The eighteenth century was the culmination of many of the patterns that first came about in the late medieval and early Renaissance periods. The Great Powers were centralized, organized states with large armies and global economic ties. The social and legal divisions between different classes and categories were never more starkly drawn and enforced than they were by the eighteenth century. Wars explicitly fought in the name of gaining power and territory, often territory that spanned multiple continents (as in Britain's seizure of French territory in both the Americas and India).
Ironically, given the apparent power and stability of this political and social order, everything was about to change. As the ideas of the Enlightenment spread and as the groups that made up the Third Estate of commoners grew increasingly resentful of their subservient political position, a virtual powder keg was being lit under the political structure of Europe. The subsequent explosion began in France in 1789.
Image Citations (Wikimedia Commons):
Three Social Orders - Public Domain
Holy Roman Empire - Robert Alfers
Expansion of Russia - Dbachmann
Peter the Great - Public Domain