Intelligent Design, the best explanation of Origins

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Darwin and Teleology

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1 Darwin and Teleology on Tue Sep 05, 2017 11:41 am

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Teleological explanations have played a central role throughout the history of the life sciences. Biological textbooks invariably suggest that teleological explanations were expunged from the physical sciences in the seventeenth century and finally, thanks to Charles Darwin, from the biological sciences in the nineteenth. And yet the same textbooks often explain adaptations by reference to natural selection in language that sounds suspiciously teleological. “That color pattern is present in the males of that population of fish because it increases their attractiveness to female mates without increasing their visibility to predators.” Moreover, explanations that at least appear to be teleological are not restricted to the observable, phenotypic adaptations of vertebrate behavior. Notice the explanatory structure implicit in the following quotation from 

Albert Lehninger’s Bioenergetics: The Molecular Basis of Biological Energy Transformations (1971, 110; emphasis added). 

Thus photo-induced cyclic electron flow has a real and important purpose, namely, to transform the light energy absorbed by chlorophyll molecules in the chloroplast into phosphate bond energy.

A common response to passages such as this is to say that the use of the term “purpose” is merely a kind of shorthand for a more complicated mechanical explanation, not evidence of a commitment to teleology. Yet this passage is embedded in a detailed description of the mechanisms of photosynthesis, and historically the discovery of the process described led to a quest for its purpose. Biochemists did not feel that they understood cyclic electron flow until they figured out its biological function.

There is a concern that such explanations imply some sort of conscious, or anyway cognitive, agency – either in the form of an external, perhaps divine, agent, or in the form of an inherent drive or vital power. Much philosophical effort has been devoted in the past fifty years or so to making sense of natural teleology as a distinctive mode of explanation without accepting either of those implications.

At the most abstract level, three distinct positions have been defended regarding the legitimacy of teleological explanation in natural science, and all have their roots in ancient Greece.
Plato’s Timaeus and Laws argue that much about the natural world can be accounted for only by supposing the operations of an intelligent and beneficent God (in fact one with a penchant for mathematics), a view I refer to as “unnatural teleology.” Unnatural teleology takes the application of teleological explanation to natural phenomena to depend on the natural world being an artifact of a divine, extranatural, intelligent agent.

Aristotle’s Physics and biological writings defend what I term “natural teleology,” according to which the natures of living things act for the sake of their own development and preservation. On this view, there may be a place for the use of analogies drawn from human crafts in thinking about teleology, but teleology is an entirely natural phenomenon.

Finally, the Greek atomists argue against the legitimacy of teleological explanation in nature, the anti-teleology position. The unnatural “intelligent design” model found in Plato was melded to Christianity in the medieval period, and various medieval commentators on Aristotle attempted to downplay the differences between Plato and Aristotle on this score in the interests of integrating Aristotelian philosophy and
Christian theology.

The story gets more complicated in the early modern period, primarily because of three distinct, nonatomistic voices arguing against the legitimacy or value of teleological reasoning in natural science. René Descartes injects a new,
skeptical argument against the use of teleology in natural science – it is presumptive to think we can discern God’s plans by studying his creation. Francis Bacon argued that final causes are of value only in the study of human affairs; in the study of nature, they are “barren virgins.” Baruch Spinoza argued against teleology on grounds of a thoroughgoing determinism – natural events did not happen for the sake of some end but were inevitable manifestations of God’s nature.

But teleology was not without powerful allies in the seventeenth century. Robert Boyle in Disquisition about the Final Causes of Natural Things and John Ray in his The Wisdom of God as Manifest in the Works of Creation develop a Christian version of Platonic unnatural teleology into the form that comes to be known as natural theology, the form of teleological reasoning that Darwin studied carefully in the writings of William Paley in his years at Cambridge . In his unpublished autobiography, Darwin reports that as an undergraduate he did not question Paley’s premises and was thoroughly convinced by his logic (Plate XXII). By contrast, in the eighteenth and early nineteenth centuries there were also defenders of teleology who aimed to distance their defense of final causes from an unnatural source, in particular in Germany (relying on Kant’s Critique of Teleological Judgment) and France (Georges Cuvier’s principle of “conditions of existence” is often associated with final causes in the literature of this period). Because the context for this entry is evolution, in the following section I focus on the interaction between Charles Darwin and those more or less explicitly influenced by natural theology.

Darwin described himself as engaged in a teleological enquiry, a search for the final cause of a particular feature of these two varieties of plants. And he refers to the different mechanisms to encourage intercrossing in different
plants as contrivances that are present for the sake of that end. Darwin (1862c) had earlier written a well-received study of the “contrivances” found in orchids to promote fertilization by insects. That work was much admired by Asa
Gray, a self-taught American botanist who in 1842 had been designated the Fisher Professor of Natural History at Harvard College. Darwin and Gray began corresponding on botanical topics in 1855, and in 1857 Darwin revealed to Gray, a reform Presbyterian, that he was working on a book that will present a new theory of species transformation – and was pleasantly surprised by Gray’s cautiously positive reaction. Emboldened, later that year Darwin sent Gray a brief sketch of his theory. This sketch was then incorporated into the material presented, along with Alfred Russel Wallace’s “On the Tendency of Varieties to Depart Indefinitely from the Original Type,” to the Linnean Society in 1858 – Darwin’s first public presentation of his theory of natural selection.

A year later he was to publish the work that was to introduce evolution by natural selection to the biological sciences, On the Origin of Species. The Origin characterizes natural selection as a goal-directed, teleological force. In introducing the concept in chapter 4, for example, he speaks of it “daily and hourly scrutinizing throughout the world, every variation, however slight; rejecting that which is bad, preserving and adding up all that is good” (1859, 84); and he goes on to tell us that “natural selection can act only through and for the good of each being.” And, in a later appreciation of Darwin, Gray (1874, 80) makes direct reference to the overtly teleological character of the botanical work published after the Origin, urging Darwin’s readers to “recognize Darwin’s great service to natural science in bringing back to it Teleology; so that, instead of Morphology vs. Teleology, we have Morphology wedded to Teleology.” We find similar language already in his 1862 review of Darwin’s monograph on orchid fertilization, in which Gray (1862b, 428–29) applauds Darwin for having “brought back teleological considerations into botany.” In response, Darwin (DCP, 9483, letter from Darwin to Gray, 5 June 1874) underscores his agreement with Gray’s characterization of his theory as teleological: “What you say about Teleology pleases
me especially and I do not think anyone else has ever noticed the point.” And though “Darwin’s Bulldog,” Thomas Henry Huxley (1893, 86), is ambivalent about Darwin’s obsession with adaptation, he makes much the same point as Gray: “The apparently diverging teaching of the Teleologist and of the Morphologist are reconciled by the Darwinian Hypothesis” (on Gray and Huxley, see Ruse 2003, ch. 7).


1. The Cambridge Encyclopedia of Darwin and Evolutionary Thought, page 153

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