The economy is a dynamic system which is far too complex for us to understand. Human nature is extremely complex and billions of irrational humans form the economy. How can such a system ever be thought to be inherently stable - as many prominent economists have sustained? But this system, like every other natural or man-made system, must respect the laws of physics, even if they may be unknown at a given time. One of the instruments that have enabled the crisis, and allowed it to be hidden for a long time, are sophisticated math models. There was nothing in those models that would even hint catastrophy because models can only tell you what you hard-wire into them. A Panglossian approach to finance and the economy excludes extreme events and catastrophies, allowing bubbles to grow and Ponzi schmes to flourish. So failure was not contemplated in the models. And nobody can force you to do so.