Three years after World War II ended, the United Nations affirmed that “everyone has the right to freedom of thought, conscience and religion.” The UN did so in Article 18 of the Universal Declaration of Human Rights, which the world body adopted on Dec. 10, 1948.

Despite the UN’s stand for religious liberty, 60 years later about a third of all nations severely restrict religion. And, according to the Pew Forum on Religion & Public Life, about 70 percent of the world’s population lives in these countries.

In some cases, totalitarian regimes oppress religious individuals and groups generally. In others, statist regimes built on an established religion persecute minority faiths.

These governments lack what we take for granted in the United States: a constitutional framework that values religion and protects religious liberty. The key to America’s success story on religious liberty is in the Founders’ design. The Constitution protects the free exercise of religion while prohibiting the establishment of a national religion.

The Founders frequently stated that a free society could not survive without virtue and religion. They knew that family, congregations and other private associations exercise moral authority that is essential to limiting the size and power of government.

This constitutional order produced a constructive relationship between religion and state. It balances citizens' dual allegiances to God and earthly authorities without forcing believers to abandon or moderate their primary loyalty to God. This habit of reconciling civil and religious authorities, as well as the process of harmonizing the interests of competing religious groups, was instrumental in developing self-government.

The lesson remains applicable today as American foreign policy seeks to promote freedom in highly religious societies abroad. Our ability to do that, however, is hampered by our poor understanding right here at home of the religious roots of the American order and religion’s role in its continued success.

One source of the confusion is the phrase “separation of church and state.” It appears not in the Constitution but in a letter President Thomas Jefferson wrote in 1802 to the Danbury Baptist Association of Connecticut.

Many Americans think it refers to a radical separation of religion and politics. Some have suggested that religion should be entirely personal and private, kept out of public life and institutions such as public schools. But that’s not what Jefferson had in mind.

The American model of religious liberty takes a strongly positive view of religious practice, both private and public. In fact, the Founders considered religious engagement in shaping the public morality essential to ordered liberty and the success of their experiment in self-government.

More recently, American leaders also recognized that religious freedom abroad serves U.S. national interests.

In 1998, Congress committed to promote freedom of religion as “a fundamental human right and as a source of stability for all countries.” The lawmakers passed a bill requiring the State Department to report annually on religious liberty around the globe. The agency was required to identify “countries of particular concern” that severely restrict religious freedom.

Nations that earn the ignominious “CPC” label—North Korea, Iran and Burma among them—also tend to offer their people the least economic liberty and some of the worst economic conditions, as shown in the Index of Economic Freedom co-published by The Heritage Foundation and The Wall Street Journal.

On the other hand, governments that respect religious liberty tend to respect other freedoms as well. Religious freedom is strongly related to political liberty, economic freedom and prosperity. As researcher Brian Grim notes, “[W]herever religious freedom is high, there tends to be fewer incidents of armed conflict, better health outcomes, higher levels of earned income, and better educational opportunities for women.”

Some academics used to predict that political and social progress eventually would marginalize religion. But religious belief and practice remain widespread and active around the world, as British journalists John Mickelthwait and Adrian Wooldridge documented in their 2009 book “God Is Back.”

“The very things that were supposed to destroy religion—democracy and markets, technology and reason—are combining to make it stronger,” Mickelthwait and Wooldridge write.

Religion’s persistence shouldn’t be surprising. God has been on the minds of mankind in every generation. That’s not about to change—as long as conscience, the mystery of existence and the prospect of death challenge every human being to grapple with questions of transcendence and divine reality.

Earthly governments should acknowledge and constitutionally protect the right to pursue those ultimate questions.

Jennifer A. Marshall is director of the DeVos Center for Religion and Civil Society at The Heritage Foundation (heritage.org) and author of “Now and Not Yet: Making Sense of Single Life in the Twenty-First Century.”