Fiat money is an illusion that looks like real money when it changes hands, so you believe it's tied to something real and exchange something real for it.

The illusion is all well and good until things start to break, and you need the real thing, only to find that there isn't any real money at all. There's just debt and the false promise of real money to pay it back. The fiat economy can never stop moving or else the illusion will dissipate.