Abstract
While it may remain difficult for the student of modernity to understand the weight of Paley’s teleological arguments for nineteenth century British scientists, the idea of a design in nature and the implication of a designer nevertheless provided lasting explanatory power amongst competing hypotheses until up to Darwin. As Richard Dawkins points out, it was reasonable for English scientists to maintain telic 'causes' in the explanation of biological origins until the observations of Paley were ascribed to a natural mechanism as evidenced by Charles Darwin. When viewed in the light of contemporary debates on the possibility of evolution by natural selection in opposition to purposeful intervention, it is useful, then, to understand clearly why not long ago scientists moved away from this very line of reasoning to accepting the Darwinian picture of “descent with modification” by natural selection. As Bacon was right to point out, the scientific dialogue is dependent on an agreement on method, and this change in reasoning, it seems fair to say, signifies a most important distinction of biological investigation between the nineteenth and twentieth centuries that ought not to be neglected by any thoughtful historian of science.