Although historians have carefully examined exactly what role the analogy between artificial and natural selection might have played in Charles Darwin's discovery of natural selection, philosophers have not devoted much attention to the way Darwin employed the analogy to justify his theory. I suggest that philosophers tend to belittle the role that analogies play in the justification of scientific theories because they don't understand the special nature of analogical inference. I present a novel account of analogical argument developed by Julian (...) Weitzenfeld and then use it to carry out an in-depth analysis of Darwin's argument from artificial selection. (shrink)

Various claims have been made, recently, that Darwin's argumentation in the Origin instantiates and so supports some general philosophical proposal about scientific theorizing, for example, the "semantic view". But these claims are grounded in various incorrect analyses of that argumentation. A summary is given here of an analysis defended at greater length in several papers by the present author. The historical and philosophical advantages of this analysis are explained briefly. Darwin's argument comprises three distinct evidential cases on behalf of natural (...) selection, cases, that is, for its existence, its adequacy and its responsibility. Theorizing, today, about evolution by natural selection involves a similar structure of evidential and explanatory concerns. (shrink)

In what follows, I consider the role of analogy in the first edition of Darwin’s Origin. I argue that Darwin follows Herschel’s methodology and hence exploits an analogy between artificial and natural selection that allows him generalize selection as a cause of evolutionary change. This argument strategy is not equivalent to an argument from analogy. Reading Darwin’s argument as conforming to Herschel’s two-step methodology of causal analysis followed by generalization allows us to understand the role and placement of Darwin’s discussion (...) of artificial selection in the Origin, without making the mistake of portraying Darwin’s argument for the existence and character of natural selection as an analogical argument. (shrink)

There are several interpretations of the argument structure of Darwin's Origin of Species, representing Covering-Law, Inference-to-the-Best-Explanation, and (more recently) Semantic models. I argue that while all three types of interpretation enjoy some textual support, none succeeds in capturing the overall strategy of the Origin, consistent with Darwin's claim that it is 'one long argument'. I provide detailed criticisms of all three current models, and then offer an alternative interpretation based on the view that there are three main argument strategies in (...) the Origin, all supporting the 'causal efficacy' of Darwin's theory. This interpretation provides both a more unified treatment of the text, and some important implications concerning the relation between general philosophical models of scientific theory support and specific historical cases. (shrink)

In what follows, I consider the role of analogy in the first edition of Darwin’s Origin. I argue that Darwin follows Herschel’s methodology and hence exploits an analogy between artificial and natural selection that allows him generalize selection as a cause of evolutionary change. This argument strategy is not equivalent to an argument from analogy. Reading Darwin’s argument as conforming to Herschel’s two-step methodology of causal analysis followed by generalization allows us to understand the role and placement of Darwin’s discussion (...) of artificial selection in the Origin, without making the mistake of portraying Darwin’s argument for the existence and character of natural selection as an analogical argument. (shrink)

The central role played by Darwin's analogy between selection under domestication and that under nature has been adequately appreciated, but I have indicated how important the domesticated organisms also were to other elements of Darwin's theory of evolution-his recognition of “the constant principle of change,” for instance, of the imperfection of adaptation, and of the extent of variation in nature. The further development of his theory and its presentation to the public likewise hinged on frequent reference to domesticates.We have seen (...) that Darwin's reliance on the analogy between domesticated varieties and wild species was a bold and original step, in light of contemporary views on the nature of domesticates. However, as Darwin undoubtedly foresaw, his reliance on the analogy created difficulties as well as solving problems, and these began with his Malthusian codiscoverer of the principle of natural selection, Alfred Russel Wallace. Wallace's paper “On the Tendency of Varieties to Depart Indefinitely from the Original Type,” presented to the Linnean Scoiety along with the first public unveiling of Darwin's theory, states: We see, then, that no inferences as to varieties in a state of nature can be deduced from the observation of those occurring among domestic animals. The two are so much opposed to each other in every circumstance of their existence, that what applies to the one is almost sure not to apply to the other. Domestic animals are abnormal, irregular, artificial; they are subject to varieties which never occur and never can occur in a state of nature.62Much has been made of the similarity of views of Darwin and Wallace, but this quotation surely reveals how utterly different their views were on what to Darwin was an important matter. Several critics of the Origin saw Darwin's reliance on the domesticates as his Achilles heel. As Young has pointed out, Samuel Wilberforce included the following passage in his attack on the Origin: Nor must we pass over unnoticed the transference of the argument from the domesticated to the untamed animals. Assuming that man as the selector can do much in a limited time, Mr. Darwin argues that Nature, a more powerful, a more continuous power, working over vastly extended ranges of time, can do more. But why should Nature, so uniform and persistent in all her operations, tend in this instance to change? Why should she become a selector of varieties?63Another critic, Fleeming Jenkin, found the analogy a weakness in Darwin's theory because of the limited extent of variation in any one direction in domestic animals and plants.64 We have already seen that Darwin had confided a similar view to his notebook thirty years earlier, but changed his mind as a result of his profound study of domesticates. De Beer's reference to “an English country gentleman's knowledge of domestic plants and animals and their breeding”65 fails totally to recognize the originality and depth of Darwin's knowledge of domesticates.Why did Darwin, against the currents of his time, rely so heavily on mankind's experience with domesticated organisms to shape his theory about species in nature? On reason is that only with domesticates was an approach that came close to experimental verification possible. Darwin fully realized the inadequacies of the experiment, as is emphasized by his repeated contrasting of selection under nature and selection by man. Yet the extensive experience and data of plant and animal breeders offered the only reliable base against which Darwin could continually challenge his views. As he wrote in the introduction to Variation, with domestication, “man ... may be said to have been trying an experiment on a gigantic scale.”66 Given Darwin's high opinion of the quantitative work of Malthus and Quetelet (as emphasized by Schweber),67 and his unremitting efforts to secure data by which to test his theories, it was inevitable that he should attach high significance to domesticated varieties. John Tyndall, in his Belfast address of 1874, said: “The strength of the doctrine of Evolution consists, not in experimental demonstration (for the subject is hardly accessible to this mode of proof), but in its general harmony with scientific thought.”68 Darwin would have agreed with the latter thought, but I think he would have challenged the preceding one on the grounds that long experience with domesticated varieties did provide an element of experimental demonstration. It gave him confidence in his theory, and he used his vast knowledge of artificial selection boldly and creatively. (shrink)

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One would think that after one hundred years of earnest work, Darwinians would know what it is that nature selects for. Yet while some Darwinians argue that nature selects only for genes, others insist that the units being selected for are organisms and groups of organisms. Darwinians have also had difficulty identifying the fundamental principles of their theory. Some think the basic principle is the survival of the fittest; others deny that this principle is an important part of their theory. (...) ;Philosophers of biology think that many of these fundamental issues could be resolved if we had a clearer understanding of evolutionary theory. Traditionally philosophers have tried to clarify scientific theories by formulating their central laws as universal statements in a formal language. This approach has been challenged recently by those who argue that theories should be thought of as sets of models, not as sets of universal statements. The central aim of my dissertation is to demonstrate how this shift in focus from statements to models can help resolve several long-standing problems associated with the theory of natural selection. ;In the first chapter, I identify the fundamental principles of Darwin's original theory of natural selection. I do so by ignoring Darwin's generalizations and focusing on the models of natural selection presented in the Origin as imaginary illustrations. I clarify Darwin's analogical argument for natural selection in the second chapter. My analysis is based upon the view that analogical reasoning involves using specific information about one model to infer specific information about isomorphic models. In the third chapter, I argue that the principle of the survival of the fittest is untestable and plays no role in specifying the models of natural selection. The fourth chapter concerns the units of selection controversy. I argue that many selection processes can be accounted for by more than one model and that the choice between them is often a pragmatic one. While the four chapters deal with different problems, they are related by their common perspective on the structure of scientific theories, a perspective which I suggest is largely responsible for their individual successes. (shrink)