The recurrence of ever more destructive economic crises and patterns of pervasive indebtedness and inequality threaten the social fabric of our societies. Our main responses to these trends have been partial, focusing on symptoms rather than causes, often exacerbating rather than improving the underlying socio-economic dynamics. To reflect on these conditions and on 'what needs to be done' this article turns to a similar socio-economic malaise faced by the city-state of Athens in the 6th century BC. Most historical studies dealing with this crisis focus on the comprehensive debt relief policy (seisachteia) implemented by Solon. We argue that this debt relief, although necessary, was the least important of Solon's reforms. Solon read the problem of debt as a problem of money so he went on to reform the monetary and exchange system. However, he did not think that these reforms alone could restore socioeconomic sustainability. For this, a redefinition of what was counted as valuable economic activity and as income had also to take place. Moreover, for all these to work, citizens had to be involved more in the commons. Far from only achieving socioeconomic sustainability, these reforms gave rise gradually to the demos that we meet in the golden age of Democracy. Such a broad historical horizon may help us grasp better the problems, stakes and challenges of our times.