This thesis studies the 100% money proposal, such as it was formulated in the United States in the 1930s by Henry Simons, Lauchlin Currie and Irving Fisher in particular. The essence of this proposal is to divorce the creation of money from the lending of money: deposits serving as means of payment would be subjected to 100% reserves in lawful money, awarding the state a monopoly over money creation. Because this reform idea is regularly subject to confusion, we endeavour to clarify its concept and study its main arguments. Chapter 1 recalls the history of the plan. In chapter 2, we show that the 100% money proposal ought not to be viewed as a mere avatar of the Currency School ideas: contrary to Peel’s Act of 1844, it contains no issuing rule by itself, leaving open the debate “rule or discretion”. In chapter 3, distinguishing between two broad approaches to the 100% money proposal, we show that it does not imply abolishing bank intermediation based on savings deposits at all. In chapter 4, we analyse, through Fisher’s works, the main objective of the 100% money proposal: that of putting an end to the pro-cyclical behaviour of the volume of money, caused by the dependency relationship between money creation and bank loans. In chapter 5, we study another argument of the 100% money proposal: that of allowing a reduction of public debt, by returning the totality of seigniorage back to the state—an oft-criticised argument, which, as we show, is not unfounded however. While the 100% money proposal has been arousing renewed interest since the 2008 crisis, we thought it was fundamental to clarify these issues.