The principal question which Oresme sets out to answer, according to the first chapter of this treatise, is whether the sovereign has the right to alter the value of the money in circulation at his pleasure, and for his own benefit.  He begins the discussion by going over the same ground as Aristotle in demonstrating the origin and utility of money, and then proceeds to discuss the most suitable materials which can be made to serve as money.  He decides in favour of gold and silver, and shows himself an unquestioning bimetallist.  He further admits the necessity of some token money of small denominations, to be composed of the baser metals.  Having drawn attention to the transition from the circulation of money, the value of which is recognised solely by weight, to the circulation of that which is accepted for its imprint or superscription, the author insists that the production of such an imprinted coinage is essentially a matter for the sovereign authority in the State.  Oresme now comes to the central point of his thesis.  Although, he says, the prince has undoubtedly the power to manufacture and control the coinage, he is by no means the owner of it after it has passed into circulation, because money is a thing which in its essence was invented and introduced in the interests of society as a whole.

Oresme then proceeds to apply this central principle to the solution of the question which he sets himself to answer, and concludes that, as money is essentially a thing which exists for the public benefit, it must not be tampered with, nor varied in value, except in cases of absolute necessity, and in the presence of an uncontroverted general utility.  He bases his opposition to unnecessary monetary variation on the perfectly sound ground that such variation is productive of loss either to those who are bound to make or bound to receive fixed sums in payment of obligations.  The author then goes on to analyse the various kinds of variation, which he says are five—­figurae, proportionis, appellationis, ponderis, and materiae.  Changes of form (figurae) are only justified when it is found that the existing form is liable to increase the damage which the coins suffer from the wear and tear of usage, or when the existing currency has been degraded by widespread illegal coining; changes proportionis are only allowable when the relative value of the different metals constituting the coinage have themselves changed; simple changes of name (appellationis), such as calling a mark a pound, are never allowed.  Changes of the weight of the coins (ponderis) are pronounced by Oresme to be just as gross a fraud as the arbitrary alteration of the weights or measures by which corn or wine are sold; and changes of matter (materiae) are only to be tolerated when the supply of the old metal has become insufficient.  The debasement of the coinage by the introduction of a cheaper alloy is condemned.