to us in ways that were previously impossible. Witness the upsurge in sympathy for the suffering of Ukrainians that has swept over Europe and North America since the beginning of the Russian invasion.

From a long-term perspective, liberalism has seen its ups and downs but has always come back in the end.