Most historians, and virtually everyone on the political left, views most human interactions as zero-sum (borrowing a term from game theory): one person's gain is another's loss.

In fact, the potential for positive-sum interactions (where both people gain) always exists everywhere there are human beings. There are impediments -- oppressive governments, war, plagues, etc. -- but people naturally exploit opportunities for mutually beneficial exchange. They create markets, languages, the rule of law and other institutions that promote non-zero-sum outcomes.

Just as biological evolution tends toward increasingly complex life forms, human cultures evolve greater economic and technical complexity. Two factors determine the speed of this evolution: (1) how fast new ideas arise and (2) how quickly they spread. The latter, in turn, is limited only by barriers to transportation and communication.

These insights help explain why large empires, such as the Roman Empire, had salutary effects on the people they governed:

• By eliminating small-scale wars in the provinces (Pax Romana), ancient Rome allowed people over vast distances to exploit opportunities for trade.

• And by building a vast network of roads ("all roads lead to Rome") the empire greatly lowered transportation and communication costs.

However, the fall of Rome was not the disaster Romans claimed. Rule by "uncivilized" Goths, Huns and Vandals wasn't all bad.

• By the end of the Western empire, Rome was stagnant and decaying because its parasitic and oppressive government stifled free enterprise and left much positive-sum potential untapped.

• The new barbarian rulers were better economic managers; rather than imposing destructive economic policies, they replaced the Roman tax collectors and otherwise left the peasants alone.

And during the Middle Ages, the relative peace of the decentralized feudal system allowed people to develop markets, invent new products (including the printing press) and exploit opportunities for positive-sum interactions.

Source: John C. Goodman (president, National Center for Policy Analysis), review of Robert Wright, Nonzero: The Logic 0f Human Destiny (New York: Pantheon, 2000).

For text http://www.ncpa.org/oped/goodman/jcg082800.html