There is a widespread impression today that the history of economics is a sequence of revolutions and counter-revolutions, successive schools rising to dominance just to be deposed in a crisis by another school. According to this view, paraphrasing Marx, all history of economics is a history of school struggles, punctuated by revolutions.
If one could be perfectly certain that everybody always stays within his budget constraint, everybody could be allowed to obtain goods without a specific quid pro quo.
Money is here called the a medium and not, as customary, a unit of account because, clearly, money itself is not a unit, but the good whose unit is used as the unit of account.
Economics should be under no illusion that central banking will ever become a science.