Submitted by Pater Tenebrarum via Acting-Man blog,
Introducing Money
Imagine three men living on a small island. Toni is mining the local salt mine, and apart from him there are Pete the fisherman and Tom the apple grower and their families. They have a barter trading system set up: Toni exchanges his salt for Pete’s fishes and Tom’s apples, who in turn exchange fishes and apples between each other.