I will start by delineating what I consider the geographic limits of the West. I consider this area to include Europe and North America, and including the descendants of European settlers in other parts of the world. The west is more a cast of mind than a geographical area. The West is defined more by its attitudes than location. North America is included because of the strong European influences on its present society, but historically the west is centered in Europe.
These attitudes are characterized by an openness to rational scientific inquiry, the acceptance of certain universal rights, and a tolerance for dissenting views. It is also characterized by the relatively highly developed material position of westerners. The West enjoys and expects a certain standard of living.
Western Civilization as it exists today is the culmination of thousands of years of societal development with its roots going back to the ancient Greeks. Greece is what I consider to be the cradle of Western Civilization and not Mesopotamia. The traditions of the West flow directly from Greece to Rome, to the Catholic Church, to the secular states of Europe to today. Western Civilization is by no means monolithic or static, it continually changes to meet new circumstances, and there is continuity with the past and an appreciation of where it came from. I hope and pray that Western Civilization is not losing its vitality and I think it is not, instead I believe it is in the midst of a search for change such as happened during the Enlightenment and Renaissance.
That is my definition of Western Civilization.