 Much debate over the role of teleology in biology in the twentieth century, especially amongst the architects of the ‘modern synthesis’, traces back to Charles Darwin’s theory of evolution by natural selection. Biologist and philosopher Michael Ghiselin, expressing a common interpretation of Darwin’s role in this debate, claims in his preface to Darwin’s work on orchids that Darwin’s theory succeeded in “getting rid of teleology and replacing it with a new way of thinking about adaptation” (Darwin 1862/1877 [1984: xiii] cited in Lennox 1993: 409). On this view, the theory of natural selection explains how species “have been modified so as to acquire that perfection of structure and co-adaptation” without any appeal to a benevolent Creator (Darwin 1859: 3). Prior to Darwin, the best explanation for biological adaptation was the argument from design, most influentially presented in William Paley’s Natural Theology (Paley 1802): living things have the structure and behaviors that they do because they were designed for certain purposes by a benevolent Creator (see the entry on natural theology and natural religion). Darwin’s theory provides biology with the resources to resist this argument, offering a fully naturalized explanation for adaptation. Although most agree that Darwin’s theory does indeed purge evolutionary biology of any illicit appeal to external, Platonic teleology, there is disagreement as to whether or not Darwin’s evolutionary explanations are teleological (see the relevant section of the entry on  Darwinism).  Even Darwin’s contemporaries disagreed as to whether or not the theory of natural selection purged teleological explanations from biology or revived them (Lennox 2010). In any case, it is clear that Darwin used the language of ‘final causes’ to describe the function of biological parts in his Species Notebooks and throughout his life; he also reflected frequently about the relationship between natural selection and teleology (Lennox 1993). 