Proponents of demand is side economics: if nothing were to be produced, how well would your theory work?

Well I will tell you this is how economist set it up. The barter system tends to be inefficient because of the double coincidence. With currency it helps the economy work. Money is easy because is serves a store of value, medium of exchange, and standard of deferred payment. This is what economist saw and then had them invent a fiat currency which is better than that of a commodity money because it is easily divisible.