We don't know what life is ... (Zimmer)

I thought biologists had a working definition of "life", albeit with a bit of fuzziness. Ok, so that's what I'm remembering from my high school biology, but that was less than 237 years ago.

Carl Zimmer tells me I'm quite mistaken ...

Zimmer: The Meaning of Life

...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.

It's a peculiar state of affairs—biologists have learned more in the past decade about how living things work than we've learned collectively over the past several centuries—and an intense debate has arisen over what to do about it. Some are skeptical of science's ability to come up with a definition of life that's accurate enough to be meaningful, while others believe a definition is not just possible but essential for the future of biology.

"A science in which the most important object has no definition—that's absolutely unacceptable," says Popa. "How are we going to discuss it if you believe the definition of life has something to do with DNA and I think it has something to do with dynamic systems? We cannot have a conversation on any level. We cannot make artificial life because we cannot agree on what life is. We cannot find life on Mars because we cannot agree on what life represents."

Recently, a new voice has entered the debate. Carol Cleland, who teaches philosophy at the University of Colorado and works with NASA's National Astrobiology Institute—essentially as their philosopher-in-residence—is making a more radical argument: Scientists should simply give up looking for a definition of life. They can't even begin to understand what life really is, she claims, until they find forms of life profoundly different from those we know here on Earth. Only when we can compare alien life with life on our planet will we understand the true nature of this ubiquitous, ephemeral thing.

Cleland believes biologists need to build a theory of life, just as chemists built a theory of the elements and physicists built a theory of electromagnetism. Definitions, she argues, are concerned only with language and concepts, not true understanding. By taking the semantics seriously, Cleland is calling for nothing less than a scientific revolution. Only when we change the way we think about life, she argues, will the true study of it begin...

Once again, familiar territory to readers of the past twenty years of science fiction. I've really got to learn to trust mscience fiction writers more ...