Our global financial system has become so staggeringly complex and opaque that we’ve moved from a world of risk to a world of uncertainty. In a world of risk, we can judge dangers and opportunities by using the best evidence at hand to estimate the probability of a particular outcome. But in a world of uncertainty, we can’t estimate probabilities, because we don’t have any clear basis for making such a judgment. In fact, we might not even know what the possible outcomes are. Surprises keep coming out of the blue, because we’re fundamentally ignorant of our own ignorance. We’re surrounded by unknown unknowns.