The objective of this article is to identify the monetary plurality in economic theory. We will try to throw light on the way in which theories are attracted towards both unicity and plurality, and more specifically by unification and diversification of money. It should also be noted, in this respect, that the economics of money has undergone considerable development since the 1970s. A survey of the diverse theories, whether mainstream or not, static or dynamic, holistic or individualistic, will reveal the surprising amount of attention devoted to the problem of monetary unicity and/or plurality. We base our presentation on two lines of thought: -The first of these lines concerns a situation of general equilibrium, as opposed to theories gi...