Monday, June 26, 2006

What is Life?

Usually life is defined as a certain a set of activities or processes, such as reproduction, metabolism, irritability. But it is not too difficult to come up with examples that meet each criterion and yet which are not alive, according to common sense. Crystals grow, for example. Fire “metabolizes” fuel, grows, and reproduces itself. Rivers are irritable, in that they try to get around rocks, dams, and other obstacles placed in their path.

Just having DNA is not good enough, since I don’t want to say that a test tube full of DNA is alive. Is a virus alive? Scientists aren’t sure. If it is alive, does it stay alive when you take it apart, or is there something special about the system of parts that confers aliveness. Are gametes alive (e.g., sperm and egg cells)? Spermatazoa certainly look alive, but they do not have full complement of DNA, and can’t reproduce.

At some point, one is forced into a corner, defining life simply as those things that are alive, and the definition is totally circular. That's no good.

I don’t think there is a special “life force,” but I think the question of life must be wrongly formulated somehow.

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