The doctor was an enthusiastic amateur photographer, sporting a pricey Canon digital SLR. His college-aged daughter seemed more interested in my good-looking, single friend than in the fine points of wildlife photography, but she had a point-and-shoot camera of her own. We were in southern Kenya's Masai Mara doing what Westerners usually do there, much to the perplexity (and profit) of the local residents: tearing up the virgin veldt in four-wheel-drive Land Rovers, cameras at the ready, in search of photogenic animals.

One of the most reliable instincts of modern people, at times of surpassing transcendence—witnessing the first kiss at a wedding, watching our children's first steps, encountering a family of cheetahs gnawing on a freshly killed gazelle—is to grab a camera. At other places and times people might have written a poem, sung a song, or carved a totem pole. But we, captive to the notion that the only lasting reality is virtual, illuminate our transcendent moments with flashbulbs.

The digital age, where film is effectively free, is an era of even more promiscuous photography. By next year, the Gartner Group predicts, 80 percent of cell phones sold in the United States will include a camera. Users of camera phones don't need to wait for carefully chosen moments. Instead they collect what the rapidly growing photo website Flickr calls a photostream—a river of images both momentous and mundane.

Many centuries after the shift from oral to written culture, we are now well along in the transition to visual culture—where the predominant mode of communication is images rather than words. Just as the shift to writing required the skills we call literacy, so visual culture requires its own skills—for ...