Today, most money is created as debt on a schedule by a borrower borrowing it into existence from a bank or other depository institution. This money is spent and circulated until someone puts it aside as savings or lends it a second time as existing money. Either way, as long as the money remains saved or lent, the money originally created as a loan from the bank is not available to the borrower that created it, except as another loan. The original money creation loan will be have to be paid off with the Principal of some other loan, making repayment of that loan dependent on another loan's Principal and so on, ad infinitum. Savings create an ongoing volume of Perpetual Debt for as long as the volume of savings remains unavailable to be earned on time by the borrowers that created it.
The amount of the Perpetual Debt can neither shrink nor slow down in its delivery without causing mathematically inevitable defaults. Therefore new borrowing from banks must never decrease or slow down. Otherwise people will lose their homes because of a mathematical shortage of Principal.
Our money system is only functional when it is growing. It cannot handle shrinkage, or "de-growth" as some call it, without defaults. That makes it ill-suited even for normal economic mood swings which should be expected to be cyclical simply because everything in the Universe is cyclical.
The question always asked by politicians and economists is "What causes the business cycle?" as if it should be prevented. I say it's the wrong question. Accept the Business Cycle as natural and adapt to it.
The question to ask is:
A money system dependent on never ending growth is absolutely suicidal in a world
next ~ Money is created as a promise to pay it back