Professor Stout's brilliant concept of disagreement-based speculation calls for further developments and studies concerning implications for stability and resilience of the financial system over time. Moreover, it also suggests rediscovering and situating the socio-economic function of finance (and financing) in the economy and society. To complement this approach, we recall the European acceptance of paying differences since late nineteenth century. Derivative assets were traded in Europe, but the underlying assets (stocks and bonds) on which derivatives are built were authorized beforehand. Marteau and Morand (2010) recently appealed for reintroducing an a priori authorization procedure before new derivative assets can be marketed: this view thus inherits a century-long tradition. Eventually, it seems that a priori authorization allows for administration of systemic risk while common law-inherited rejection of disagreement-based speculation is a strong foundation for both supervisory and legal (a posteriori) decisions.