If the phrase sounds familiar, then it should.
Just take a look at a ￡20 note.
Bank notes have next to no intrinsic worth.
They're simply promises to pay, just like the clay tablets of ancient Babylon four millennia ago.
On the back of the $10 bill it says, "In God We Trust".
But it's not really God you're trusting in.
By swapping your goods or your labour for a fistful of these things,
you're trusting the US Treasury Secretary not to repeat Spain's mistake and produce so many of the damn things
that by the time you come to spend them, they're worth even less than the paper they're printed on.