Remember the days of old, consider the years of many generations: ask thy father, and he will shew thee; thy elders, and they will tell thee. Deuteronomy 32:7 (The following Theory of generations and cycles of history is from the book Generations by Strauss & Howe).
There are four types of generations that repeat themselves and four parts to each cycle of history. The 4 parts of a historical cycle: 1) springlike HIGH 2) long hot summer of a SPIRITUAL AWAKENING 3) cooling off of the autumnlike UNRAVELING and 4) the cold winter CRISES. The 4 types of generations are Adaptive, Idealistic, Reactive and Civic. Aslo, there are four parts to the Crises Era-the Spark, Regenerance, Climax and Resolution. We are now in the crises era of our four part cycle. The spark was 9-11. We are living through the regenerance (War-on-terror, Katrina, Swine flu scare, energy crises, the "great-recession",etc.). The climax is always a war where you can't afford to loose.