There are a finite amount of the small paper rectangles available (yes the supply is increasing, but it is finite at any moment) AND these small paper rectangles are required in order for US residents/citizens that earn income in any currency in order to stay out of prison. So, in other words, not a fiction.

And yet not all pieces of paper are believed to be equal. Some pieces of paper will buy you a loaf of bread and others will buy you a tank full of gas. The difference lies in the magic squiggles printed on the pieces of paper. In other words, the belief that a certain number value equals a fair exchange for a physical good or service. This is a consensual belief. If an extra 0 appeared magically overnight on every piece of paper, what has changed? People will believe they have “more” than they did before. If instead of magic, the government announced a policy of reissuing recycled bits of paper that have had an extra zero printed on them, would people believe they had “more”?