It would help, first of all, to understand what money is. Not many people seem to, unfortunately.
Look around you right now and see how little money matters in your life, physically. You don’t eat it. You don’t wear it. Your house isn’t made of it. You don’t burn it for heat or consume it directly as any other kind of energy source or fuel. You don’t walk on it; the streets aren’t paved with it. It probably doesn’t even hang on your walls as art, and it’s certainly not growing on an ornamental tree in your garden. It has next to no value in and of itself. You can’t even stuff it into a mattress to help yourself sleep better.
Money is a medium of exchange. Yeah, we all know that, right? It’s something that we obtain to trade with others for the things that we want. And that’s how you use money to get your house, your food, your transportation and all of the other things and services that you want. You do or make something, and someone pays you for the time you put in or the thing you made, and so on and so forth. Cycle of life. Got that.
But most money never exists in the real world. I do not have the figures handy – anyone who wants them can probably look them up online – but the value of “all currency in the world”, that is, all of the coins and printed bank notes that we recognize as cash, is only a fraction of “all money”. Most money is simply bookkeeping entries in various ledgers. (And even the ledgers are now “virtual”, too.) Most of us are paid nowadays via direct deposit transfers from an employer to a bank, and that is very representative of most money transactions these days: balancing transfers from one account to another, which are never represented in actual currency, no cash or coins required. Aside from our salaries, credit card purchases (and payments), car payments, mortgage payments, rent and utility payments, stock investments, even more and more grocery transactions – including purchases made with EBT and checks – do not involve cash in any form. You don’t pay taxes in cash. You don’t invest for retirement or pay your Social Security “contributions” in cash. Likewise, you don’t receive government payments in cash, either.
So where does the money come from? It is literally created out of thin air – and confidence. I’m not going to describe the entire Federal Reserve process for money creation in the United States (which has parallels in other nations, too), but in simple terms, the Fed creates accounting transfers to its member banks – essentially, loans – which represent the creation of “first money”. Those banks then look for customers to borrow that money, to be repaid at interest so that the Fed member bank can pay back its “loan” and generate profit for itself. And so on to other banks and ultimately to businesses and individuals who borrow money with a promise and expectation to repay their lender over time.
Each of those “first money” transactions creates money that never existed before. And that creation happens with some unpredictable regularity. But manufacturing money in that way is not what makes everyone rich – or we could all be rich as simply as that.
The fact is that we are awash in money. There is more money in the world than anyone knows what to do with, which is reflected in the low interest rates charged to credit-worthy borrowers. “Not enough money” isn’t much of a problem. The problem is that more and more of those loans made down the money lending chain get tied up into bad investments: houses that owners can’t pay for; businesses with no hope of turning a profit; roads and bridges to nowhere; inventory that no one will ever buy, and so forth. You can name your own list of wasteful spending and bad investments, because they’re all around. Foreclosures on these bad investments leaves banks and others holding property in which much money has been invested – but which aren’t worth that much money any more, and for which the loans will never be repaid. So that money, in effect, “dies” … but because of the nature of the system, someone has to account for that money, sometime.
Of course, a lot of the money in these accounts exists as accounting transfers from taxpayers to the government, between and among various government entities and back to government clients: Medicare and Medicaid recipients and their doctors, Social Security payments to retired and certain disabled people, government employees, including the Armed Forces, all government vendors, and some “held in reserve” in various accounts for future pension, salary and capital goods payments.
Those examples of waste – and the uncertainty of the government to meet its own future obligations – add up to undermine the other part of what money is: confidence. Aside from the accounting entries, which an elementary school child could do (even with Common Core arithmetic), the other part of “what makes money” that I mentioned earlier is the confidence that people have that it has some intrinsic worth. There is an idea, that is, which people maintain that “money is a store of value” that can be traded for other things that we value. That confidence is vital to maintaining a value of money. When people realize, for example, that there is simply no way in the world for the United States – for one example – to repay its commitments to Social Security recipients, to Medicare service providers, to Defense contractors, and so on, then confidence drops. That can happen very quickly.
Loans in our culture are made on the basis that money will be repaid with money of “similar” value, plus a small-medium-or-large interest charge to represent risk of default on the loan plus a profit for the lender. We expect that the government will always be solvent and meet its own obligations; that’s fundamental to the entire banking and monetary system. But we recognize that things are always changing, and a long term loan that won’t be paid back for many years is going to be paid back with dollars whose value is diminished by “some” inflation. So interest rates rise in accordance with lenders’ anticipation of future interest, and a lot of that depends, as noted, on confidence in the future economy and the value of future money. (@zenvelo had this exactly backwards. Interest rates do not cause inflation – at all – they merely reflect lenders’ anticipations of its corrosive effect on the value of their future payment streams.)
When enough people start to realize that the loans that they’ve made (or taken) can’t be repaid, then confidence in the whole monetary system starts to evaporate. At that point, money becomes a lot more valuable to those who have it, and harder to get for both of the reasons that @Jaxk mentioned: interest rates rise to reflect the uncertainty, and lending rules and qualifications for borrowers become very tight. (Alternatively, the other thing that creates a similar lack of confidence is when the government issuing the money in the first place does that without regard to the dilution effect of the new money on the existing stock. To illustrate this, imagine that you’re playing Monopoly and you have, let’s say, $1000 in Monopoly money. If the players all agree to raid the bank for, say, $1,000,000 in Monopoly money, then who cares that the Railroads cost $200 to buy, or that Boardwalk with a hotel on it costs $2000? The money has very little value at that point – in the game, anyway.) When the value of bank lenders’ current dollars are perceived to be worth far more today than they will be in some future “tomorrow”, then their demands for additional interest increase as well. At that time – and only at that time – will the banks pay their depositors a higher rate of interest, too.