US Judge Potter Stewart will be remembered for his famous definition of obscenity and pornography at a time when the US justice system was struggling to balance freedom of expression and the state’s job to maintain public decency. He quipped: “I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description, and perhaps I could never succeed in intelligibly doing so. But I know it when I see it …” This rule applies to various aspects of our lives where rigid definitions are hard to establish or decisions have to be made under uncertainty. One has to go by rule of thumb or heuristics, or the “smell test”, which it is often called in the financial world when things look abnormal but one can’t pin anything down. People walk away from deals when things don’t smell right. They don’t wait for a regulator to conclude an investigation and nail the accused over 20 years.