Financial history is punctuated by crises which, cyclically and systematically, raise the question of how to regulate financial players. Whether we’re talking about the October 1987 crash or the subprime crisis (2007–2009), crises give rise to regulatory responses that are rarely satisfactory: firstly, because it’s illusory to imagine that we can foresee the causes (and therefore the solutions to the problems posed, which are always dealt with a posteriori); secondly, because the theoretical framework mobilized to think about and deploy financial regulation proves inadequate.