It's a question at least as old as democracy itself: When does the cost of security become too high for a nation dedicated to protecting individual liberty?

According to some, the Bush administration has reached that threshold with its anti-terrorism proposal, which Congress is now debating.

As they move forward, our elected officials need to consider -- thoughtfully and carefully -- the relationship between liberty and security. The fact is: Liberty depends on security, and freedom as we know it in America depends on eliminating the threat of terrorism from our lives.

Yes, lawmakers must do everything in their power to preserve the basic liberties protected by the U.S. Constitution, such as the right to be free from unreasonable searches and seizures. It may be permissible to suspend some rights temporarily in a state of emergency -- as in a formal declaration of war by Congress -- but so far this hasn't been done.

Yet Americans don't have a constitutional right to complete privacy if it endangers the lives of others. We shouldn't deny investigators access to potentially critical information gained by foreign intelligence sources merely because the methods used to obtain that information don't conform to constitutional standards. Nor should we risk exposing sensitive intelligence information on terrorists in open court proceedings.

The administration's anti-terrorism package, for the most part, strikes the right balance between privacy and security. It would update wiretapping laws to conform to changing technologies, permit information-sharing between law-enforcement and intelligence agencies, and keep classified information from leaking in court. It would also let the government detain non-Americans deemed a threat to national security.

The proposal is not perfect. For example, time limits should be placed on the detention of foreigners with suspected terrorist ties. And we need to ensure that information collected on U.S. citizens in the conduct of a security-related investigation isn't leaked or shared with anyone inside or outside of government who has no need or right to see it.

But we must realize the nature of the terrorist threat, and our laws must change to deal with it.

As we all attempt to sort through the competing claims and emotions that confront us, we should keep one undeniable fact foremost in our minds: Civil liberties are in greater danger from a "business as usual" attitude than they are from the minor changes proposed in the administration's anti-terrorist package.

To understand why, imagine what would happen if the war on terrorism fails. Repeated attacks would create panic, and a terrible crackdown on civil liberties would ensue. As the casualty toll grew, the calls for draconian measures would make the rather modest provisions in the administration's anti-terrorist package pale by comparison. Over time, fear and loathing -- particularly if America fell victim to an attack from chemical, biological or nuclear weapons -- would create a tremendous demand to restrict liberties in the name of security.

To prevent this, we must act quickly and decisively in the short run in order to protect Americans' constitutional liberties in the long run.

This means the foreign campaign must be as broad as necessary to ensure that the threat of terrorism isn't merely contained, but defeated. If the international effort merely strikes at one man, one group or network of terrorists without fundamentally altering the policies of the regimes that protect them, another terrorist leader, group or network will arise in its place. The more forceful and effective the foreign anti-terrorist campaign, the less pressure there will be against civil liberties at home.

Americans will never be free so long as terrorists threaten our homeland. It would be ironic indeed if an inordinate fear of losing some rights were enough to deny the nation the tools it needs to stop the very thing that would doom the Constitution -- the scourge of terrorism.

Kim R. Holmes is Vice President of Foreign and Defense Policy Studies and Director of the Kathryn and Shelby Cullom Davis Institute for International Studies at The Heritage Foundation, where Edwin Meese III is the Ronald Reagan distinguished fellow in public policy and chairman of the Center for Legal and Judicial Studies.