This article seeks to demonstrate that the invention of double-entry accounting, during the 13th and 14th centuries in the cities of northern Italy, was at the origin of the emergence of our monetary system: the credit money system. By showing the limits of the monetary histories that currently exist, this article shows that these limits are the consequence of a theoretical unthought: that of the different dimensions of money. It then shows that this problem is particularly well defined by double-entry accounting, which explains its decisive historical importance for the history of money.