A girl is carried from the carnage, her face invisible behind a mask of blood. The walls of the playground where she died are spattered red, and the floor is littered with shredded clothing. In a second UN schoolyard, children's bodies lie sliced like meat by falling shells.

These tableaux marked the height of the massacre in Gaza. The 40 civilian corpses were barely cold when Israel announced that it would lift its attack for three hours a day, in the first indicator that the slaughter might be reaching endgame. Israeli aggression follows a calculated pattern. Attack until global opinion becomes too restive, then do a deal.

This allows a generous helping of killing time. As the tension began to ease last Wednesday, more than 600 civilians [the death toll as of yesterday is more than 750] had perished in Gaza, while European leaders bickered and wrung their hands. The faces of the dead are a pale reproach to a world that has erased a ground rule of humanity: we have forgotten how to condemn.

Israel has attracted much tolerance from those who don't buy the argument that there is anything disproportionate in its response to Hamas aggression. Some Westerners have gazed at images of limp bodies as if they are the mortal remains of some lesser breed of child.

This response is not born of war fatigue or compassion deficit. It marks the passing of an age of certainty. The Bush presidency, with only days left to run, took the Manichean view that the world was an endless battle between the forces of pure good and those of pure evil. All human events could be seen through the prism of a philosophy devised in the third century BC and applied by a modern president beside whom the Prophet Isaiah looked pragmatic.

Iraq, Abu Ghraib and Guantanamo Bay were all by-products of a mindset that any action, no matter how brutal or immoral, is justified because it is being done by the righteous in the name of virtue. Under that credo, the horrors that can be perpetrated by a "good" state on an "evil" one are almost limitless.

In the dying days of his presidency, Bush stuck to his guns, condoning Israel's attack on Hamas. Most consider his orthodoxy discredited: they're right. The danger is that the pendulum may swing towards a world that uses Bush's tainted absolutism as an excuse to abstain ever from saying what is right and wrong. At least we knew where Bush was coming from. Behind Barack Obama's silence lies the suspicion that the incoming president will be almost as much in hock as his predecessor to the powerful Israeli lobby.

In the absence of outrage, only the Liberal Democratic leader, Nick Clegg, has urged Britain and Europe to impose an arms embargo on Israel and accused Britain's Prime Minister Gordon Brown of sitting on his hands and speaking like an accountant.

Revulsion

This is not quite fair. Brown has called repeatedly for a ceasefire. He has worked with the French and Egyptians to halt hostilities and secure an end to the blockade that has strangled Gaza. The prime minister has come close to expressing the revulsion he must feel at watching families annihilated. He can fairly claim not to have sat on the fence, as Tony Blair did when Israel attacked Lebanon.

Brown, who has (limited) form on getting tough, told the Knesset last July that Israel must pursue peace with its neighbours. David Miliband, the grandson of Jews who escaped the Holocaust, recently infuriated Israel by demanding, rightly, that food and cosmetics imported by Britain from illegal Israeli colonies should be labelled accordingly.

While Brown and Miliband could, and should, have condemned Israel more directly, governments can claim diplomatic constraints. No such problems afflict oppositions, yet David Cameron - a vociferous gunboat diplomat over the Georgia crisis - has been more muted on Israel's incursion.

What do other peddlers of sanctimony have to say about Gaza? Are our outspoken bishops too convulsed with the iniquity of shopping binges at the January sales to dwell on children with their limbs torn off? Britain's effete churchmen have been put to shame by Archbishop Desmond Tutu, who forced his way into Gaza last year and emerged calling the Israeli blockade "abominable". Though many leading Jews agree with him, expect little echo from politicians and other public figures.

The end of the Bush/Blair Manichean foreign policy should clear the way for rich, formidably armed, serial aggressors such as Israel to be stripped of automatic righteousness. Instead, the lack of outrage over Gaza suggests the dawning of an age of prevarication, in which thousands may die, in Congo, Zimbabwe, Sudan and elsewhere, as a supine world nitpicks at the smallprint of UN resolutions destined never to be passed or implemented.

Hostilities may be winding up, for now, but the danger won't stop there. If Iran is next in Israel's crosshairs, then the Middle East may implode to the sound of international foot-shuffling. But this is not simply about security. It is about humanity itself. As the tanks finally roll out of Gaza, the international community may congratulate itself on finessing the peace. The truth is that Israel has played its game exactly as it chose. If America had demanded a ceasefire sooner, or if the West had threatened embargoes and cried revulsion, then the schoolrooms of Gaza would not be graffiti-painted in its children's blood.

Bring back the politics of denunciation. Yes, Hamas is viewed by the West as a vicious neighbour. And yes, the West also has dubious warfare on its conscience. But nothing excuses acts so sickening that, if perpetrated by a less-blessed state, they would be reviled across the globe as war crimes. Once again, the world has declined to tell Israel, in terms, that it has no divine mandate for destruction.

The dead of Gaza will be buried soon. Remember them. In this new year, when the innate goodness of the human spirit is held up as the last bulwark against debt, recession, war and adversity, their ghosts should haunt us all.