From Allah by Miroslav Volf
For monotheists, to worship God means, among other things, to espouse a set of values about what ultimately matters in human life. To worship a different god is to espouse a different set of such values. A clash of gods is a clash of ultimate values. That's why the question of whether a given community worships the same god as another community has always been a crucial cultural and political question and not just a theological one. Concern about ultimate values that underpin political life explains, for instance, why a document that claims that Muslims and Christians worship different gods would circulate through the Parliament of the United Kingdom.
As the war in Iraq got under way and the tensions between Muslim communities and some Western governments escalated, U.S. Deputy Undersecretary of Defense Lt. Gen. William Boykin suggested that Allah is "not a real God" and that Muslims worship an idol. Influential televangelist and former U.S. presidential candidate Pat Robertson stated the issue sharply. Contemporary world conflicts between Islam and the West, he said, concern the matter of whether "the moon God of Mecca known as Allah is supreme, or whether the Judeo-Christian Jehovah, the God of the Bible, is supreme." The God of Muslims and the God of Christians are two radically different gods, he implied, and that conclusion ultimately explains and justifies the supposed clash between the two civilizations.
Robertson's claim that Allah is the "moon God of Mecca" is historically false and turns differences between the God of the Qur'an and the God of the Bible into a bad and damaging caricature. Nevertheless, Robertson correctly expressed the political import of a radical difference between the gods that people variously worship. At the risk of oversimplification, one may generalize the issue at stake in this way. The stronger the tensions between adherents of different religions, the more likely that their gods will be held to be incompatibly different-if for no other reason than that, in their imagination, worshippers will draw their god into those conflicts too. Inversely, the more different the gods worshipped by various peoples, the more likely, all other things being equal, that their respective worshippers will come into conflict and the less likely that they will find peaceful resolution of conflict.
The point here is not that all conflicts between communities are reducible to religious differences, let alone to the more specific difference in the understandings of God. They are not. The point is rather that the differences between gods worshipped often spark, contribute to causing, and magnify conflicts between their respective worshippers. Since in monotheistic traditions convictions about God are repositories of ultimate values, if respective conceptions of God are radically different, then ultimate values are radically different. And if ultimate values are radically different, the people who espouse them will not be able to negotiate their differences successfully and will inescapably clash-especially so in a tightly interconnected and interdependent world. The claim that Muslims and Christians worship radically different deities is good for fighting, but not for living together peacefully.
One might be tempted to say that the only workable solution is for both Muslims and Christians to secularize some of their beliefs and practices and regulate their common life without reference to God. And yet, that won't work. For one thing, many contemporary secular thinkers believe that religion is important in the modern world, because it helps forge bonds of solidarity between people. Moreover, Islam and Christianity continue to be vibrant and growing religions; even if one wanted to, one could not bypass God as the source of ultimate values.
Muslims and Christians will be able to live in peace with one another only if (1) the identities of each religious group are respected and given room for free expression, and (2) there are significant overlaps in the ultimate values that orient the lives of people in these communities. These two conditions will be met only if the God of the Bible and the God of the Qur'an turn out to embody overlapping ultimate values, that is, if Muslims and Christians, both monotheists, turn out to have "a common God."
A common God does more to help bridge the chasm between Christians and Muslims than just provide a set of overlapping ultimate values. A common God "nudges" people to actually employ those common values to set aside their animosities.