How would you like it if a police officer stopped you on the street and asked you to show your identification card? Of if you were visiting in a strange city and you had to show your I.D. card and register at the local police precinct station? Many Europeans live by such rules and take them for granted. Britain required identification cards in World War I and again in World War II, abandoned them in 1953, but now is considering them once more.

The terrorist attacks of Sept. 11 are pushing the United States in the same direction, although the cards are not part of the new terrorism bill. Recent polls show that most Americans now favor I.D. cards. Larry Ellison, the chief executive of the software maker Oracle, has given the idea a boost by suggesting a voluntary national I.D. card system that would replace existing Social Security cards and drivers’ licenses. He offered to donate the software.

Alan M. Dershowitz, a law professor at Harvard, also has proposed an optional card, much like the windshield or dashboard device that lets you drive right through a toll plaza on a bridge or turnpike and pay later. He argued in a New York Times article that people would be trading a little less anonymity for a lot more security.

In this country, national I.D. cards have always been controversial. When Social Security cards were first considered, critics warned that they would become all-purpose identification cards and would lead to a police state. Government snoops have been a specter to many, especially in the Red hunts in the 1920s, in the era of McCarthyism, and among resistors against the Vietnam War.

In South Africa’s apartheid era, the government required blacks to carry passbooks, setting forth the areas where they were allowed to live and work and simply exist. Police could stop blacks whenever they felt like it, and carrying no passbook was a criminal offense. George Orwell,

in his book “1984,” coined the term “Big Brother” for the know-all state that permitted no privacy at all.

For many, the terrorist attacks and continuing threats mean that the right to anonymity has lost its importance. Professor Dershowitz wrote: “I don’t believe we can afford to recognize such a right in this age of terrorism.” He and others argue that various identification cards have so mushroomed that anonymity is pretty well gone anyhow.

The United States has already begun what amounts to a pilot project. The Immigration and Naturalization Service is preparing 4 million cards containing fingerprints and personal information for Mexicans crossing the border frequently. Thirty-six states and the District of Columbia (but not Maine) already have or are planning drivers’ licenses that can digitally record driving records, fingerprints and photographs. And an imaging company has developed a digital process for recording and scanning eyes in the belief that irises are more definitive than fingerprints.

Some enthusiasts foresee a universal U.S. system of “smart” cards, containing all manner of personal health and genetic information as well as employment and any law-enforcement records, plus one consolidated national database.

The advantages seem obvious, but so do the drawbacks. The time has come for thorough public hearings and a national debate to explore the pros and cons and to fashion assurances that protect individual rights to be safe from illegal search and seizure and from what could amount to self-incrimination.