And, whether money takes the form of silver coins, seashells, bars of gold or bank notes,
that's been true from ancient times right down to the present day.
Even lumps of clay can work better than silver coins, if people have enough confidence in them.
In Ancient Mesopotamia, nearly 4,000 years ago,
people used clay tablets like these ones to commit themselves to particular financial transactions.
For example, this one, found a little southwest of Baghdad,
specifies that a debtor will repay a lender 330 measures of grain on the harvest day.
But this one's even more fascinating,
because what it says is that a debt of four measures of barley should be repaid to the bearer of the clay tablet.
And it's that idea of repayment to the bearer that really fascinates me.