The opposite of civilization is human nature.
And occasionally, regrettably, human nature finds a way to break through the behavioral, cultural, social, and even religious boundaries constructed assiduously around it.
We define this “breaking through,” as conflict, violence, and—at the nation-state level—war.
The purpose of civilization is to hold back the tides of human nature and to negotiate the consequences of human nature when it runs amok: selfishness, greed, vanity, pride, sloth, envy, and so on.
Civilization does this job through the application of social and behavioral norms that enough individuals agree to. Conflicts arise, of course, when the social and behavioral norms are no longer considered normal.
Cultural evolution is a constant. Human nature is a constant.
But civilization is precious, demanding, and worth defending.