The Meaning of Life

Carl Zimmer over at Seed Magazine:

It's hard to think of a word more charged with meaning—or meanings—than "life." Some of the most passionate debates of our day, over stem cells or the right to die, genetically modified food, or wartime conduct, revolve around it. Whether we're talking about when life begins or when it ends, the sanctity of life, or the danger of playing God, we all have an idea of what we mean when we talk about life. Yet, it often turns out, we actually mean different things. Scientists, despite their intimacy with the subject, aren't exempt from this confusion.

"There is no one definition that we agree upon," says Radu Popa, geobiologist and the author of Between Probability and Necessity: Searching for the Definition and Origin of Life. In the course of researching his book, Popa started collecting definitions that have appeared in the scientific literature. He eventually lost count. "I've found at least three hundred, maybe four hundred definitions," he says.