The next element in human development is that of money and the growth of cities and trade. Why is there division of labor and why is there money? Hoppe covers why people do not remain in self-sufficient isolation even when they could and even if everybody hated everybody else. As long as every person wants to have more rather than less, division of labor occurs.
Human action itself tends toward social cooperation in aiming toward his own welfare. Sympathy is not the cause of division of labor. Uruk was the first large city about six thousand years ago, growing to around 80,000 people. Rome at its peak had a population of a million. Cities, merchants and money create civilizations.
Money puts the most marketable good in the hands of people who trade, eliminating the double coincidence of wants that was required in barter economies. A money is simply the common medium of exchange. Additionally, money permits us to engage in cross accounting. We can now determine whether we make profits or losses.
Lecture 3 of 10 from Hans-Hermann Hoppe's Economy, Society, and History.