Biologist Ernst Mayr says that Darwin's great contribution is to introduce into biology a new way of thinking, "population thinking." Since then, you find the phrase in many literatures on biology. According to him, it replaced typological thinking which he assumes to be based on essentialism. However Elliott Sober criticizes him for his misunderstanding of Darwin's innovation. First, I summarize Mayr's characterization of population thinking and then survey Sober's criticism. Sober says that population thinking doesn't clash with typological thinking but with Aristotle's model of essentialism which Sober calls "natural state model." Next, in order to clarify the nature of population thinking, I describe how population thinking has emerged. After Darwin, many authors, especially Francis Galton and Ronald Fisher, mathematize evolutionary theory. They change the concept of population, and a new way of thinking about normality emerges. Finally, I discuss what population thinking really brings about and argue that population thinking nowadays is essential to biology and other sciences.

特集 : 西脇与作君・樽井正義君退職記念
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