Images that shock and provoke

One of the points Susan Sontag maintains in this pithy yet still rather diffusively argued book is that if we are "perennially surprised" at the appalling cruelties humans inflict on each other, then we have "not reached moral or psychological adulthood." Who would want to be accused of that degree of naiveté?

At every level, "Regarding the Pain of Others" is a fiercely challenging book. Sontag's main theme is the imagery of atrocity. Her earlier book "On Photography" (1973) remains immensely thought-provoking on its subject. In this new work, she concentrates specifically on the images of violence to which we subject ourselves, and she is again immensely thought-provoking.

In the modern world, according to Sontag, the most indelible horrific images (principally of war, the "largest crime," but also of terror, famine, pollution) are likely to be photographs. Photographs shock. They accuse. They assault. They haunt. And they also document. Photographs are, or can be, detachedly objective because they are mechanically instantaneous. But at the same time, they indicate the presumed authenticity of a personal witness.

Still photographs are different from the successive and repetitive images flashed at us in the ubiquitous transience of television. They are also different from the potent make-believe of film - though filmmakers often use still photographs for reference or inspiration.

Sontag suggests that violence in paintings or prints (and she much admires Goya's "Disasters of War") belongs largely to the history of her theme rather than to the world today. The pain and sacrifice once relentlessly depicted in art were seen, she writes, as "a kind of transfiguration" that was "rooted in religious thinking." But this is entirely "alien to a modern sensibility which regards suffering as ... a mistake or an accident or a crime."

For those of us who have not experienced the dread and terror of war firsthand, she concludes that images of war "perform a vital function": "Let the atrocious images haunt us," she cries. "This is what people can do to each other. Don't forget." And she points out that to "remember is, more and more, not to recall a story but to be able to call up a picture." A photo is an "indelible sample." Unphotographed atrocities seem "more remote."

Having said all this, and with masterly articulateness, Sontag then insinuates some of the other sides of the question. Photographs don't "tell us everything we need to know," she points out. They can misrepresent and distort. For example, we can become habituated to images of horror (although she shows how this is not always the case). But "pathos in the form of a narrative does not wear out."

Then there is the dangerous possibility of "prurient interest" in ghastly images, of viewers being drawn to the gruesome while also being disgusted by it. Goya remarkably avoids this in his suite of etchings, but photographs give out mixed, ambiguous signals. They can turn other people's suffering into a spectator sport. The war photo intended by the photographer as evidence of admirable heroism may become, in certain circumstances, a rationale for protest against war. Conversely, patriotism can make a photo of terrible suffering a reason for patriotic fervor rather than opposition to war.

It's a difficult irony that shocking photographs can arouse compassion, but since they are most usually of events in remote parts of the world, they can simultaneously frustrate the action compassion demands.

Photographs are seen as the strongest kind of "realism," yet there have been times when an appalling event has been restaged to make it seem more convincing than the actual event. Sontag observes, however, that "staging" is today "on its way to becoming a lost art."

And finally she points to profound hypocrisy and double standards in the way photographers are expected to be more discreet the closer they are to home. Suffering children in Africa, for example, are photographed with a degree of frank exposure that is unlikely to be applied to similar subjects on home soil. The victims of war in a distant country are treated with less respect photographically than innocent victims of terrorism at home. Troops, if "enemies," are treated by photographers with far less "dignity or compassion" than our own. Excruciatingly, Sontag refers to "the wounded Taliban soldier begging for his life" pictured in a major American paper, yet points out that he "also had a wife, children, parents, sisters and brothers" who may one day see these photos "if they have not already seen them."

So this is a book that is as uncomfortable with our evasions and confusions as it is with the virtues and shortcomings of picturing violence. And it's not incidental that, as with her early book "On Photography," there is not a single illustration included. Words, Sontag seems to imply, can say it all. And arguably (in her hands, at least) say it better.

• Christopher Andreae writes about art for the Monitor from Glasgow, Scotland.