Abstract (EN)

There is a duality of money : it is endogenous and exogenous. Therefore it is important to distinguish between monetary creation and money supply. Buying and selling means the exchange of goods and debts, which is very different from barter. In doing so the economic agents are asked to take two kinds of risks : liquidity and insolvability. Banks interventions in the exchange reduce these risks. When the accent is concentrated on these exchange's risks it is possible to understand the duality of money. On these bases we can study both the monetary theory and the banking theory. And it helps for a better understanding of the lender of last resort.