THE INTERROGATION TECHNIQUES used by the Bush administration in the war on terror, says the editorial page of the New York Times, have "dishonored" our history. Have we, the paper asks while wagging its finger, become "a nation that tortures human beings and then concocts legal sophistries to confuse the world"? Even if one does not share the accusatory purposes of the Times, millions of thinking Americans are wondering if the use of torture in our battle with al Qaeda is ever legitimate.

But what exactly is torture? International treaties in force, including the Torture Convention, ban its use. But torture itself remains difficult to define. This was a point driven home in the testimony given in his confirmation hearings by Michael Mukasey, President Bush's nominee for the position of Attorney General.

At a number of junctures, Mukasey offered categorical opposition to the use of torture, noting that the president cannot authorize it because it "is barred both by statute and by the Constitution." He stated specifically that it "is not constitutional for the United States to engage in torture in any form, be it waterboarding or anything else."

But at another moment, Mukasey backed away from such precision about the practice known as waterboarding: "I don't know what's involved in the technique. If waterboarding is torture, torture is not constitutional" (emphasis added). One senator obligingly explained what the procedure entails--"putting somebody in a reclining position, strapping them down, putting cloth over their faces and pouring water over the cloth to simulate

Mukasey is a clear-thinking jurist. Why this reticence? The opponents of torture paint the issue in black and white. Given what they see as at stake, i.e., nothing less than the integrity of the U.S. Constitution, U.S. law, and international law--not to mention the moral conduct of members of our armed forces and intelligence agencies, and the American "image"--they contend that we should almost certainly err on the gentle side of interrogation.

As someone who finds torture repugnant and antithetical to everything we stand for, I sympathize with that view, as surely do most Americans. But the matter, alas, is not so simple. Almost everyone, left and right, seems to agree that there are rare occasions where we might need to make an exception, and be ready to resort to harsh methods. The obvious case is the so-called "ticking time bomb." Yet even here, where the justification for harsh measures appears far more clear cut, we run into complexity.

For what exactly is a ticking time bomb? Does this term refer to any captive who has knowledge of an imminent terrorist plot? Or does it refer to someone who has knowledge of others who might know of such a plot? As we move from firsthand to second- and even third-hand knowledge of a plot, drawing a line becomes progressively trickier. And does it matter how many lives are at stake and whose? Must we not torture if we are talking about a possible IED on a road traversed by our troops in Iraq, and should we definitely torture if are talking about finding a nuclear device known to be hidden in the basement of, say, a Lebanese restaurant in New York and timed to go off in 24 hours?