Fiat

“>>"There is no commodity in the world than could underwrite the amount of M3"

Of course there is. If the money is required to pursue the goods, then there are sufficient goods to back the money. It's a two-way equation. Sound commodity-backed money is always convertible forward into goods for purchase and always convertible backwards into a tangible asset when it is held as savings. This is balance.

It is impossible for the demand for units of money to exceed the quantity of commodities and labor it is needed to purchase. There is no need to 'grow the stock' of money to keep pace with the demand for money in commerce. It is the prices that adjust up or down to reflect the ratio of money to goods.

To make a very rough example- if the money supply of a town is 100 dollars, then a dollar might be enough to buy a house, a dime a car, and a penny enough to buy food for a year. It is the prices that are elastic. The quantity of money does not need to be elastic.

100% reserve banking is entirely possible and is the only sound money, but the bankers' propaganda says it is impossible because without their freedom to create fiat or fractional reserve loans to make new revenue ( interest ) streams, the profits of banking are sharply curtailed.