A re-examination of Darwin's argument in On the Origin of Species
Authors:   , Grove Richard S. 
Published: February 2025

Darwin's argument for the mutability of species in the Origin is generally regarded as a successful and skillful presentation of ideas important to the biological sciences, to the history of science, to philosophy, and to natural theology. In the 110 years since its publication the book has received extensive commentary from scholars in many fields, but little intensive analysis as a work of rhetoric consciously designed to inform and to persuade a mixed group of readers. This study attempts to analyze and to evaluate the Origin as a rhetorical structure, recognizing the many persuasive aspects of the work but nevertheless questioning the validity of Darwin's argument for natural selection. In writing the Origin Darwin carried his argument to educated laymen as well as scientists. The hostile attitude of contemporary scientists seemed to preclude an impartial response to his theory, unless this narrow attitude were offset by the support of educated laymen at large. To bring his argument to educated laymen Darwin employed a common style and used familiar metaphors; further, he constructed an argument for natural selection based on the lay reader's own experience of organic nature. For the scientists among his readers, Darwin used natural selection as an hypothesis to be tested against available evidence; in addition, he showed that natural selection could become a unifying principle for a new biological synthesis. A more detailed analysis of the Origin shows that Darwin's personality--reliable, modest, impartial yet enthusiastic about the discovery of natural selection--adds greatly to the weight of his argument and favorably disposes the reader to Darwin's evidence and his vision of organic nature. Darwin arranges his evidence so as to give the reader an increasing awareness of natural selection. By carefully noting the effect of accumulative selection on organic nature, the reader discovers the powerful action of natural selection. To help the reader see the evidence from the proper viewpoint, Darwin employs a panoramic historical view, an accelerated depiction of organic change, and the precise detail of close-up vision; when combined, these viewpoints make evolution visible to the reader. Finally, to his control of evidence and viewpoint, Darwin adds a vigorous defense of his argument. Darwin not only anticipates his opponents' chief objections but also shrewdly revises the definition of species and the principle of organic classification to fit a theory of descent with modification. Especially interesting in Darwin's defense is his discussion of the geological record. Here he first destroys the validity of the geological record as evidence, and then attempts to use that same record in support of his theory. The final chapter of this study evaluates the validity of Darwin's argumentative methods. Despite the overall strength of Darwin's argument and the attraction of natural selection as an idea, Darwin's argument for natural selection does not seem logically valid or scientifically accurate. The analogy that Darwin establishes between artificial and natural selection has serious flaws. Further, this analogy underestimates the power and effectiveness of artificial selection, a power evident in Darwin's own time. To make the operation of natural selection possible, Darwin postulates the existence of an imaginary and non-existent version of "nature", devoid of human control and resting on fragmentary geological evidence. Natural selection, a hypothetical principle of organic change in a hypothetical prehistory, assumes that man's presence hardly changes the power structure within organic nature. Faced, however, with the many examples of man's dominance over nature, the modern reader questions Darwin's argument for natural selection. On the contrary, man himself with his power of artificial selection seems to be the primary cause of organic change.