FOURTH TURNING IS HERETwenty five years ago, Neil Howe and the late William Strauss dazzled the world with a provocative new theory of American history. Looking back at the last 500 years, they'd uncovered a distinct pattern: modern history moves in cycles, each one lasting roughly eighty to one hundred years, the length of a long human life, with each cycle composed of four eras or turnings that always arrive in the same order and each last about twenty years. The last of