"Are you OK?" The worry in my sparring partner's voice is sincere: Hard contact is one thing, but the school knows that injuries lose paying customers, and rent in Manhattan isn't cheap. In my head, though, I hear only the taunts of the football team as I asthmatically force my overweight sixteen-year-old body around the school's running track. I wipe the smear blood away from the corner of my mouth and am ready for another round of sparring.

Later that evening, after she scolds me for limping into the restaurant forty-five minutes late, my girlfriend will run her fingertips over the hen's-egg-sized bruises on my legs and attempt to massage away the knots in my shoulders. When she reaches my nipples, I will push her hand away, as her touch conjures recollections of cruel-eyed camp counselors twisting my thirteen-year-old breasts until I thought I would pass out from the pain.

My coworkers, attractive young men and women with degrees in literature from Ivy League schools and an encyclopedic knowledge of how to have fun in New York on an editor's salary, often ask me why I spend my Friday nights in a mirrored room, being yelled at in Japanese and sweating into a white cotton uniform, so unfashionable after Labor Day. According to the Village Voice and New York Times Magazine, I should be drinking mojitos in a dive bar in the East Village, complaining with my fellow writers about how hard pretentious Caucasians with expensive liberal-arts educations have it in New York City. I don't reply to their questioning, but I'm forcefully reminded of my fourteenth summer, waiting for my mother to pick me up from the orientation session for my summer-job-to-be at a day camp in my neighborhood in Brooklyn. The boys who surrounded me in front of the Hebrew Educational Society had baseball bats, but no balls or gloves. In their pockets were homemade brass knuckles and razor blades and sharpened screwdrivers. One backed me up against a street sign, questioning my reason for existing, while his friend rapped me on the back of the head with a Major League Baseball-endorsed cylinder of tooled aluminum. The same gang later beat a yeshiva student to death not far from my high school for no particular reason, and the same would have likely happened to me if a friend of mine who also knew them hadn't shouted, "leave him alone-he's just a little nerd."

When my mother arrived in the little red Hyundai hatchback, I broke down hysterically in the front seat and demanded to be allowed to start martial arts lessons immediately. It was out of the question: The only martial arts teacher they knew of was a hardware store owner who came to pick up his ten-year-old son at school armed to the teeth with folding knives and keychains that doubled as knuckledusters. He was a poor role-model for a nice middle-class Jewish kid who was destined to become a doctor or a lawyer, so instead, I was sent back to the child psychologist. My mother still has no idea of how close to dying I came that day.

For years, I replayed the scenario in my head. In my fantasies, I wrested a bat away from one of my assailants and turned it, Charles Bronson-style, on them. That was half a lifetime ago, and I've grown slightly wiser: The more likely outcome would be my mother pulling up in the evening dusk and not seeing me. She honks the horn, then, five minutes later, impatient to go home and get dinner started, risks double-parking to see if I might be in the reception area. Getting out of the car, she sees me lying in a puddle of my own blood, my face mangled so badly that she would not have recognized me if not for my L.L. Bean jacket, my teeth, and thousands of dollars in orthodontics, strewn across the concrete sidewalk.

I began training in earnest in college, somewhere between my attempt to disappear into the parallel universe of medieval romance offered by the Society for Creative Anachronism and a bout with anorexia. When I left graduate school and got a real job, though, I found that my martial pursuits made me more of a misfit than I had been growing up. Society likes it when we fit into neat categories. The college-educated, white-collar, homo cubiclis can not come into work with a black eye, or limping and exhausted from the previous night's sparring class. My supervisors and colleagues would glance nervously at the twelve-ounce gloves hanging from my backpack or the bag full of weapons lying by my desk or the gi drying in the closet. They would crack stupid Bruce Lee jokes, as if to reassure themselves that I wasn't about to whip out a samurai sword the next time they asked me to work late and miss class. Yoga, jogging, a health club membership-all this, they could understand, as it is part of the milieu of the young Manhattan professional. Contusions, on the other hand, most certainly are not.

Two men are having a fight in a bar on Second Avenue. I see the effect they have on the bystanders before I actually see the combat itself, men and women skittering away from their violent energy like water droplets on a hot frying pan. I pause on my way home and watch them through the plate-glass window, analyzing the fight as if they were on television. They embrace and stagger around the bar's vestibule, bouncing off the walls like drunken tango dancers. There are many things you can do in this situation: Snake your leg around the other man's, throw him or take him down. Take one of the arms he is using to hold you and use a joint lock or break his elbow. Cup your hands and slam them over his ears, bursting his eardrums. Cross your wrists and seize his collar and squeeze to cut off the flow of blood to his brain, and he will be unconscious on his feet in seconds. Drive your stiffened fingers into the right spot on his neck, and you will collapse his trachea. Disgusted by their amateurish violence, I walk on.

I couldn't care less about professional sports-I would bring a book to the stadium when my rather disappointed father would take the whole family out to see a ball game-but I buy a Yankees hat at Port Authority minutes before I board a bus to spend a weekend up in Massachusetts with my girlfriend, watching the leaves change color and eating organic granola. The Red Sox have just beat the Yankees in the first game of the playoffs, and the college students my girlfriend teaches at UMass-Amherst have responded by gathering the furniture in their dorms into a large pile and lighting it on fire. Her students have offended me: Education doesn't mean anything to them; it's just some place your parents send you to goof off for five or six years before you can get a real job. I walk around the UMass campus in my leather jacket, leather pants, skull-and-crossbones bowling shirt, and Yankees hat.

Nobody says anything to me. I am six-foot two and two hundred ten pounds of scowling, shaven-headed, goateed New York Jewish intellectual. In my armor, I am inviolable.