In Economic History, the first development program of an economy is the one developed by Xenophon. In his short work "On Revenues," Xenophon proposes ways for the recovery and development of the city of Athens. The central element of the program is the exploitation of the silver mines in Laurium to increase the quantity of money. In this work, a theory of money is formulated for the first time, which can be considered as the first appearance of modern theory. For this reason, Xenophon has been characterized as the Keynes of his time. In antiquity, money, being metallic, did not cause economic crises. On the contrary, later the abolition of the convertibility of paper money into precious metal opened the door to provocative monetary crises because, among other things, central banks, firstly, are unable to accurately know the state of the economy, secondly, when there is great uncertainty, they lose control of the quantity of money and interest rates, and, thirdly, in one way or another, they are not independent of the political expediencies of governments.