The main goal of this thesis is to provide a clear basis for the analysis of alternative currencies, such as Bitcoin, LETS, Local currencies, the WIR or Carbon currencies. It attempts to determine whether alternative currencies might constitute just and workable alternatives, either in the form of small-scale experiments or in the form of more radical reforms. The first chapter proposes a new way to classify currencies. The second examines the case in favour of monetary plurality. The third analyses the (...) claims in favour of restricting the use of money locally, within a community, or to certain goods. The fourth studies the link between money and the market. Finally, a post-scriptum focuses on Bitcoin and cryptocurrencies. This thesis highlights that these currencies are drivers of several potential conflicts. Their widespread use might conflict with the adequate management of monetary policy, with social justice, and with liberal values. These conflicts are potential, for they would come into existence only if alternative currencies increased in scope. However, there is no reason to disregard potential conflicts when the case in their favour relies mostly on their potential benefits. (shrink)