By Nancy Marie Brown

What does it mean to have a face? To be able to smile, to wink, to sneer? Questions like these haunt Dr. Joseph Rosen, a plastic surgeon at Dartmouth Medical School. Rosen has seen lots of patients who have lost their faces: a soldier struck by a homemade bomb in Iraq; a hunter in the path of a friend's shotgun blast; a patient with sinus cancer; a 12-year-old African boy infected by a flesh-eating form of gangrene that begins as a simple ulcer in the mouth. Not only has Rosen met these faceless people, but he has done his best to repair the damage that disease or injury inflicted on them.

Fashioning an entire nose and lips and cheeks—from belly fat, a bit of bone from an arm or a rib, a flap of skin from the forehead—is a far cry from doing nose jobs for socialites. But Rosen does tummy tucks and facelifts, too. They're good practice for his other work, repairing multiple, devastating injuries. Not only do Rosen's 500 plastic surgery patients a year help him hone his surgical skills, they get him thinking about the relationship between soul and skin.

"My original major in college was philosophy," says Rosen, who came to Dartmouth in 1991 from Stanford and is now a professor of surgery and an adjunct associate professor of engineering. "Whenever I look at a problem, I look at it through the lens of philosophy. Plastic surgery is about applying philosophical principles to the body."

For instance, what does it mean to be human? Can a body without eyes, nose, or mouth still relate to other people? What about a body without arms or legs? "After the Civil War this was a huge problem," says Rosen, who uses history to introduce students at Dartmouth's Thayer School of Engineering to problems in medicine. There were 80,000 amputees after the War Between the States ended. "When a soldier came home from the war without an arm, he didn't know if the woman he loved would still marry him," Rosen says.

He is fond of a short story written a few decades after the Civil War; the protagonist is a doctor who has lost both arms and both legs and thus his independence as well as his profession. To Rosen, the story is eerily prescient: soldiers today are coming home from Iraq with catastrophic injuries just like that. "Predicting the future is basically understanding the past," he says.

In the 16th century, Dr. Ambroise Paré, a French surgeon, wrote a book called On Monsters and Marvels. It was about people maimed in war or born with congenital defects—people who seemed almost inhuman, like a Cyclops. This was just as Europeans saw their first rhinoceroses and giraffes and as doctors began to study the tails of fetuses.

"They had no concept of embryology," Rosen says. "It was a huge challenge to make sense of it all and to balance these monsters and marvels with their ideas of God." The fact that a normal human fetus grows and then loses a tail would have been an immense surprise to Paré, as would the idea that a soldier with no limbs could live an independent life.

Today, Rosen tries to put himself in Paré's shoes and wonders what modern scientists are overlooking. "There's a space out there where surprise comes from," he explains. "I want to discover what we're not seeing that is going to surprise us. I want to ask the pesky questions. The key is to ask the questions, not to know the answers."