Tinkerbell effect

The Tinkerbell effect is a term describing things that are thought to exist only because people believe in them. The effect is named for Tinker Bell, the fairy in the play Peter  who is revived from near death by the belief of the audience.

Claimed cases include:
 * private property
 * the value of a nation's money in a fiat system
 * the value of gold
 * civil society
 * the "rule of law"

Reverse Tinkerbell effect
The Efficient Market Hypothesis is regarded as a case of reverse Tinkerbell effect.