The Austrian school of economics, notably through Ludwig von Mises, proposed a monetary interpretation of the fall of Rome. In this vision, the progressive devaluation of Roman currency shattered the complex system of division of labor that sustained an empire of 60 million inhabitants. Currency, the central instrument of economic coordination, once corrupted, led to the collapse of the entire social and economic structure.

This monetary deterioration not only destroyed the empire's internal cohesion. It also severed trade links with neighboring peoples. Deprived of the benefits of trade with Rome, the "barbarians" turned from peaceful cooperation to predation. The invasions were therefore not only military in nature, but also the result of a fundamental economic breakdown.

Roman monetary history can be divided into three distinct periods. The first, from the Julio-Claudians to the Antonines (27 BC - end of 2nd century), maintained relative stability. Under Trajan, the empire reached its apogee: covering 5 million km², Rome became the first city in history to reach one million inhabitants. The denarius retains a silver purity of 98% to 80% - a moderate devaluation still allowing the economy to function.

The second period, the 3rd century, was one of military anarchy. Twenty-six emperors succeeded one another in the space of a few decades. The currency collapsed: the antoninianus, supposedly worth two denarii, contained only 1.5 in metallic weight - the first attempt to divorce legal and real value. This manipulation triggers Gresham's Law: bad money drives out good money. Citizens hoarded the good coins, spending only the devalued ones.

Archaeological evidence, such as monetary treasures, reveals this economic anxiety. Buried amphorae, analyzed through stratification, show how Romans deposited the highest-quality coins first, gradually adding more debased ones over time. These ancient "stacks" bear witness to human action in the face of uncertainty - an attempt to preserve value in a decaying world.

Constantine (310-337) attempted to stabilize the empire through radical reform. He created the gold solidus, a currency strictly controlled by the administration. Officials systematically checked weight and purity. Issuance remained limited, linked to the spoils of war. This currency became the exclusive instrument of power: taxes were paid in solidus, and legions received their pay in gold.

At the same time, the people used the bronze nummus, which was constantly devalued. In 445, a solidus was worth 7,000 nummi; in 498, 16,800. This dual system institutionalized the Cantillon effect: those with access to the solidus - the administration, landowners - were protected from inflation. The plebs, confined to the nummus, became inexorably poorer.

This monetary separation created two parallel economies with no official exchange rate. The solidus remained the unit of account, but circulated very little. The nummus, in contrast, was used for daily exchanges but constantly loses value. This monetary architecture foreshadowed the inequalities of the emerging feudal system.

Currency devaluation gradually destroyed economic specialization. Without a reliable unit of account, Mediterranean trade collapsed. Rome's specialized craftsmen could no longer trade with Egypt or Gaul. Provinces adopted their own currencies, multiplying trade frictions.

Faced with this disintegration, the urban population fled to the countryside - an urban exodus reversing centuries of urbanization. Craftsmen abandoned their trades for subsistence farming. Large estates (latifundia) became self-sufficient islands, foreshadowing medieval seigneuries.

In desperation, even Diocletian had demanded taxes in kind - the ultimate admission of monetary failure. His edict of the maximum (301) attempted to control prices, accelerating the return to barter. Economic complexity regressed to pre-civilizational forms.

Paradoxically, the solidus survived the Western Empire. Byzantium maintained it until the 11th century, ensuring a further thousand years of economic stability. In the West, its memory persists: the French word "sou" derives from solidus, a linguistic testimony to a lost monetary grandeur.

Landowners who had preserved their wealth in gold became feudal lords. Ecclesiastical structures, the only surviving institutions, provided the social bonds that money could no longer guarantee. Europe fragmented into autarkic domains, each with its own subsistence economy.

This transformation reveals the fragility of complex civilizations. The division of labor that enabled Rome to feed a million inhabitants depended entirely on monetary trust. Once this trust was broken, the edifice collapsed, returning Europe to primitive economic forms for almost a millennium.