The first two assumptions made about the advent of TV were dead wrong: that it would bury radio and that it would be a threat to movies. From the start, TV has provided a generous showcase for other arts — radio performances and movies included. Millions of people who, in earlier centuries or even earlier decades of this century, would never have seen world-class ballets, operas, concerts or museum works of art have seen them on TV. Not quite the same as live, perhaps, but considerably better than nothing.

The medium's own most distinctive format bears out a theory of its first prophet, Marshall McLuhan. TV discovered that on the whole, amid all its sitcoms and music and dramas, the most entertaining, the most amusing and sometimes the most gripping thing it can show us is people sitting and talking to one another, and to us. McLuhan argued that speech is the richest form of human communication because it involves several of the senses — sight, sound, touch, etc. — and that speech on TV is the nearest equivalent yet to the face-to-face variety. Hence the ubiquitous talk show. Hence hosts with an uncanny ability to gaze into the camera and connect emotionally with viewers. And hence our feeling that we know Johnny Carson or Oprah Winfrey as we know a friend or a family member.

It's no accident that we tend to locate the defining artistic moments of recent decades in TV and other popular media, whereas in earlier decades we found them in, say, literature or painting. This stems from the other convulsion the century had in store for the arts in addition to World War I. (Oddly, it wasn't World War II. That conflict's primary impact came from the waves of European artists who fled Nazism for the U.S., enriching the country's homegrown arts and shifting the center of gravity in such fields as painting and classical music.)

The second great upheaval was the 1960s. Again, a rupture opened with the past; received standards and values were under siege, this time in the ferment of civil rights, the sexual revolution and Vietnam. In the arts the rumbling had started in the '50s, when Elvis Presley got everybody all shook up, when Jack Kerouac took to the road and Allen Ginsberg began to howl. In 1969, in a muddy field in New York's Catskill Mountains, more than 400,000 of their spiritual heirs gathered at the Woodstock Festival to stake their claim as a new generation and a new social and political force, complete with a language of their own — rock music. From then on, youth and pop culture were in the ascendant. The rock sensibility permeated the other arts — painting, film, even TV. Blacks, women and others who had been jostling on the cultural fringe increasingly moved toward center stage.

And what about the heirs of Joyce and Stravinsky? Still doing brilliant work from time to time, to be sure. But broadly speaking, the energies of high modernism had played themselves out, and the ironic, self-conscious borrowings of postmodernism did not advance the cause much. Literature, the theater, classical music lost the authority to set the cultural agenda. Today the influence, the action, the buzz is all pop.

Here's another first for the 20th century: it's the first in which performing artists at the end of the century have been able to see and hear their predecessors from the century's beginning. It used to be that only the plastic arts could be preserved — in print, paint or objects. The performing arts were evanescent. A dancer's line, a comedian's schtick, a singer's coloratura vanished as soon as the performer walked into the wings, and could only be remembered, described, perhaps glimpsed in a third- or fourth-hand imitation. Now recordings, film and videotape form a permanent database of old-time show biz. A young actor can summon up Marlon Brando's performance in A Streetcar Named Desire instead of having to read about it as a part of the irretrievable past, remote as David Garrick's 18th century Hamlet.

This sets up a new dialogue between younger performers and their artistic forebears, perhaps producing not only a deeper relish of tradition but also a shrewder sense of how to build on it — or trash it. For the rest of us, it renders a part of the past perpetually present, and it forces us to view the present differently: behind the young actor, we can't help seeing the shadow of Brando. What's more, right in front of our noses, our era, our present, is becoming part of the retrievable past for the 21st century.

Ah, yes, the 21st century. As we hurtle toward it, digital technology's dizzying capacity to shuffle, combine, alter and duplicate images and words raises ever more daunting questions for the arts. "We can scarcely calculate," critic George Steiner has remarked, "the mutations in our experience of texts, music and art in the new worlds of the CD-ROM, of virtual reality, of cyberspace and the Internet."

Will the computer make everybody a creator? Will it undermine the very idea of the individual creator whose work has form, permanence and its own essence? Or will some unforeseen nerd genius figure out how to organize all those electrons in a dazzling new way? For now, things are shifting and blurring too fast to say. True to its theme, our century, which began by changing the old constancies, ends by making change the only constant.

Executive editor Christopher Porterfield has covered the arts for TIME for more than 30 years

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