The Free Market
I love this description of the free market (as used when discussing derivatives).
One of the fundamental assumptions about the free market (itself a mathematical model, not reality, but one that reality can be measured against) is that all information is available at all times to all participants, producers and consumers alike. To use an example, think of a farmers market. The shoppers can compare the fruits and vegetables, the farmers can weigh the number of customers against the size of their inventories, and so on. Ultimately the guy with the best apples gets the best price. (And, of course, customers don’t mind bruised apples will get them at a different, lower price. They make perfectly good applesauce.)