“People define themselves in terms of ancestry, religion, language, history, values, customs, and institutions. They identify with cultural groups: tribes, ethnic groups, religious communities, nations, and, at the broadest level, civilizations. People use politics not just to advance their interests but also to define their identity. We know who we are only when we know who we are not and often only when we know whom we are against.”

Source: The Clash of Civilizations and the Remaking of World Order (1996), Ch. 1: The New Era in World Politics, § 2 : A Multipolar, Multicivilizational World
Context: In the post-Cold War world, for the first time in history, global politics has become multipolar and multicivilizational. During most of human existence, contacts between civilizations were intermittent or nonexistent. Then, with the beginning of the modern era, about A. D. 1500, global politics assumed two dimensions. For over four hundred years, the nation states of the West — Britain, France, Spain, Austria, Prussia, Germany, the United States, and others — constituted a multipolar international system within Western civilization and interacted, competed, and fought wars with each other. At the same time, Western nations also expanded, conquered, colonized, or decisively influenced every other civilization. During the Cold War global politics became bipolar and the world was divided into three parts. A group of mostly wealthy and democratic societies, led by the United States, was engaged in a pervasive ideological, political, economic, and, at times, military competition with a group of somewhat poorer communist societies associated with and led by the Soviet Union. Much of this conflict occurred in the Third World outside these two camps, composed of countries which often were poor, lacked political stability, were recently independent, and claimed to be nonaligned.
In the late 1980s the communist world collapsed, and the Cold War international system became history. In the post-Cold War world, the most important distinctions among peoples are not ideological, political, or economic. They are cultural. Peoples and nations are attempting to answer the most basic question humans can face: Who are we? And they are answering that question in the traditional way human beings have answered it, by reference to the things that mean most to them. People define themselves in terms of ancestry, religion, language, history, values, customs, and institutions. They identify with cultural groups: tribes, ethnic groups, religious communities, nations, and, at the broadest level, civilizations. People use politics not just to advance their interests but also to define their identity. We know who we are only when we know who we are not and often only when we know whom we are against.
Nation states remain the principal actors in world affairs. Their behavior is shaped as in the past by the pursuit of power and wealth, but it is also shaped by cultural preferences, commonalities, and differences. The most important groupings of states are no longer the three blocs of the Cold War but rather the world’s seven or eight major civilizations. Non-Western societies, particularly in East Asia, are developing their economic wealth and creating the basis for enhanced military power and political influence. As their power and self-confidence increase, non-Western societies increasingly assert their own cultural values and reject those “imposed” on them by the West.