Microscopes made possible the discovery of an amazingly complex microscopic world, and sexual reproduction in the smallest insects. English and French philosophers in the late 1600s rejected Descartes’s notion of the spontaneous emergence of life from laws of motion acting on inanimate matter. Antoine Lavoisier eventually demonstrated in the late 18th century, before his neck met the business end of a guillotine, that water was only nourishment for plants, not their source. Lavoisier was the first to describe plant and animal respiration, and his work with oxygen, respiration, and combustion became the foundation of modern chemistry, and was one of Kuhn’s examples of revolutionary, paradigm-founding work. Religious philosophy was also involved in the spontaneous-generation debate, as life coming from random processes, by mere “chance,” was directly opposed to the day’s theology. In the late 17th century, the pre-existence of souls and the seeds of life were popular ideas. wrote and was concerned with sexual reproduction, but he was rather neutral about the ultimate spontaneity of life. The issue was a chicken-or-egg argument, and the egg position prevailed at times.


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