WASHINGTON (RNS) Do religious individuals and groups possess a right to share their beliefs with others in the hope that those beliefs will be embraced? Do religious groups have a right to defend their respective identities against efforts to convert their adherents?

For many — including most Muslims and Christians — religion represents an objective and universal truth, one that comprehends the temporal good and the eternal destiny of all persons. For those who believe they have access to such a truth, the desire to offer it to others is both natural and rational.

On the other hand, proselytism has sometimes been socially disruptive and even rapacious, undermining the structures of families and communities.

Is there a way to balance the right to persuade by peaceful witness with the right of communities to defend their respective identities? If there is a legal “right” to pursue one or both of these activities, what are the limits? Can the law legitimately ban foreign missionaries? Can it punish apostates?

The way these and related questions are addressed and answered will have enormous implications for American interests, justice, and world peace in the 21st century.

Christianity and Islam each have a theological imperative to convert others. Their respective historical expressions of proselytism have varied widely. Early Christians spread the faith peacefully while suffering grave persecution; later Christian rulers such as Charlemagne sometimes employed coercion to command the adoption of Christianity. Early Muslim armies spread the rule of Islam through military conquest; yet many Muslims embraced Islam voluntarily.

Both Islam and Christianity have been quite successful in their conversion activities, and the effects on history and international affairs have been momentous.

Yet the two religions have sometimes clashed. The crusades, for example, were a failed attempt by Christian Europe to retrieve lands lost to Muslim conquest. During the 20th century, adherents of the two religions managed to live in relative harmony in most Western nations, including the United States. But the 9/11 terrorist attacks, and the ensuing U.S. response, have heightened awareness of historic divisions, even as Muslim and Christian leaders have worked to overcome them.

During the 21st century, Muslim and Christian proselytism will affect U.S. interests around the globe, especially in the greater Middle East. Large numbers of Muslims, it seems, believe American foreign policy is designed to undermine Islam by, among other things, supporting Christian missionaries. By the same token, many Americans and others in the West believe Islamist extremism and the activity of jihad are violent expressions of Islamic proselytism.

How, then, are we to think about proselytism?

Should it be condemned and banned as a cause of conflict? That seems unlikely. The right to convert is generally understood as a central element of the right to religious freedom. The American idea of religious liberty has historically centered on the rights of free persons to change their religious beliefs and to persuade others to change as well. In the Universal Declaration of Human Rights, the right to publicly “manifest” one’s religious beliefs is companion to the “freedom to change” those beliefs.

The reality is, however, that proselytism remains highly controversial.

Historically, it has sometimes been violent and mercenary. It has exploited ignorance, poverty and emotional loneliness, and harmed longstanding communities of faith. In states with dominant religious traditions, the arrival of foreign missionaries has sometimes triggered severe reactions. In some, domestic theological interpretations have yielded laws rejecting proselytism. In Saudi Arabia, Sudan and Yemen, for example, conversion by a Muslim to another religion is punishable by death — both for the apostate and the proselytizer.

By the same token, there is historical and contemporary evidence that proselytism has also had positive effects, such as the spread of literacy (including female literacy) and human rights.

If proselytism is understood as peaceful persuasion, respectful of human dignity, culture and tradition, evidence suggests it can contribute to stable, liberal and just governance. Social science data suggest that religious conversions — usually the result of some form of proselytism — are associated with more open societies, and therefore with more democratic and successful societies.

On balance, it seems reasonable to conclude that both religion and democracy can benefit if the activity of sharing one’s faith is both permitted and conducted with respect. But there is much work to do before such a conclusion is broadly accepted.

(Thomas F. Farr, a former American diplomat, is visiting associate professor of religion and international affairs at Georgetown University and senior fellow at Georgetown’s Berkley Center for Religion, Peace, and World Affairs. A version of this column originally appeared at http://www.washingtonpost/onfaith.)

Eds: a version of this column originally appeared at On Faith, an online conversation on religion and politics sponsored by The Washington Post and Newsweek (http://www.washingtonpost.com/onfaith).