Editor's note: Bob Greene is a bestselling author whose new book is "Late Edition: A Love Story."
(CNN) -- How safe would you feel if:
There were no metal detectors or security checkpoints at U.S. airports, and anyone who wanted to could stroll straight to the gate and onto a flight?
People had open access to all courthouses and government buildings, state and federal, and could walk in and out without going through any screening process?
High-rise office buildings did not require the people who worked there to carry ID, and no one was stopped or asked what their business was on the way to the elevators?
Security cameras as a part of everyday life did not exist; people could walk down the street or into stores knowing that there would be no photographic or video record of them ever having been there?
People could purchase airline tickets without providing proof of who they really were?
At airports all across the country, outdoor observation decks were provided within feet of the runways, and members of the public were invited to stand on them to watch as the planes took off, with no one in authority present, and no one checking the contents of whatever packages or bags the people carried onto the deck?
Would that make you at all nervous?
For a very long time, it didn't make Americans nervous at all. That was the standard way of life. It didn't seem odd. What would have seemed odd -- what might have caused outrage -- is the way we live now.
It's something to keep in mind in the wake of the failed car bomb attack in Times Square, and the subsequent arrest of a suspect as he was about to fly out of the country. With all the talk about the ways in which security measures worked, and about how they came close to failing to work, one thing is being left out:
For all of our technologically sophisticated attempts to protect ourselves, there is a nagging feeling that we are not particularly safe. Yet only relatively recently in American social history did we feel the need to start acting with such caution. American society was, in hindsight, astonishingly open and unfettered before the final third of the 20th century. The doors were, symbolically, kept unlocked. Fear was not a growth industry.
There are any number of reasons for why all this changed. People who would harm others or create chaos figured out ways to do it using the country's air transportation system.
International travel, once a daunting prospect, became fast and easy. As criminals, both domestic and foreign, devised new ways to hurt their victims, a rapidly growing security industry matched them with innovative methods of protection. It became a zero-sum game; those who were out to cause heartache kept upping the ante, and were met with heightened levels of surveillance.
And if the zero-sum game is one that, given the choice, we never would have elected to enter. . . well, it wasn't up to us, and we're in it now. If it were a game instead of the incremental alteration of our way of life, it would feel as if some unseen crowd was encouraging us with a constant chant: "DEE-fense! DEE-fense! DEE-fense!"
But what is energizing on the athletic field -- the systematic shutdown of the opposing side's attempts to prevail -- becomes exhausting in real life. We know that all the new measures of guardedness are necessary; no one is proposing that they be rolled back. The courthouse lobbies you could waltz right through, the airports that were open to wander around in, the city streets that had no cameras aiming downward at pedestrians -- if they were to magically return to the United States, the government officials who allowed the return to happen would be voted out of office. We're accustomed to life as lockdown now; we not only accept it, but we depend on it.
Yet perhaps it is helpful to pause, if only once in a while, to ask ourselves the most basic question:
What went wrong?
Something did. If a totalitarian government had declared war on the United States, had somehow triumphed, and had instituted the measures we have levied upon ourselves -- the ID cards, the checkpoints, the cameras that never let us out of sight -- there might be an uprising. We wouldn't put up with it.
But we do, and especially at moments like the one when the suspect in the Times Square attempt is arrested we're grateful for the new tools of detection.
In the end, all of this will not be a question solely for law enforcement officials or technology experts or counterterrorism operatives. They will deal with the breaking-news aspects: the individual threats, the attacks that happen and the attacks that are stopped.
Centuries from now, though, the gradual transformation of the texture of American life -- the shift from fairly open to always on alert -- will be a subject for philosophers and social historians to explore and explain. It's not a matter of whether our unblinking vigilance is needed. It is.
Yet there has been a price, one that has nothing to do with money. And we have just begun to tally it up. The people who would bring violence upon us will devise new ways to attempt it; we, in turn, will erect newer and more intrusive barriers. The pendulum is never going to swing back. This is how life feels now.
The opinions expressed in this commentary are solely those of Bob Greene.