Unidentified child prisoner of the Khmer Rouge photographed before execution at the Tuol Sleng torture centre. Photograph: Unknown photographer/Cruel Radiance/The University of Chicago Press  The first chapter of Susie Linfield's provocative recent book, The Cruel Radiance: Photography and Political Violence, is titled A Little History of Photography Criticism; or, Why Do Photography Critics Hate Photography? The polemic, as it turns out, is a precursor to a much bigger moral argument – an exploration of the fraught ethical landscape skirted by contemporary reportage photography. But Linfield, who is director of the cultural reporting and criticism programme at New York University, has her reasons for laying into the critics.  In a recent interview in Art Forum, she said: "I teach criticism and read a lot of it, and some years ago I realised how different photography criticism can be in tone and approach from criticism of film, or music, or other cultural forms. Pauline Kael, Greil Marcus and others are very immersed in their subjects; they write analytically and critically but with love. By contrast, Susan Sontag and her postmodern heirs in the realm of photography criticism were very removed from, even hostile to, the subjects they discuss."  Sontag's On Photography (published in 1977) remains one of the cornerstones of photography criticism, as does Roland Barthes' more theoretically mischievous Camera Lucida (1980). Both books, along with Sontag's later work Regarding the Pain of Others, question the idea that graphic photographs of horror, atrocity or suffering can provoke the viewer into political action. Even John Berger, whom Linfield calls "the most morally cogent and emotionally perceptive critic that photography has produced", is distrustful of graphic images of political violence.  Faced with Don McCullin's most powerful, and powerfully disturbing, photographs of human suffering from the Vietnam war, Berger writes that "these moments are utterly discontinuous with normal time ... the reader who has been arrested by the photographs may tend to feel this discontinuity as his own personal moral inadequacy". The shock the viewer feels at his moral inadequacy, Berger argues, "disperses" his initial feelings of outrage, so that "the issue of the war which has caused that moment is effectively depoliticised". There is, of course, something to this argument – more so than Barthes' uncharacteristically bald statement that images exhibited to shock us often "have no effect at all".  Linfield acknowledges these misgivings, but rails passionately against the (mostly American) postmodernist critics who followed Sontag and Barthes, developing their suspicion about photography into one long sneer at "liberal, socially conscious photojournalists who clung to the old-fashioned ideas such as progress and truth".  Contemporary photojournalism is problematic, both in the increasingly explicit nature of its images of suffering and degradation and its uncertain role in a world where, as Linfield puts it, "we no longer have the same kind of moral and political framework" that governed our responses to the war photography of the past. For these reasons, her book only really comes alive when she moves beyond the narrow world of theoretical criticism and tackles the photography itself – specifically, the role of photojournalism in a world where the old certainties no longer apply and the violence of faraway wars often seems nihilistic.  Linfield's critical gaze ranges far and wide, from images of the Holocaust to photographs from Abu Ghraib. She tackles, at some emotional cost to herself, "the onslaught of images from the Muslim world that celebrate suicide bombings, beheadings and other forms of barbarism". She also writes passionately about the moral reportage of the great Robert Capa, perhaps the most influential and admired war photographer of the last century – though problematically she cites Capa's most famous photograph, The Falling Soldier, as the "classic war image, as well as the classic anti-war image, of the twentieth century" without alluding to its contested context. Capa biographer Richard Whelan refuted the suggestion it had been staged, as many suspected, but concluded he was snapping soldiers "fooling around" for the camera when a sniper's bullet killed Federico Borrell García, who "stood up for what was intended to be a heroic photograph".  The Cruel Radiance is divided into three sections: Polemics, Places and People. In the third, she contrasts Capa's work – his heroic approach and the results it produced – with the more graphic and morally complex images taken by two contemporary photojournalists, James Nachtwey and Gilles Peress. In their different ways, Nachtwey and Peress have responded to the brutality and horror of modern warfare and suffering by getting closer to that brutality and horror, to what Linfield calls "the physical agony" that so troubled Berger.  She calls Nachtwey "the Catastrophist" and it is not hard, when confronted by his photographs, to see why. It is difficult to look at many of these explicit images of contemporary warfare and suffering without being bewildered or even repulsed. And as photographs of political violence have become ever more explicit and shocking, our responses have become ever more muddled.  Linfield insists that we should look all the same and, in doing so, somehow learn to see more clearly the people in them. "If we want to construct a politics of human rights that isn't merely an abstraction, we need to look at these photographs of suffering, degradation and defeat," she said recently. "We need to think clearly not only about the relationships among these images, how they function and what they communicate in aggregate, but about the specific conditions each one depicts, no matter how disturbing, shaming and bewildering an experience that may be."  At its best, the passionate intensity and intellectual rigour of Linfield's writing may convince you that looking away, or not looking at all, is not an option. To make sense of a violent world we must, she contends, "look at, and look into, what James Agee called 'the cruel radiance of what is'". Whatever the cost.  Veteran Magnum photojournalist David Hurn has been taking photographs for 55 years. According to the press release his latest show, Passing Time, currently on at the Third Floor Gallery in Cardiff, "has been born from Hurn's will to prove that he is not as dead as some may assume, but is instead observing and photographing every day". Pairing early and late photographs from his long career, the show proves this is indeed the case. It opens on 19 November. An attendant exhibition of paired images by Hurn has been curated by members of the public; this opens on 3 December.  • For more details on The Cruel Radiance, visit the Chicago University Press website.
Sean O'Hagan: Susie Linfield says modern writers dismiss images of suffering. But photojournalism forms a basis for our human rights debates