By William Strauss and Neil Howe.
The idea that history moves in cycles tends to be viewed with suspicion by scholars. Although historians as respected as Arthur M. Schlesinger Jr. and David Hackett Fischer have made cases for the existence of rhythms and waves in the stream of events, cyclical theories tend to end up in the Sargasso Sea of pseudoscience, circling endlessly (what else?). ''The Fourth Turning'' is no exception.
This is the third book on the subject of American ''generations'' written by William Strauss, the director of the Capitol Steps, a Washington satire troupe, and Neil Howe, a senior adviser for the Concord Coalition, a group dedicated to balancing the budget. In case you missed the previous two, ''Generations: The History of America's Future'' and ''13th Gen,'' Mr. Strauss and Mr. Howe claim that the key to understanding not only American but world history is ''a unit of time the ancients called the saeculum.'' Practically every major historical crisis, the authors assert, comes in a transition between saecula, or at distinct periods within a saeculum. This claim seems less impressive when it is revealed that one size of saeculum fits all facts. ''Eighty-five years passed between the attack on Pearl Harbor and the attack on Fort Sumter. That is exactly the same span as between Fort Sumter and the Declaration of Independence,'' they write. ''Add another decade or so to the length of these saecula, and you'll find this pattern continuing through the history of the colonists' English predecessors.'' The key to history, it appears, is the Fudge Factor.
The boomers, then, will be even harder on their children than they were on their parents. The ''final boomer leaders,'' Mr. Strauss and Mr. Howe predict, will be ''authoritarian, severe, unyielding''; ''the same boomers who in youth chanted 'Hell no, we won't go!' will emerge as America's most martial elder generation in living memory,'' they warn.
The boomers are to get their comeuppance when they are impoverished during a financial panic early in the next century. ''Following the Great Devaluation, boomers will find new ethical purpose in low consumption because, with America in Crisis, they will have no other choice,'' the authors write. Many boomers ''who spent a lifetime paying steep Social Security and Medicare taxes will be substantially excluded from benefits by an affluence test.'' Making a virtue of necessity, the aged Aquarians ''will eschew high-tech hospital care for homeopathy, minimalist self-care and the mind-body techniques Deepak Chopra calls 'quantum healing' '' -- thus perhaps accelerating generational succession.
Sometimes Mr. Strauss and Mr. Howe try to have it both ways: ''America will become more isolationist than today in its unwillingness to coordinate its affairs with other countries but less isolationist in its insistence that vital national interests not be compromised.'' At other times they hedge their bets: the ''New Silent'' generation ''could well be the first to reach other planets in a rocket fleet,'' even as ''the Fourth Turning could spare modernity but mark the end of our nation.'' All the blinking and whirring of their methodology permits them to make this daring prediction: ''The Fourth Turning will be a time of glory or ruin.'' The Macintosh has labored and brought forth a mouse. ''Human history,'' Mr. Strauss and Mr. Howe write, ''seems logical in afterthought but a mystery in forethought.'' Indeed.