In the last three decades, photography's hold over the minds and hearts of millions of people increasingly has become an important subject for artists who don't necessarily think of themselves as photographers.
The changing meaning of photography at the end of the millennium is a fascinating subtext of tonight's PBS broadcast, "American Photography: A Century of Images," which examines the tremendous impact photography has had on life in the 20th century.
Photography can inform, educate, inspire and entertain because it is good at persuading us of the truthfulness of what is presented.
But photography's illusion of truthfulness is just that -- an illusion. And like any clever counterfeit, if allowed to, it can eventually take over, substituting itself for the genuine thing.
The Pop artists of the 1960s were among the first to investigate seriously the ways photographs had come to dominate the public's perception of reality.
Andy Warhol broke new ground by incorporating photographs, labels and other images from popular culture into his paintings.
Warhol's portraits of celebrities such as Jacqueline Kennedy and Marilyn Monroe were taken directly from grainy news photos he transferred to canvas. In doing so, Warhol called attention to the graphic qualities of photography that make us accept an image as "real," while also suggesting how artificial those qualities are.
From the 1970s on, artists came to see photographs as just another element in a visual environment dominated by media images.
Feminist artists used photography to criticize the way women have been portrayed in Western art, creating images that subverted conventional ideas of male dominance and female passivity.
Cindy Sherman's "Untitled Film Stills" series, begun in the late 1970s, depicted the artist as a character in situations that recalled B-movie heroines of the 1950s. Her pictures obviously were not self-portraits, since they were intended to conceal, rather than reveal, their subject's identity.
By calling attention to how identity is constructed to meet society's expectations, Sherman's photographs turned their own inauthenticity into a criticism of sexual stereotypes.
Sherrie Levine has also used photography to criticize society by undermining the credibility of the camera. She took pictures of famous photographs and claimed them as her own, justifying this "appropriation" on the theory that since only men had been "great" photographers in the past, taking pictures of their pictures would make her "great" as well.
Levine's tactic may seem extreme, but it should be remembered that many artists, including Warhol, Robert Rauschenberg and Jasper Johns, also freely appropriated images they did not themselves create.
How future generations will regard these approaches remains to be seen. But one consequence for photography at present is a general feeling that pictures can only be trusted so far.
It's probably wise to be a bit skeptical. But we also give up a lot when we give up the illusion of photography's truthfulness, because that makes it more difficult to trust in what the camera does do surpassingly well.
In an address at the Baltimore Museum of Art last year, photographer Roy DeCarava expressed dismay over the direction contemporary art photography has taken.
"I don't mind that there's been a breakdown of the forms we once tended to use as guideposts," DeCarava said. "But you have to replace them with something else that should be better. And that's not happening.
"I think the culture has lost a kind of humanism that was very important to us. We lost it to the concept of process, which has become all-important -- how we do rather than why or what we do."
The photographic image, formed according to physical laws of optics and chemistry, has the authority of a natural phenomenon, like the reflection in a mirror. That authority can be used for good or ill, but what this century has shown is we depend on photography too much to distrust it entirely.