What we have been witnessing in the performing arts over the past decade is the conversion of the "Now" Generation into the "Then" Generation. If the arts are truly a culture clue, then the remarkable popularity of Alex Haley's "Roots" on television isn't just an isolated windfall, but one example among many of the surfacing of a powerful riptide.

The phenomenal success of "Roots" suggests, among other things, that the past may yet become the most voguish obsession of the decade.

Only yesterday, it seems, the whole country, and certainly its cultural trend setters, had come to unanimous agreement with Henry Ford's celebrated definition of history as "bunk." But already in the last 10 years, genealogy and other forms of excavation have come closs to replacing "mind expansion," drug assisted reverie, psychoanaltyic introspection and Eastern-style meditation as the favored cultural pastimes. There's a curious hodgepodge of a movie currently on area screens called "The Search for Noah's Ark." Clearly the makers had their fingers on the public pulse. It's just one more sign of a rising enthusiasm for the tracing of ancestries and a delving into origins.

Looking back, it seems clear that the "Now" phenomenon was born out of an immediate sense of impending cataclysm, and more specifically, from the consciousness of the central geopolitical fact of our era - The Bomb. Remembre the time when every other magazine cover was warning us of Doomsday machines, speculating on overkill capacities, or measuring potential first-strike losses?It was succeeded shortly by an interval in which the headlines seemed relentlessly crammed with assassinations, riots, protests and confrontations.

The world appeared to be caught up in an orgy of self-immolation. The subtitle of "Dr. Strangelove," you may remember, was "How I Learned to Stop Worrying and Love the bomb." That was in 1964. The point is, of course, that we never did learn. Instead, the collective response was to bury one's head in the oblivious sands of immediacy. "Instant gratification" became the cry of the hour, making each present moment count, for who knew how long we had until the final countdown.

It's probably no accident that the so-called sexual revolution and the rage for pornography reached their height in the middle of all this, in the late '60s, and the public stage began to writhe with nude actors and actresses. At the same time on the nation's campuses, courses in contemporary issues and fads were rapidly displacing traditional, historically based subjects. And as the "Now" fever escalated, the disdain for history ripened into virtual contempt - if older generations had done things a certain way, it was bad because they had done so.

In music, the order of the day was rock of the most ear-splitting, mind-cudgeling species, along with the new "trance music" of the concert halls and the recrudescence of hedonistic impressionism. The rise in the popularity of dance can also be traced to those days, predicated upon an immersion in physical sensation. The theater world, meanwhile, dallied with the euphoric [WORD ILLEGIBLE] of Aquarius.

Today, however, we are living in what appears to be a greatly changed world.At the present moment there reigns internationally wht for want of a more accurate word we are obliged to call "peace." Terrible sores are festering in the Middle East, in Africa, Ireland, Korea and Eastern Europe, but bloodshed is at a temporary minimum. Not only our new President but also all his erstwhile political rivals made a return to traditional ethics and values the theme song of the recent campaign.

But notice that there is precious little mention of the future except in terms of the avoidance of past perils - war, corruption, divisiveness. The fact is that the big shadow of The Bomb still lurks morbidly in the attic of our imaginations.We may not talk about it anymore, but we cannot evade the knowledge that the human race has all the equipment it needs to "self-destruct" (to use a term in itself symptomatic of an era) 10 times over.

Why look ahead in our leisure hours when all that's visible, aside from this prospect, is the threat of insufficient food, dwindling energy and a global population multiplying beyong all tolerance? We have, for the moment, tucked away The Bomb and its stockpiles into some convenient corner of forgetfulness. Thus we no longer seek the instant surcease of the "Now." We can afford to be more leisurely about it, and instead we reach back for the security blanket of the past, in the hope, too, that its lessons may help us exercise our devils.

"Roots" offers a key illustration. It approaches the past in distinctly personal, vicarious terms. It deals with the continuously evolving fate of a single family over the course of five generations. And it attempts to examine the institution of slavery. Perhaps the magnitude of the response is occasioned partly by a feeling that cuts across racial heritage, a feeling of being enslaved by circumstance, of being disenfranchised form control over one's destiny.

The era of the "Then" generation had its inception in the nostalgia craze, which has now burgeoned into something both broader and deeper. From the Busby berkeley revivals to "Travesties," from "The Forsyte Saga" to "The Gardener's Son," from movies as disparate as "That's Entertainment" and "Hester Street," from the fictions of "Bagtime" to the facts of "The World of Our Fathers," from Paul Taylor's "American Genesis" to Eliot Feld's "The Real McCoy," and from "The Adams Chronicles" to "Roots," we see ourselves burrowing into the archives of individual and national memory, clinging to old certainties, reliving old traumas, fishing for the answers and the solace that neither the present nor the future offer promise of disclosing.

What was the Bicentennial but a prolonged rite of retrospection?

The clamor over "Roots" is a hint that the "Then" age has far from run its course. Both the "Now" and the "Then" generations have been in retreat from the same specter, though the latter has permitted itself much wider berth and less frenetic temperament. The burning question now, so far as the arts are concerned, is what things may be like if we ever get to the other side.

If there is a future, what shape will its cultural image assume? What song will be "Tomorrow" generation sing? obviously, no one can say for sure. But perhaps the answers will be conditioned as much by space as by time. If humanity does make it over the nuclear hump, the world view of posterity is likely to proceed from a new perspective, cosmic in scope rather than global. Once we begin to live and think on this scale, they very meanings of past, present and future - as qualifiers of human experience - may be radically altered. We may, for example, come to regard them no longer as mutually exclusive categories, but rater as alternative modes of perception, existing side by side and simultaneously within every instant. What our artistic sensibilities may make out of such metamorphoses is hard to imagine concretely. One can only surmise that an art focusing on the "thereafter" might be no less attractive or compelling than those which dwell on the "Now" or "Then."