One of the effects of the end of the Cold War in 1989 on international relations (IR) was the reemergence of religion as a social phenomenon to take into consideration in the study of this discipline. The standard version of IR history until then was that religion had been expelled from IR with the Treaty of Westphalia. This widely accepted understanding of Westphalia, along with the secularization thesis that was riding high in social sciences departments, had excluded religious phenomena from IR studies. The 1990s saw the reverse of this exclusion, with important authors such as Peter Berger (sociologist and theologian) recanting from the secularization thesis. In 1999 Berger edited the book The Desecularization of the World. The book showed ways in which modernization had strengthened religion and allowed religious actors to return to the IR arena.
Theologians should welcome the de-privatization of religion, particularly theologians interested in ethics. Theological projects such as Metz’s Political Theology or Liberation Theology (in its different brands) intended to de-privatize theology and recuperate the public dimension of the Christian faith. However, a problem arises when this de-privatization results in some type of violence.
Some 20 years ago, Scott Appleby, professor of history at the Keough School of Global Affairs published The Ambivalence of the Sacred in which he mapped the terrain of violence and religious peacebuilding. In doing so, he affirmed that the two most prominent types of violence associated with religion are ethnonationalism and religious extremism. The second type covers forms of violence that generally are labeled as fundamentalism; forms of violence that are exercised by non-state actors whose purpose is to build up an alternative to what they consider a corrupt world. The most recent and infamous case of this violence would be ISIS.
More subtle ways of violence are found in ethnonationalism. In ethnonationalist violence, the mobilization power of religion is brought in cause for non-religious or primarily non-religious goals, but in the interest of an ethnic or a national group. Alfred Smith argues in “The ‘Sacred’ Dimension of Nationalism” that religious traditions, through their narratives, practices and experiences about the sacred, sometimes consciously or unconsciously, lend the materials for the building of the sacred properties of ethnic or national identities. Smith delineates national identities as “the maintenance and continuous reproduction of the pattern of values, symbols, memories, myths, and traditions that compose the distinctive heritage of nations and the identification of individuals with that heritage and those values.”  Smith gives a good number of examples of how Christianity has contributed to shape the national identities of different countries through narratives of election, the sanctification of certain territories or the attribution of martyrial status to certain glorious dead. All these traits, along with religious and para-religious festivals, practices and experiences, contribute to build the sacred dimensions of the ethnic group or the nation.
We cannot ignore the positive contribution of the Christian faith to the shaping of many nations around the world, and we should welcome this positive influence in shaping cultures, identities, as well as social practices and experiences. However, a right witnessing of Christ’s resurrection, cannot ignore, that as the second century Epistle to Diognetus affirms, Christians: “are not different from other people in terms of their country, language or customs” and that they “live in their respective countries, but only as resident aliens, they participate in all things as citizens, and endure all things as if foreigners. Every foreign territory is a homeland for them, every homeland foreign territory.” This admirable way of living was certainly strange in the ancient world, to the point that Christians were accused of atheism for their refusal to attribute divine qualities to the political society. In our days, Gaudium et Spes 43 has recuperated the idea of dual citizenship for Christians, exhorting them to discharge conscientiously their earthly duties, without forgetting that “we have here no abiding city but seek one which is to come.”
In an age in which religion has come back to the IR, moral theology should be critical of any kind of ethnonationalism, that enlists the Christian faith for purposes that should not be recognized as Christian, particularly when this is used to justify a weaponization of religion. Claiming a public role for the Christian faith cannot make Christians forget their dual citizenship and the obligation to reject any kind of idolatry. The weaponization of religion though the divinization of the political community that allows the mobilization of the social power of religion in favor of violence is idolatrous and contrary to the ancient Christian conviction that disciples of Jesus the Lord live in the world but do not belong to the world.
 Smith, A. (2000). The “Sacred” Dimension of Nationalism. Millennium, 29(3), 803-814.
 Epistle to Diognetus, 5.