In his latest Washington Post column, Richard Cohen joins the ranks of those who argue that the use of torture in terrorism cases can sometimes be justified. Although conservatives have been more inclined to embrace that tactic since 9/11, Cohen is hardly the only liberal to be receptive to “enhanced interrogation techniques,” the Orwellian euphemism for torturing suspects.

He explicitly takes issue with an article in the New York Review of Books by Steve Coll, the author of Ghost Wars, in which Coll argues that “even if torture worked, it would never be justified, because it is immoral.” Cohen asks:

Really? Is it immoral to waterboard someone who knows of an imminent Sept. 11-type attack? Wouldn’t it instead be immoral not to doeverything in your power to avoid the loss of thousands of lives? Torture in that case might be hideous, repugnant and in some rarefied way, still immoral, but I could certainly justify it.

That argument is disturbingly flawed. Cohen—and others who share his view—set up a bogus “lifeboat” example. (That is the rigged intellectual exercise that professors of philosophy or ethics are fond of posing for their students: “If you and another person are stuck in a lifeboat, and there is only enough food and water for one person, are you justified in killing your fellow passenger?”) In Cohen’s case, he posits that interrogators know that not only is an attack on the scale of 9/11 imminent, but that the suspect they are interrogating has important knowledge about that attack.

Lifeboat examples are both artificial and largely useless in the real world. In the case of the situation Cohen sets up, there is no way interrogators can be certain of either aspect. What those who use a 9/11 lifeboat scenario are really saying is that if interrogators believe that an attack is imminent and think that the person in their custody has crucial knowledge about the plans, it is okay to torture him. That attitude leads to not just one but several slippery slopes.

One such slope involves the degree of confidence that torturing a suspect might prevent an attack. Even with the strong due-process protections in the U.S. and state constitutions, innocent parties are prosecuted—and sometimes convicted—with disturbing frequency. Many of those cases involve false confessions obtained under duress. It is far more likely that such miscarriages of justice will occur if the prohibition against torture and other due process requirements are not in play. Just how confident do authorities have to be that the suspect is a terrorist and that he has the required knowledge? Is overwhelming evidence required? Or just probable cause? Or merely reasonable suspicion? Given national-security incentives and pressures, it probably would not be long before the weakest standard became the norm.

A second slippery slope will be the temptation to employ torture in terrorism cases involving possible smaller-scale attacks. If the tactic can save “thousands of lives” by preventing a massive attack, why not use it if it might save hundreds of lives? Or even dozens? Once the ethical barrier is breached, it would be very difficult to stop zealous national-security personnel from widening the use in the name of combating all possible manifestations of terrorism, however small the scale.

Yet another slippery slope is that if it is acceptable to use torture in terrorism cases, it will become easier and more tempting to use it in other settings. Why not, for example, involving cases of child abduction, when a child’s life might be in danger? Or how about using it to break up drug gangs that engage in turf fights that often kill innocent bystanders?

Those who argue that torture can be confined to extreme terrorism cases need to look at how often other measures have been expanded, even perverted, over time. It is doubtful that the congressional authors of the Racketeer Influenced and Corrupt Organizations (RICO) statute intended that it would be applied against antiabortion demonstrators, but attempts have been made to do just that. When Congress passed the Trading With the Enemy Act during World War I, it is unlikely those legislators imagined that a president would use it more than a half century later to impose wage and price controls, but Richard Nixon did so in 1971. Proponents of the PATRIOT Act touted it as an essential weapon in the war on terror, but it is revealing that surveillance and other provisions of that law have been used in far more drug trafficking cases than terrorism cases—1,618 of the former, only 15 of the latter.

The emotions of Cohen and other proponents of using torture in exceptional cases to save lives are understandable. But giving in to those emotions has a corrosive effect on American society in multiple ways. Perhaps most important, it would gradually make the constitutional prohibition against torture a dead letter. That is a price no American should be willing to advocate.