Probably every new parent can identify with the feelings Brian Castner expressed in the Daily Beast this weekend: "a father’s concern for his children’s safety—a panic over the helplessness of a baby so small it could stop breathing at any moment."

Castner, however, feels that panic more intensely than most of us, having served as a bomb technician in Iraq and seen (as he says) many disturbing things. He wrote a memoir of that service and of his homecoming after, in which he described how he dealt with his fears: "sitting outside my newborn son’s room all night with a gun so that no one will harm him, and practicing reloading my pistol one handed so I could defend my children while driving them to school."

One can honor Castner's service - and feel compassion for the bad memories he carries with him - while also thinking: "Friend, you are behaving not only irrationally, but dangerously. In your aspiration to protect your son, you are exposing him to vastly greater risks."

Castner quotes an exchange he had with Terry Gross on NPR's Fresh Air:

Gross: I want to describe something you write that I found very disturbing. . . You describe wanting to strap a pistol to the center console of the minivan. And I thought that’s just, that’s scary. I mean you have kids, who’d be driving in that family minivan.

Me: Well, I can understand how you would call it scary because my children were there. [But] that's why I wanted it because I needed to protect them. . . . I had seen so many dismembered children in Iraq that I, as a father, I really felt the need to protect them from something and this was how I knew to do it.

In the US, however, the greatest risk to children comes not from roadside IEDs, but from carelessly handled handguns belonging to the loving adults in their lives. About 600 children per year die in gun accidents, and many more suffer wounds and shock in non-lethal accidents like this one that occurred in Idaho last week:

Officials in Canyon County say a 3-year-old accidentally shot a baby in the face with a loaded handgun found in a car.

County public information officer Joe Decker says the 3-year-old and a 10-month-old were left unattended in a vehicle at the family's home Monday afternoon when the older child found a gun and unintentionally fired it, hitting the baby in the cheek.

Human beings are notoriously poor estimators of risk. We are phobic about flying, but not about driving - although driving is vastly more dangerous. We buy shares when the market has crested, and sell when the market has hit bottom. And we hope to protect our children by laying a loaded gun in a bedside table - where it is hugely more likely to cause a tragic accident than ever to stop an intruder.

Castner acknowledges that, in the end, he reasoned his way to the right answer: no gun in the minivan. Yet it's plain that he thinks a little worse of himself for allowing his judgment to overmaster his unreasoning dread. He introduces to a concept from the concealed-carry world that divides Americans into three classes: "wolves" (criminals and other predators); "sheep" (those who don't keep guns in the home); and heroic "sheepdogs": those who, by carrying guns, protect all the rest of us. Well, thanks. But you know, there are a lot of happy little Pomeranians out there who may believe themselves sheepdogs, but who would prove worse than useless in any serious trouble. What procedures should we put in place to train and identify these noble protectors of us weak sheep? Answer: zero. "Sheepdogs by definition choose themselves."

Ah. But the trouble is that for every valiant grandmother who protects home and hearth with her trusty shotgun, there is at least one trigger-happy George Zimmerman cruising the streets looking for a fight. For every properly trained veteran diligently securing his weapon, there seem to be dozens of people who are leaving loaded firearms out for children to find and fire.

If there's one key concept that inspires the champions of the gun status quo, it is this claim that gun owners can be neatly divided into two classes: bad and good. The good owners are not only well-intentioned, but are also presumed to be competent, responsible, sober.

But in the real world, human beings spread themselves along much longer gradients of behavior. Some are well-intentioned but careless. Some are admirably well-tempered, except when they have had too much to drink. Some would never hurt anybody except their ex-girlfriend. Some are skittish and trigger-happy. Some are just plain bad shots, who would with 7 bullets hit every person at the crime scene except the criminal. And all of them, in Castner's telling, are entitled to nominate themselves as protectors of society.

Of course, the vast majority of people who carry legal weapons will never draw them in a situation of danger. If their guns are ever used, it is because they have been stolen by a burglar who targeted their home precisely in order to get hold of their guns - or in the suicide of a depressed relative - or in some stupid dispute that they themselves start because emboldened by a gun - or in some heart-rending accident.

It is only after the fact, and tragically often, that we discover that the greatest threat to our family came from our own poorly conceived yearning to protect them.