When you have a private central bank such as the Federal Reserve System (which is no more "Federal" than Federal Express) issuing the public currency at interest, then the moment that first printed piece of paper goes into circulation, more money is owed to the Federal Reserve than actually exists. As new borrowers are found to allow creation of more currency, the interest on the old money gets paid in what amounts to a giant pyramid scheme, but in the end, the cumulative debt always outstrips the available currency.
That is the trap.
The system works as long as ever larger pools of new borrowers can be found to create new money to pay the interest on the old money. But when everyone in the country (or planet) is already a borrower and nobody will borrow any more, then the pyramid collapses which is what is happening right now.
The scale of the swindle by the Federal Reserve makes Bernie Madoff-with-the-loot look like a kid who wraps scotch tape around their fingers backwards to grab a coin from the church collection plate as it passes by.
But despite its size, the central bank system is a pyramid and doomed to collapse like one.
"I am a most unhappy man. I have unwittingly ruined my country. A great industrial nation is controlled by its system of credit. Our system of credit is concentrated. The growth of the nation, therefore, and all our activities are in the hands of a few men. We have come to be one of the worst ruled, one of the most completely controlled and dominated Governments in the civilized world no longer a Government by free opinion, no longer a Government by conviction and the vote of the majority, but a Government by the opinion and duress of a small group of dominant men." -Woodrow Wilson, after signing the Federal Reserve into existence