At some point, the world is going to have to bite the bullet and accept a huge downsizing in its way of life to bring the assets-to-debt ratio back in touch with reality.

When the next big problem comes online, be it the Euro crisis, nuclear proliferation, an overstretched Internet, a killer flu, or any of the other possibilities I consider in X-Events, we will suffer a complexity overload.

Trying to solve the problem by creating more debt is analogous to trying to stop being an alcoholic by going on a bender down at the corner bar.

We see an ever-increasing move toward inter and trans- disciplinary attacks upon problems in the real world ... The system scientist has a central role to play in this new order, and that role is to first of all understand ways and means of how to encode the natural world into "good" formal structures.

In fact, the very nature of an X-event is that it is both rare and surprising. So I would not say that any specific X-event is likely. What I would say, though, is that some X-event is not only plausible, but very likely in a time scale of a few years.

To function effectively, the system scientist must know a considerable amount about the natural world AND about mathematics, without being an expert in either field. This is clearly a prescription for career disaster in today's world of ultra-high specialization.

If you ask which of the scenarios I think is most dangerous, though, I will give a different answer. In that form of the question, I regard a nuclear attack, terrorist-generated or otherwise, as the most threatening combination of likelihood and long-term damage to modern life today.