Currently reading Civilizations. It is a book with soporific word usage and flagrantly over the top sentences where the author comes off as over-impressed with himself. I would skip it if I was to make the decision again. What is a civilization is an interesting issue though. Several definitions were offered but one that stood out was:

In practice, this meant becoming progressively less violent, more scientific, and more welcome to outsiders.

It is a difficult question but the civilizations we think of as fitting the term all have a pax that go with them of one form or another. The largest of those is the Pax Romana, Pax Tartar and Pax Brittanica.

All three of those enabled massive increases in trade and consequent swapping of ideas, technologies, goods and culture. All three were exceptionally tolerant and liberal for their time as well.

However the peace of smaller and larger civilizations has come with conquest and the forcible amalgamation of legal and trading systems into the conquerors own.

Fernandez-Armesto decided to come at the problem of civilization and how to define it through ecological regions, exploring how the environment enabled, sustained and even destroyed civilizations. He comments:

A fashionable romantic myth identifies everything in early America with a form of ecological correctness and asserts that indigenous people were "at one with nature".

People everywhere adapt a variety of strategies in coping with the limitations their environments impose on them; none is inherently more virtuous or more innocent or more irrational than another; all have to manage, exploit or prey on other species to varying degrees.

The range of responses forms a gradient along an unbroken scale between ruthless adaptation of the environment to human needs, and cunning self-adaptation to the demands of the environment.

So we constantly come back to technology and the human application of it. Pretty much everything can be defined in technological terms. So the purity of humanity, the purity of ideology, the purity of politics, or the purity of culture; are all just applications of technology itself in order to allow society to continue to scale. Culture is just another human organizational technology designed to enable the humanity to scale its tribe to the increasing levels of political, social and technological advance.