It is generally agreed that throughout antiquity a functioning coinage was closely associated with state power. Not only is this idea critical for explaining the introduction of coined money in the sixth century B.C., but it also underpins hypotheses concerning the possible monetary crisis in the third century A.D. For roughly the first two centuries of its existence, the Roman Empire apparently commanded a largely unassailable coinage monopoly which featured legal rates of exchange which were both enforced and generally accepted by coin users. The monetary problems in the third century were caused, at least in part, by the weakening of the central government and the related breakdown of this monopoly. However, both the idea of a third-century monetary crisis and the supposed weakening of monetary monopoly should be questioned.
Numismatic evidence is critical for understanding the monetary system as a whole in this period. In addition, there are well-known examples of third-century laws which controlled currency or related institutions such as banks, exchanges and assays. Comparing links between these two bodies of evidence reveals an important but sometimes overlooked correlation: the timing of legal actions often corresponds with reductions in coinage fineness or weight. On the one hand, it should not be surprising that fixed ratios were most strictly enforced when the state was in the most need of them – when coins were newly debased. On the other hand, this limited evidence does not conclusively prove that such laws were normal nor regularly enforced in any kind of systematic fashion. In fact, the data from several third-century coin hoards may show that officials were attempting to increase controls and fixed legal ratios – efforts which may have contributed to a growing underground economy made up of money-users who forsook the imperial coinage in favour of localised exchange of surplus commodities, precious metals and imperial coins valued at unofficial (and illegal) rates. In other words, problems with the monetary system may not have been the result of the central authority's failure to impose itself with enough force, but rather, by increasing its enforcement of fixed ratios, the Roman state undermined its own currency and jeopardised its featured place in a monetary system which included alternatives to official imperial coinage.
In light of evidence which casts doubt upon both the totality of a coercive monetary monopoly and the way in which it changed over time, it is important to ask why this assumption persists. The answer may be that historians are not unaffected by their modern context. Developments in economic theory over the past century have largely taken place within capitalist systems which operate under the imperative that the money supply must be monopolised and directed by independent central banks in order to maximise economic growth and production. This presents a challenge for economic historians who are interested in drawing upon theoretical insights from outside of mainstream neoclassicism. However, alternatives to neoclassical economics, even if heterodox, ideological or otherwise ‘old hat’, can help historians to reappraise the third-century monetary evidence – albeit with models which reflect the qualitatively different nature of ancient economies.