This contribution examines Sismondi’s money, banking and credit theories and explores his public debt analysis (1803–1838) to connect the instability of market economy with his vision of the social contract. A detailed analysis is offered of the evolution in Sismondi’s opinion on the nature of money and the banking system, and the part it plays in his trade cycle theory. Sismondi’s monetary thought is then contextualised with a discussion of his policy-mix in relation to the Napoleonic war financing in Continental Europe. Connections with the upcoming flood of literature in England on the bullion controversy are also offered. Remarks are then suggested on the progressive emergence of an “art of public borrowing” according to which the people who provide the money also control the government. Finally, some reflections are proposed on the explicit connection established by Sismondi between budget deficits, the (ab-)use of inconvertible paper money and the partial collapse of the social contract initiated by banks and the governments using it. The entrenched instability of a market economy (discussed in an earlier article) is reinforced by the banking/credit system that works along similar line than any wealth-producing firm. Hence, thanks to the financial system, wealth does grow faster but at the expense of social justice.