Life is nothing more than "chemical processes dependent upon common chemical forces."

"If prionlike diseases are infectious, though, they are not so in the traditional way. They are not "alive"-infection in their case is purely a mechanical process. The theory of prions threatens to diminish our uniqueness in the universe, which is one reason that-like Galileo's insistence that the earth moves around the sun-it had trouble finding acceptance. It was another example of-in the words of the German chemist Friedrich Wohler, who discovered in 1828 that he could synthesize the body's chemicals perfectly well in a test tube-"the great tragedy of science, the slaying of a beautiful hypothesis by an ugly fact." The hypothesis was that life is ineffable, uniquely alive; the reality is that it is just chemical. Or, as Justus von Liebig wrote in 1855, life is nothing more than "chemical processes dependent upon common chemical forces.""