For thousands of years, the primary goal of any ruler was to maximize his own wealth. The divine right of kings yielded only under the greatest of duress, as occurred at Runnymede in 1215. Premodern Europe was a maelstrom of constant warfare among small states—"nation" is too good a word to describe all but the largest. Estimates vary, but in the medieval period, as many as a thousand sovereign principalities were scattered across the continent. The clever prince or duke learned that if he taxed laborers and merchants too heavily, they were liable to take their business a few miles up the road, where levies lay lighter on the purse.
Slowly, rulers began to identify their own well-being with that of their subjects and learned not to pluck too many feathers from the goose. States that neither taxed their subjects too heavily nor seized their property too often found themselves with fuller treasuries and larger armies than states that did. Nations that could not refrain from plundering their own subjects grew weaker, and, in many cases, disappeared. Gradually, through this Darwinian process, states with enlightened taxation, rule of law, and secure property rights prospered and prevailed over their less advanced neighbors, and Europe became a good place to get rich.
-William J. Bernstein, The Birth of Plenty: How The Prosperity of the Modern World Was Created