No society can sustain unlimited growth - none ever has. History demonstrates that expectations of infinite growth lead to collapse. Unfortunately, millennia of evidence also indicates that needed attempts to stabilize such societies run counter to the expectations of the populace and of interest groups. For that reason, such attempts at stabilization frequently fail.

The key strengths of civilizations are also their central weaknesses. You can see that from the fact that the golden ages of civilizations are very often right before the collapse. The Renaissance in Italy was very much like the Classic Maya. The apogee was the collapse. The Golden Age of Greece was the same thing. We see this pattern repeated continuously, and it is one that should make us nervous. I just heard Bill Gates say that we are living in the greatest time in history. Now you can understand why Bill Gates would think that, but even if he is right, that is an ominous thing to say.

With apologies to the green movement, "sustainability" is a myth. History and archaeology show that societies are always moving to the edge of crisis, "falling forward" through growth, but then responding often successfully to the problems created. What we can hope for is that with a somewhat more controlled level of growth, and with longer-term preparations for change, we can keep responding to the inevitable smaller crises, as they arise, and continue to postpone until later and later the, perhaps ultimately inevitable, end of our civilization.

"Hypercoherence" is one of the most dangerous threats to the long-term survival of our civilization. Hypercoherence is the close efficient linkage of all parts of the world economic, communication and transport systems. It has been crucial in the spread of great innovations, the rise of world wealth, and even the dissemination of democratic concepts and ethical values and the defeat of oppressive regimes.

These strengths, and our civilization in general, have reached an apogee with the end of the apocalyptic threats of the Cold War and the end - or at least waning - of less successful, and ultimately less "just," political and economic systems. At the turn of the 21st century we appear to be entering our greatest century, a golden age. The challenge that we face is similar to that of the Classic Maya civilization: we have set in motion a "runaway train" of success.

The possible signs of a coming collapse are the same as the greatest strengths of Western civilization: democracy, capitalism, the generally peaceful linking of world economic systems, our amazing success in harnessing the powers of nature to the betterment of the human condition in health, subsistence, longevity. These are the hallmarks of our society - its most successful elements.

On the future of the U.S., or of Western civilization in general, I tend to be quite pessimistic. I would say that today I see most of the symptoms of societies on the brink of collapse, not just in the U.S., but in the tightly interconnected societies of Western civilization - now essentially world civilization.