Nigel snaps a couple of photos.

I try distancing myself. Where would I place this on the spectrum of humiliating episodes in my life? Probably better than the time I inadvertently drooled on the piano during music class in sixth grade and Kim Glickman pointed it out to everyone. But worse than the time I asked my wife Julie's friend when she was due (her baby was six weeks old).

"Okay, now," says Nigel. "Sook in yer goot!"

I stare at him blankly.

"Sook in yer goot!"

My goot? Nigel taps his stomach.

Ah, he's talking about my problematic belly. I sook in some air.

Nigel begins snapping photos. The Frisbee-sized lights flash, making a soft pop, like a snare drum in smooth jazz. I sit. I try to think dignified thoughts. Think of the Romans, the Greeks. They posed nude and still started civilization as we know it.

I feel vulnerable, yes. There I am, exposed for all to see. But paradoxically, I feel disappointed that no one seems to be looking at me. Nigel has a cadre of cute, young female assistants. They are busy making cell-phone calls, chatting about what they heard on NPR that morning, unpacking lenses. My nude form holds about as much allure to them as a wicker chair.

I adjust my pose, lowering my knee. Nigel raises his eyebrows.

"Not like that. I can see your chopper," he says.

I move my knee fast. I don't want my "chopper" on film. I'd spent the previous three days worrying about its debut in public. I became irrationally obsessed with the idea that it might misbehave.

I don't want my "chopper" on film.

Which is highly unlikely. It's not like I'm thirteen. But what if it does? Stress can do strange things to the body. And if it does, I'd never live it down. I'm terrified of losing control in any situation, and this would seem to be the worst. So I took measures. I've brought along a small black-and-white photo of my late grandmother just in case.

"Your poor grandmother," Julie said, as I scoured photo albums for the picture the last night.

I've read interviews where celebrities claim to have felt empowered by their nude photo shoot. They learned to embrace the freedom and love their body and throw off the constraining shackles of repressed society. Not me.

I just don't feel comfortable nude. Even when I'm alone in my apartment, I keep my pants zipped. No doubt this comes in part from my ambivalence to my physical self. Maybe it's a Jewish thing — never has a race of people been so disassociated from their bodies. Like many Jews, I spent a lot of my life viewing my body as a way to transport my intellect from place to place. In my twenties, I had a brief half-year fling with weight lifting and StairMaster (guess what? I was single at the time!), but other than that, I haven't logged a lot of hours at Bally Total Fitness. And it shows. My chest has an indentation where you could store a half cup of flour.

I'm much more comfortable exposing the contents of my mind — even when those contents are potentially more humiliating than my chopper. I'll expose my ignorance long before I take off my t‑shirt.

My sons, incidentally, don't have the same problem with bodily repression. Zane, for instance, loves to get nude. A few months ago, I was on a book tour stop in Cincinnati. I had a prearranged video chat with Julie and Zane. I was on wireless at Starbucks and called them up on my Mac laptop. Julie put the camera on Zane.

And Zane decided, at that moment, that his clothes were restraining, and whipped off his shirt and pants.

I chuckled. Until I started to figure out how this might appear: a thirty-nine-year-old man watching a naked toddler cavort on his computer screen. I glanced around to make sure no one was calling the authorities.