In Oscar Wilde's novel, "The Picture of Dorian Gray," the main character barters his soul for eternal youth but becomes wicked and immoral in the process.

Leon Kass believes humanity risks striking a similar Faustian bargain if it pursues technology that extends life spans beyond what is natural.

If our species ever does unlock the secrets of aging and learns to live forever, we might not lose our souls, but, like Dorian, we will no longer be human either, says Kass, a bioethicist at the University of Chicago and a longtime critic of life-extension research. For Kass, to argue that life is better without death is to argue "that human life would be better being something other than human."

Kass' position is controversial, but it gets at some of the central issues surrounding the life extension debate: What is aging? Is it a disease to be cured or a natural part of life? If natural, is it necessarily good for us?

Virtues of mortality

In numerous presentations and papers throughout the years, Kass has argued for what he calls the "virtues of mortality." First among them is the effect mortality has on our interest in and engagement with life. To number our days, Kass contends, "is the condition for making them count and for treasuring and appreciating all that life brings."

Kass also believes that the process of aging itself is important because it helps us make sense of our lives.

A 2003 staff working paper drawn up by the U.S. President’s Council of Bioethics—then headed by Kass—states: "The very experience of spending a life, and of becoming spent in doing so contributes to our sense of accomplishment and commitment, and to our sense of the meaningfulness of the passage of time, and of our passage through it."

Technology that retards aging, the report argues, would "sever age from the moorings of nature, time and maturity."

Reality sets in

Daniel Callahan of the Hastings Center, a bioethics research institute in New York, agrees that the pursuit of extension technology is unwise, but thinks Kass' views are too extreme.

"His view is that the fact that we're going to die makes us think more seriously about our life," Callahan said. "I don't know if that's necessarily true. I'm 75 now, and that certainly hasn't been my experience."

Callahan also questions the idea that our humanity is somehow tied to our sense of finitude.

"I don't think one can make our humanity dependent on the length of our life," Callahan told Livescience. "Even if we live to be 500, we'll still be human beings."

Besides, other critics say, Kass is primarily concerned with immortality, something that most scientists say will never happen. "There is no research into extending the life span thousands of years," said Richard Miller, a pathologist at the University of Michigan. "That's fantasy."

Even when applied to the more modest and realistic goal of extending our life spans by a few years or decades, or even doubling it, Kass' arguments don't hold up, said Chris Hackler, head of the Division of Medical Humanities at the University of Arkansas.

"We live [longer now] than we did a century ago but that doesn’t mean we take life any less seriously or less creatively, so I don’t know why projecting that for a doubled lifespan would be radically different," Hackler said in a recent telephone interview.

Hackler also points out that even if people could potentially live to be 180, they could still die from accidents or disease: It is not the knowledge that we will die by some certain age that spurs us to make the most of life, Hackler says, but the awareness that we can die at any moment—and that will not change even if we are immortal.

Eternal bore

Instead of worrying about what longer life will do to our sense of humanity, Callahan and Hackler wonder what the heck people are going to do with all their extra time. Longer life means more time for boredom to creep in.

"Let’s face it, most peoples' jobs aren’t all that fascinating," Hackler said. "They put in a 9-to-5 and they’re glad to have the weekend. So you wonder if having twice as much of this is a good thing, or if you’d get totally burned out."

Hackler can't imagine himself ever getting tired of living, but he knows not everyone will feel same way. Determining how much ennui the average person can bear will be important if life extension ever becomes a reality, Hackler says, because extended boredom could result in prolonged unhappiness or higher incidences of suicide.

Against concerns of chronic boredom, those in favor of extending life spans significantly say, "speak for yourself." Aubrey de Grey from the University of Cambridge believes longer life will invigorate people to do the things they've always wanted to do. "There are things that no one attempts today because they feel they'll never get them done in a lifetime," de Grey writes. "If a lifetime is a lot longer they'll try them."

Callahan thinks this kind of thinking gives the average person too much credit.

"I don't believe that if you give most people longer lives, even in better health, they are going to find new opportunities and new initiatives," Callahan has said. "They will want to come and play more golf maybe, but they aren't going to contribute lots of brand new ideas, at least the ones I know."

Moderation

Even if people had all the time in the world, they will never be able to do all the things they wanted to do, Callahan argues.

"Even if you've seen everything, you might say 'Well, I want to go see India once again,'" he told LiveScience. "It seems there's a possibly never-ending cycle there."

If people end up doing most of the things on their to-do lists by the time they reach 80, then perhaps that is good enough.

"The fact that there are still some countries that I've never been to does not ruin my life," Callahan said. "I've never been to Nepal or Antarctica but it's hard to work that up to some great tragedy of my life."