If you’ve suspected lately that your family’s mobile-phone bill is driven entirely by your 15-year-old, you are probably right. A recent Nielsen report shows that children ages 13 to 17 average an astonishing 3,417 text messages a month — some 45 percent of all text messages. This breaks down to seven texts “every waking hour,” or roughly one every 8 1/2 minutes.

But those who look at this data and worry that young people are over-texting may be asking the wrong question. The more pertinent concern may be not the amount but the function. Many observers argue that the social world of teenagers and even young adults is nowadays largely constituted by text messaging.

Maybe so. Certainly a principal reason cited by many teens for their use of texting is that it is fun. In some surveys, young people reported that they prefer texting to conversation. And “prefer” may be too weak a word. Many young people, when not allowed to text, become anxious and jittery.

In recent years, there has been no shortage of reports on television about researchers who say they have found teens addicted to their mobile phones. Perhaps a better way to view the data is as an illustration of how mobile phones in general, and texting in particular, have taken over the experiential world of the young. An economist might expect that teens deprived of texting would simply substitute another method of communication — talking, for instance. As it turns out, a significant minority will not. They will behave instead, researchers report, the way people do when deprive d of human contact.

The phone, in other words, is not merely a tool through which teens keep in touch with friends. It is the technology that defines their social circle. If they cannot text someone, that person may as well not exist.

I’m not criticizing the technology itself. Like most people of all ages these days, I find texting far too convenient to ignore.

The trouble is that texting arose suddenly, not gradually: Originally included in mobile phones as a tool to enable service providers to spam their customers, it actually came to the United States later than most of the industrialized world. David Mercer, in his 2006 book “The Telephone: The Life Story of a Technology,” suggests that its popularity rose sharply when viewers were urged to text their votes for the winner on such television programs as “American Idol.”

This break from past practice was so radical that adults had no opportunity to work out from their own experience reasonable bounds for the young. And so the young freely created their own world, from which the old are largely excluded.

Fears of what young people might be like if left free to design the world have long been with us: Think “Lord of the Flies,” “A Clockwork Orange” or “Children of the Corn.” I don’t believe that over-texting will create dangerous psychopaths. But it might create something else.

Heavy texting has been linked to sleep deprivation among the young, evidently because they somehow feel compelled to respond, even in the middle of the night. Researchers have found correlations between texting and everything from illiteracy to overeating. A 2006 study by James Katz of Rutgers University, perhaps the leading academic expert on mobile-phone use, has found that young people have trouble giving up their phones, even for a short time. Most were unable to make it through a two-day experiment designed to discover what they would do without their phones.

On the other hand, if used in moderation, texting might help demolish the weird and unmannerly etiquette of the mobile phone, in which, for no reason but the technology’s existence, it is the recipient of the call who is somehow required to make an excuse if not free to answer. Texting harks back to an earlier, less demanding model of communication, in which response was at the convenience of the respondent. It was, and is, known as letter writing.

There may actually be advantages in the use of phones for a purpose other than conversation. The proliferation of phone apps may help children learn. And for those who are worried that constant mobile-phone use might lead to cancer, texting, in which the phone is nowhere near the ear, is obviously an improvement.

The larger problem with texting involves neither the physical nor the mental health of our growing army of young texters. My worry is that the ubiquity of texting may accelerate the decline of what our struggling democracy most needs: independent thought. Indeed, as texting crowds out other activities, it must inevitably crowd out inactivity — and there lies a danger. For inactivity and thinking are inextricably linked.

By inactivity, I mean doing nothing that occupies the mind: time spent in reflection. Bertrand Russell wrote a marvelous essay on this subject, titled “In Praise of Idleness,” noting that when the rest of the world thinks we are idle, the brain, if properly trained, is following its own path. Only then, he contends, are we truly thinking. The rest of the time we are analyzing and react ing, our thoughts determined by responses to others. Unless we spend time in reflection — in idleness — we can never truly think thoughts of our own.

Whether in the storms of political argument or the hyperkinetic workplace, we are called upon constantly to respond rather than reflect. The education of the young, increasingly built around the rapid-fire model of the standardized test, only enhances the model of thought in which speed is everything and reflection is for those left behind.

Today’s public debates are dominated by the short and the snappy, and influential pundits often seem to take pride in the assumption that nobody who disagrees with them can possibly have anything useful to say. As Cass Sunstein points out in his splendid book “Republic.com,” a crucial aspect of free speech is that it forces us occasionally to encounter a voice we do not expect to hear making a point we have not considered.

We are spiraling rapidly away from that healthy democratic vision. The explosion of text messaging is certainly not a cause of the unhealthy political world we adults are bequeathing to our children. But it points to how far we are from a cure.

Stephen L. Carter is a Bloomberg View columnist and a professor of law at Yale University. He is the author of “The Violence of Peace: America’s Wars in the Age of Obama,” and his next novel, “The Impeachment of Abraham Lincoln,” will be published in July.