Sound money is chosen freely in the market for it's saleability because it holds its value across time, because it can transfer value effectively across space and because it can be divided and grouped into small and large scales, it is money that cannot be manipulated by a course of authority that imposes its use on others. The importance of sound money can be explained for three broad reasons: 1. It protects value across time, which gives people a bigger incentive to think of their future and lowers their time preference. The lowering of time preference is what initiates the process of human civilization, that allows the humans to co-operate, prosper and live in peace. 2. Sound money allows for trade to be based on a stable unit of measurement, facilitating ever larger markets, free from government control and coercion, and with free trade comes peace and prosperity. Further, a unit of account is essential for all forms of economic calculations and planning, and unsound money makes economic calculation unreliable. and is the root cause of economic recessions and crises. 3. Sound money is an essential requirement for individual freedom from despotism and repression, as the ability of coercive state to create money can give it undue power over its subjects, power, which by its very definition will attract the least worthy and most immoral to take its reigns. For these very reasons, Fiat is unsound money, gold/bitcoin is sound money.