Spinoza said that all things wish to continue in their own form forever: the human desire to live longer is instinctive. And we're getting better at it. The life expectancy of a person born in the United States in 1900 was 47 years; for a baby in 2002, it was 77 years and a few months. This remarkable improvement is due to a century of medical advances, particularly those involving the treatment of severe infections, traumatic injuries, and certain contagious diseases. But average life expectancy has risen extremely gradually in the last 50 years. Using conventional medicine, human beings in wealthy nations seem to be living about as long as they can.

This is because we haven't cured aging or the diseases of aging. Even if you stay healthy most of your life -- avoiding car accidents, various fatal infections, and any number of deadly ailments -- your body will age and die. But is the aging process biologically immutable? That's the question raised in this month's profile of Aubrey de Grey, a University of Cambridge computer scientist and self-taught biologist who loudly and angrily argues that there is nothing inevitable about aging and death (see "Do you Want to Live Forever?"). Aging, he says, is "repulsive" and death from aging "barbaric." De Grey, who lectures and publishes widely on the topic, claims that by "perturbing" our cellular processes, we could live for thousands and thousands of years. Further, he says that we will be able to do this 25 to 100 years from now.