The fact of difference in moral cultures is very clear, in spite those who claim all cultures are at bottom essentially the same. But sheer difference in itself does not mean that there is no universal or absolute morality. It may mean only that some are mistaken or underdeveloped and have yet to grasp true morality. So, the classical views on comparing moral cultures are three:
1) Absolutist Model: This model holds that there is one true absolute morality even though it is not identifiable with any extant version of moral culture, and indeed we may not be able to say exactly what it is. However, this universal morality is the judge of all human moral cultures. Some versions of absolutism tended to identify the universal morality with that of a particular culture. When this occurs, it is called ethnocentricism. It is best represented in Western imperialism and colonialism.
2) The Moral Relativism Model. Mary Midgley, in Heart and Mind has termed "moral isolationism" as that view that the respect and tolerance due from one moral community to another forbids us to take up a critical position of any other community's practice. Moral isolationism is a type of ethical relativism. William Sumner defends this position with two arguments: 1) There is certainly difference in moral belief. What is wrong in some communities is right in others. 2) No one has ever been able to discover what universal morality is. Thus, moral isolationism is ultimately a form of skepticism which suspends comparative judgments of moral cultures.
However, we can observe that if we accept the relativism of the moral isolationist point of view, then we will forfeit the right to criticize other communities and to provoke needed moral change. Indeed, if we are moral isolationists, we must give up any comparison of moral practices which says that one is preferable to another. Historically, speaking this would mean that we would have no grounds from which to criticize the Holocaust or to speak of moral progress when saying that slavery has been abandoned. Since we do not wish to follow this path, what avenues of moral change and criticism are open to us.
3) The Moral Pluralism Model: A third approach is to say that there is no true absolute morality, nor any extant moral culture which is inherently superior to others, but there are substantial commensurabilities between moral cultures from which judgments can be made. These overlapping moral agreements are contingent, historical and cultural, not absolute, ontological or theological. Cultures are really "just like us" and all cultures don't believe the same things. But all cultures do believe some of the same things.
As the world peoples interact more frequently and as communication becomes more comprehensive, it may well be that a growing global moral culture with increasing notice of commonalities may emerge.
But we should not make the all-to-ready assumption that the density of contacts between cultures may thicken a global culture.
This may be true. But if so, it will not be because of an invisible hand driving the process (unless one perhaps wants to take a metaphysical line of argument here). More likely, if it occurs it will be a consciously engineered process to some extent, where many moral cultural values will carry their own momentum and self-authentication because they contribute human security and hold the promise of fulfillment. Global practices, bodies of knowledge, institutions, conventions, and lifestyles may arise and yet be increasingly independent of nation-states and yet arrive at convergences in lifestyle. Surely, all difference will not and should not be eliminated.
Yet, it may be false that contact of cultures will create a global unity or agreement on morality. It is at least possible that the differences between people will drive us further apart and that they will overshadow our commonalities, perhaps even shattering them.
What will drive global interaction of moral cultures? Well, the process might be thought easier if we faced some external threat such as in Independence Day. . But what will more likely drive it is the growing interdependency of economic and institutional ties. New means of technology such as transportation and travel, as well as communication in mass media and the internet in which different cultures meet and clash will continue to raise the question of commensurability acutely. Transposable themes are already rising: youth, fitness, beauty, luxury, romance, even freedom. Global cities have already emerged where divergent cultures thrive in symbiosis: Los Angeles, Sao Paulo, Tokyo, Rio de Janeiro, Calcutta, Singapore. The walls which separate nation-states are increasingly becoming regarded as permeable.