The Ticking Bomb — How can society not do whatever it has to do to avoid a terrorist calamity? If we know a bomb is about to blow up the Empire State Building filled with innocent people, why read a suspect his Miranda rights? The Constitution isn’t a suicide pact, as Supreme Court justices have pointed out.

The Slippery Slope — Once we slough traditional values and standards, where do we stop? If the suspect refuses to confess after waterboarding, is it OK to torture his children to break his will? Why not, if the Ticking Bomb is about to go off? When do we stop, in the Slippery Slope situation?

Civil-liberties advocate Aryeh Neier argued in a recent Washington Post op-ed that the torture debate is pointless because neither side can prove its thesis. So it comes down to principles, and on principle he is against torture.

Interestingly, his view is supported by Sen. John McCainJohn Sidney McCainLawmakers worry about rise of fake video technology Democrats put Dreamers and their party in danger by playing hardball Trump set a good defense budget, but here is how to make it better MORE (R-Ariz.), not his natural ally on many issues, but one who comes to the torture issue from a unique perspective, having been a prisoner of war.

McCain suffered prolonged imprisonment and crippling treatment as a prisoner during the Vietnam War, so he argues from his uniquely persuasive position that torture is contrary to American law and values. McCain disagrees with those who argue that torture led to the killing of Osama bin Laden, and he quotes CIA Director Leon Panetta, who told him that “enhanced interrogative techniques” — some euphemism, that — did not lead us to Osama, and in fact “produced false and misleading information.” Use of these techniques endangers our soldiers, against whom retributive actions might be used, McCain fears. McCain argues, “This is a moral debate. It is about who we are.”

I agree with this odd couple. In a true Ticking Bomb situation — there has been none, yet — theories will fly out the window. The killing of Osama is an example. Few reasonable observers faulted the invading soldiers who acted impulsively. They, metaphorically, defused a Ticking Bomb. But questioning prisoners in the hope of discovering critical intelligence in times of terror is a different case. The only Ticking Bomb in these situations is the destruction of our moral values and constitutional commitments.

The test of a society’s morality is its commitment to constitutional values at contentious times, not as a theoretical Yes/No vote. It is there that our angels and devils come to challenge us. On this debate — the contest between the Ticking Bomb and the Slippery Slope — the greater damage to our democratic heritage and our personal souls is the lure of the slippery slope.

Ronald Goldfarb is a Washington attorney and author.