Murray Rothbard, "What Has Government Done to Our Money?"
Economists err if they believe something is wrong when money is not in constant, active “circulation.” Money is only useful for exchange value, true, but it is not only useful at the actual moment of exchange. This truth has been often overlooked. Money is just as useful when lying “idle” in somebody’s cash balance, even in a miser’s “hoard.” (At what point does a man’s cash balance become a faintly disreputable “hoard,” or the prudent man a miser? It is impossible to fix any definite criterion: generally, the charge of “hoarding” means that A is keeping more cash than B thinks is appropriate for A.) For that money is being held now in wait for possible future exchange—it supplies to its owner, right now, the usefulness of permitting exchanges at any time—present or future—the owner might desire.
It should be remembered that all gold must be owned by someone, and therefore that all gold must be held in people’s cash balances. If there are 3,000 tons of gold in the society, all 3,000 tons must be owned and held, at any one time, in the cash balances of individual people. The total sum of cash balances is always identical with the total supply of money in the society. Thus, ironically, if it were not for the uncertainty of the real world, there could be no monetary system at all! In a certain world, no one would be willing to hold cash, so the demand for money in society would fall infinitely, prices would skyrocket without end, and any monetary system would break down. Instead of the existence of cash balances being an annoying and troublesome factor, interfering with monetary exchange, it is absolutely necessary to any monetary economy.
It is misleading, furthermore, to say that money “circulates.” Like all metaphors taken from the physical sciences, it connotes some sort of mechanical process, independent of human will, which moves at a certain speed of flow, or “velocity.” Actually, money does not “circulate”; it is, from time, to time, transferred from one person’s cash balance to another’s. The existence of money, once again, depends upon people’s willingness to hold cash balances.