You could be anywhere when you hear the thunk. Maybe you're on the computer, fussing with some spreadsheets, or scanning the Sunday paper, or pouring yourself a delicately calibrated cocktail—whatever it is, it requires concentration. Which is why your child—your beloved, your joy, the carrier of the genetic blueprint of your essential youness—is in the care of someone you're supposed to trust. Namely, your wife. And this is what makes the thunk so complicated, so...confusing. It's loud. It's sudden. It reverberates through the house like the sound of a bowling ball being dropped from 25 feet and smacking into an anvil. And the thunk is followed, after a few seconds of ominous silence, by a shrieking and howling and gibbering that would send a chill down the titanium spine of the Terminator. The individual who is shrieking is, of course, your child—your beloved, your joy—whose cranium has just introduced itself to the hardwood floor after the unfortunate toppling of a high chair. And at this moment a thought races furiously through your mind....

...Well, now, do we even want to admit that in public? Because the thought that races through your mind is unspeakable, really. It's the sort of deeply buried misogynist murmur that, had you said it out loud back in the early nineties, might have gotten you expelled from college. When you hear the thunk, you think: My wife is a bad mommy. Yes, you do. You're well aware that accidents can happen in the presence of anyone (you, for instance), and you know in your marrow that rampantly blaming your partner is a recipe for marital and karmic disaster, but still, you can't quite stanch the underground torrent of spite, a subconscious rumble that makes you wonder if she's actually, um, gulp, up to the job.

The thunk is not the only mishap that can release this outlaw idea from its bone-strewn dungeon. There is the junk-food flinch: Oh, wow, so Max is having hot dogs and Cheez Nips for dinner again, eh? For the seventh day in a row? There is the hacking-cough conundrum: Okay, but if you knew that Alexandra had bronchitis, why did you invite her over for a playdate? And let us not forget the crunched-thumb enigma: In my own experience, honey, I have found that it's better to slam the car door after Jeremiah has removed his hand from the vicinity.

Will you ever say any of these things? No. This would mean conveying to your wife that she is the shittiest care provider since Medea, and divorce lawyers are said to be very expensive. In America, at least, these inaugural years of the 21st century are marked by a harried fixation on perfect parenting. A bourgeois breeder comes off as an irresponsible deviant if he or she fails to shell out thousands of clams for the "right" stroller, the "right" crib, and the "right" car seat. To suggest that your lawfully wedded is guilty of outright negligence—or at least complete cluelessness regarding the laws of physics and the basic principles of nutrition—is to say pretty much The Worst Thing That Can Possibly Be Said.

True, some women might like to be called "bad mommy" in a bedroom game involving safe words and vinyl tubing. (Sorry, I swore I wasn't going to make this about me.) But by and large the phrase has very unpleasant connotations. Mommie Dearest. Susan Smith. Besides, a lot of women already feel guiltier than Scott Peterson for spending so much time at the office. Yep, the modern mommy is doing just as much as you are to bring home the braised pork belly: She works. Which means that her brain is elsewhere, and that makes her feel anxious enough. Today a bad mommy is not necessarily the woman who plows through a bottle of Bailey's Irish Cream while letting little Justin spend the whole afternoon up the block with the retired scoutmaster who collects clown paintings. She may be the frenzied working mother who wants to organize her children around her career, without a whole lot of sensitivity to their needs and schedule. She may, in fact, look a lot like the joint-custody deadbeat dads of yore, scheduling an hour of quality time with her kids every Tuesday and Saturday.

My brother works on the road most days but tries to arrange his schedule around what is happening with his children. "If Hal has a meltdown and needs some quiet time, I'll say, 'Fuck it, we're not going to dinner. We go to enough dinners,'" he says. "Lydia puts too much priority on work—some clients from Silicon Valley are suddenly the most important thing in the world. But they're not. They're clients. Lydia is a bad mom when she tries to do too much: work, cook dinner, go to Tess's volleyball game, and take a conference call. But that's just the nature of our lives."

For any father who spends more time with the kids than his wife does, the "bad mommy" charge is the nuclear option. It's the button you don't want to push, and there are several reasons for that—reasons that go beyond a terror of the word alimony. For one thing, you suspect that these passing clouds of male chauvinism are nothing more than remnants of a pre-enlightenment epoch—sort of like your leftover Henry VIII reflex. Your wife is, in fact, a terrific parent! Just take a look around at those hillocks of Happy Alphabet! flash cards—she and little Jack spend hours with those! Or remember the time she coaxed Cornelius into eating an entire bowl of edamame, or consider how gracious and forgiving she was when you were bathing Cassandra and forgot to test the water temperature, oblivious to the curls of steam skating on the surface....

...Yes. There it is. If there is one central reason why you will never speak up about the thunk, it's because you know that you are in no way exempt. Every man stands one wobbly booster seat away from becoming the fuckup father. In fact, a principle of instant karma seems to govern the enterprise of parenting. Scowl when your wife lets your toddler trip on the carpet and you will be the one who accidentally conks him over the head with a bottle of olive oil. Snicker that the kid's been watching too much tube and you will be the one who forgets to fast-forward past the scene where Bambi's mother is brutally gunned down. There's something to be said for the benign-neglect school of parenting, as my friend Peter likes to point out, and yet he is brave enough to admit that his approach recently put him in a bizarre and not-quite-benign predicament: His son Hugh got his head stuck in a cat carrier. "I had visions of us taking a cab to St. Luke's hospital with Hugh wearing a cat box," Peter says. "We finally wrestled him out of it." A good thing, too. If there's anything worse than hearing the thunk, it's hearing two words that Dr. Seuss might have used in a twisted rhyme: bad dad.

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