Children are the fastest way to bring on a collision between reason and emotion.
If you are a parent, for example, you probably know the odds of your kids being snatched by a stranger are absurdly low.
But that little voice in the back of your head whispers names - Polly Klass, Elizabeth Smart - that in a saner world you would not know.
Yet still you toss the kids outside to play, even as you cross your fingers behind your back.
If we parents allowed emotion to overtake reason, if we curtailed children's liberties whenever our hearts fluttered, all kids would be locked in their rooms eating off sterilized cutlery and being schooled by distance learning until the age of 21.
My seventh-grade daughter's middle-school curriculum includes a routine class trip, scheduled for this week, to Washington.
But this is no routine moment in U.S. history, is it?
We parents met with school officials to discuss this trip, and began with the basics.
Good walking shoes. Rain gear. This. That.
We were deep into that meeting before anyone had the - the what? Nerve? Courage? Impatience? Well, anyway, before anyone brought up the issue of the kids' safety, that pink elephant sitting quietly in the middle of the room.
We were, after all, about to send our kids to the very heart of our nation, to its capital city, and two important elements could not be ignored: That the word “terrorism” is no longer abstract, and that this very week was starting to smell very much like war.
The more we talked about our children's safety and security, the more anxious I felt. Funny, how planning for the worst can quickly make you fear it deeply.
But once again, in that wrestling match between parental emotion and reason, reason triumphed.
On Monday, I watched the tail lights of the chartered bus carrying my child disappear into the fog that obscured Toledo that morning.
The kids were due back tomorrow. But yesterday, we parents checked e-mails and answered telephones to discover that the trip was aborting. At one o'clock this morning, we were to meet our offspring in the school parking lot.
We are, all of us Americans, just learning to live with uncertainty.
We are just beginning to understand how unnerving it can be to live without the illusion of being in complete control, which is perhaps one of the most central American characteristics.
We don't much like this new rainbow world. We far prefer the monochromatic sameness of unchanging safety and security.
As disappointed as I am to see this trip end early, I can hardly levy blame; after all, it wasn't me who was responsible for a flock of other people's very precious children.
But I'll be looking for some way to reassure my daughter that uncertainty and fear aren't always cause enough to retreat, and that sometimes, it might even be the price we pay for living in a free society.