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.

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