The monetary theories that stem from the works of Thomas Aquinas on the one hand, John Buridan and Nicholas Oresme on the other hand, share common roots: they appear as the result of careful commentaries upon Aristotle's moral and political works. Nonetheless, they differ on both the understanding of money as a measure of values, and on the conditions that allow the emergence of money from a stock of metals which could be, like natural wealth, allocated to different uses. Therefore, they illustrate respectively a “conventional” and a “metalist” theory of money. The question raised by Buridan's and Oresme's political representations is to make them consistent with monetary theories elaborated separately. In this respect, they supplied a composite picture in which the Prince is an essential character. Acting as the efficient cause of money, he is expected to achieve the adjustments required by the real changes affecting money. But the question of the debasements of money gave rise to different lines of answers. While Buridan concluded with an identification of the Prince and the common good, Oresme drew a Prince whose power is partly controlled through adequate institutions and incentives, partly limited by the consequences of his policy choices.