Money

Money acquires value through network externalities. Dollars are mere pieces of pretty paper that are useful because people value them. You can’t eat, wear, or watch money. Yet most people actually prefer their employer to compensate them with money rather than with something more inherently useful like rice or books on game theory. If the entire human race save you became extinct, money would no longer hold any value to you, but rice would. Money has value because other people want it.

Because so many people want money, it’s useful to have it because you can trade money for goods and services. Thus, our use of money is based upon a massive coordination game.