Richard A. Richards
Darwin’s philosophical impact derives from his naturalism and explanatory pluralism. His naturalism is constituted by the requirement that causes be observed and to the degree observed; the requirement that causes unify phenomena by explanation; and a continuity thesis that humans are part of nature and are to be explained on the same principles as other organisms. His explanatory pluralism not only appeals to natural selection, but also to sexual selection, evolutionary ancestry and more. The philosophical impact of this naturalism can be seen in the pragmatic naturalization of inquiry, the development of a historical metaphysics, and the contemporary evolutionary accounts of human psychology and social ecology. These pose challenges to traditional philosophical ways of conceiving human psychology, moral judgment and normativity, based on among other things, the assumptions about the nature of value, the roles of reason and emotion, and the functioning of moral judgments.
The scientific significance of Darwin and his theory of evolution is obvious. Evolutionary theory has become the foundation of modern biology, and has been extended to a variety of other fields. We find, for instance, evolutionary explanations and models beyond the traditional biological disciplines into psychology and social psychology, anthropology, economics and linguistics. Recognition of this influence has lead many commentators to classify Darwin with Newton and Einstein in the pantheon of scientific greats.
The philosophical impact of Darwin and his theory of evolution, on the other hand, is less obvious and more controversial. Introductory philosophy textbooks typically include few if any readings on, or references to evolution. Consequently, an introductory course in philosophy might never even have a discussion of Darwin or his theory of evolution. This suggests that many philosophers might well agree with Ludwig Wittgenstein in his Tractatus: “The Darwinian theory has no more to do with philosophy than has any other hypothesis of natural science” (Wittgenstein 1960: 4.1122). For Wittgenstein, Darwinism was irrelevant to philosophy because philosophy was restricted to “the logical clarification of thoughts” (Wittgenstein 1960: 4.112 emphasis added). If so, we can understand why an empirical theory such as Darwin’s would seem irrelevant. But not everyone conceives philosophy in this narrow way, and Darwin’s views have been incorporated by a variety of philosophical thinkers from the American Pragmatists, to the many philosophers who write and work in a variety of the contemporary disciplines and subdisciplines of philosophy, from philosophy of biology, philosophy of mind, to evolutionary ethics and evolutionary epistemology. Among those who see the relevance of Darwinism, there are some who think its influence to be pervasive. Daniel Dennett, for instance, claims that “The Darwinian Revolution is both a scientific and philosophical revolution …” and “In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning, purpose with the realm of space and time, cause and effect, mechanisms and physical law” (Dennett 1995: 21). More centrist are the views of philosophers such as Philip Kitcher who see a role for Darwin, but a relatively modest one. In a recent essay he tells us: “Philosophers should find it worthwhile to read Hume and Darwin, Kant and Einstein, Descartes and Chomsky … I want to make a particular case for bringing Darwin on to the philosophical team, not as the star player who wins the day all by himself, but as a contributor to a much larger effort” (Hodge and Radick 2003: 400).
The central question for this essay is the extent and nature of Darwin’s impact on philosophy. But first, we should notice that there are really two questions here. First is an historical question: to what extent did Darwin and his theory of evolution actually affect the practice and content of philosophy? This question is to be answered by reference to threads of actual influence. There is also a second, more philosophical question: what is the philosophical impact of Darwin when we trace out its proper consequences – whether or not this impact has been fully recognized? This is more a question about what the impact of Darwinism should be if understood correctly. I shall not treat these two questions separately, although I hope it will be clear throughout this essay which sort of impact is in question.
As we shall see, there are three main sources of Darwin’s philosophical influence. First is his naturalistic treatment of humans and their activities. This has a substantive component: we should explain humans and their activities as we explain other parts of nature because humans are part of nature. There is also a methodological component: we should use the methods of science to understand humans because science is the best way to approach our understanding of a natural phenomena. And because Darwinism is grounded on a scientific approach, it is often not philosophers, but scientists who have come to be most engaged in teasing out the philosophical consequences of Darwinism. The second area of influence is in the use of evolutionary models to conceptualize and understand various phenomena. We can, for instance, treat scientific, conceptual or ethical change as instances of selection based processes, even though strictly speaking they are not biological processes. Third, Darwinism has impact in that it provides a way to think about philosophical issues historically and scientifically, providing an alternative to the traditional philosophy of the last century or so that focuses on linguistic practices, intentional explanation and self-conscious introspection.
It would be possible to approach the question of Darwin’s philosophical impact strictly through the traditional philosophic divisions – epistemology, metaphysics, ethics and aesthetics. Darwin’s naturalism, however, suggests a slightly different approach, one based on the questions he began with, his methodology, and how it led to the answers he gave. We can then trace the implications of his answers to various questions, and see how they influence more recent thinkers and cross traditional philosophical divisions. On this approach, we will be able to see, for instance, how a Darwinian account of reason and emotion has implications for epistemology, ethics, and aesthetics. The organization of this essay will on that basis be as follows: The second section is a brief sketch of Darwin’s life, his work, and his context. Following that is a section on Darwin’s philosophical naturalism. The fourth section, “The Pragmatic Naturalization of Inquiry,” addresses the influence of Darwin on Pragmatic conceptions of philosophical inquiry, truth and meaning. In the fifth section, we briefly look at the implications of Darwinian naturalism on more recent metaphysical speculation. The sixth section sketches out a Darwinian account of human nature in terms of human psychology and social ecology. Finally I consider some standard philosophical objections to Darwinism and conclude with a few thoughts about the scientific challenge posed by Darwinism to traditional philosophy.
Darwin was born in 1809, the fifth of six children, to a wealthy and well-educated British family. His father, Robert Darwin, was a successful physician. His grandfather, Erasmus Darwin, was a poet and evolutionist. His mother, who died when Charles was eight years old, was the daughter of Josiah Wedgewood, founder of the Wedgewood ceramics dynasty. While both sides of Darwin’s family were largely Unitarian, his father was free thinker, and his mother’s side had Anglican sympathies. Darwin himself was baptized into the Anglican Church.
Darwin’s early education was as an unenthusiastic boarder at the Shrewsbury School. In 1825, he attended the University of Edinburgh, with the intention of studying medicine. But his interest in medicine studies was diminished by the brutality of unanaesthetized surgery. While in Edinburgh, he joined the Plinian Society, a group of students interested in natural history, sat in on a course in geology, and received training in systematics. In 1827, Darwin left the scientifically oriented University of Edinburgh for Cambridge University. At the time, there was little formal scientific education at Cambridge. One could not major in a science, although there was a smattering of optional lectures on scientific topics. Those with scholarly ambitions could enroll in honors, but studies there were limited to math and the classics. In the 1820s Oxford and Cambridge were just beginning to appoint chairs in the sciences, but often those appointed would have little scientific experience. Adam Sedgewick, for instance, was elected chair of geology without a background in geology, on the promise that he would learn some (Ruse 1999: 22).
Even though the formal science training at Cambridge left a lot to be desired, there were other opportunities. Darwin learned about beetle collecting from his cousin, W. Darwin Fox, who introduced him to the Reverend John Stevens Henslow, professor of Botany. Darwin became good friends with Henslow, attended his lectures on botany, and enjoyed evening discussions with him and others on a variety of scientific topics. Through Henslow, Darwin also became acquainted with some of the most important scientific thinkers of his time: Sedgewick, who, true to his promise, learned geology; the mineralogist and historian of science William Whewell; and the astronomer John Herschel. By the time Charles Darwin left Cambridge in 1831, his informal studies and connections with the scientific community put him well on his way to a career in the sciences.
During this time at Cambridge, Darwin’s enthusiasm for a scientific career was reinforced by his reading of Herschel’s newly published Preliminary Discourse on the Study of Natural Philosophy – a systematic theory of scientific method; and Alexander von Humboldt’s Personal Narrative of Travels to the Equinoctial Regions of the New Continent – a romanticized account of a scientific expedition to Tenerife and South America. Inspired by Humboldt’s travel narrative, Darwin planned a trip to Tenerife that was sadly waylaid by the death of his intended travel companion. Shortly thereafter, Darwin was chosen to accompany a young Captain Fitzroy on a journey aboard a ship named “The Beagle” to South America, that left England on 11 Dec. 1831. On this voyage Darwin brought along and read the first volume of Charles Lyell’s Principles of Geology, and received the anxiously awaited second volume in Montevideo in 1832. Through his continuing correspondence with Henslow, Darwin was also maintaining and expanding his scientific network back in England, impressing both Sedgewick and Lyell, who wanted to meet him on his return. On the Beagle voyage Darwin visited with John Herschel, who was mapping the heavens at the Cape of Good Hope. When Darwin returned to England in 1836, it was to a supportive and respectful network of scientists.
In the year following his return, Darwin began thinking seriously about Herschel’s “mystery of mysteries” – the origin of species. In 1837, he began his transmutation notebooks to organize his thoughts on the topic. While Darwin was already well on his way to accepting the transmutation of species, he believed that he lacked an adequate mechanism of change. In 1838, he read an essay by Thomas Malthus, and concluded that he finally had a mechanism. In this essay, Malthus highlighted the differential between normal reproduction rates and the resources required for survival. As Malthus put it: population increases geometrically, while food supply can only increase arithmetically. But while Malthus seemed to be arguing for the necessity of reproductive limits, Darwin concluded something very different.
In October 1838, that is, fifteen months after I had begun my systematic enquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved and unfavourable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work. (A: 120)
This was a watershed moment. Darwin had been looking for a mechanism of change, and Malthus gave it to him – natural selection. For the next four years Darwin worked on his transmutation hypothesis, and put together his ideas in a “sketch” in 1842. He elaborated on these ideas in a longer essay in 1844. But while Darwin engaged in correspondence with his friends about many of his ideas, he published nothing advocating his transmutationist ideas.
In 1846 Darwin set aside his evolutionary theorizing for a detailed study of barnacles. This study lasted eight long years, and resulted in an extremely detailed and careful manuscript that earned Darwin a Royal Society medal. Darwin’s barnacle study did two things. First it established him as a legitimate authority among scientists. This would later help him in the initial reception of his Origin of the Species. Second, it gave him a much clearer idea of the extensive variability in nature. Before his study on barnacles, he thought variability within a species to be the exception rather than the rule. In 1854 Darwin returned to his theorizing and began gathering his notes and thoughts for a manuscript he described as “The Big Species Book.” But in 1858, while this book was still less than half finished, he received a letter and essay from the naturalist Alfred Russell Wallace, arguing for a theory of transmutation almost identical to his own. A crisis in priority for Darwin was averted when Charles Lyell and Joseph Hooker arranged to have Wallace’s essay read before the Linnaean Society along with an abstract of Darwin’s manuscript. At the time this meeting attracted relatively little attention, but it prompted Darwin to devote himself full time to the production of a longer abstract of his big species book (Browne 2002: 33–42). In November of 1859 this abstract was published under the title: “On the Origin of Species by Means of Natural Selection.”
In the Origin, Darwin argued for three main hypotheses. First was the transmutation hypothesis: new species originate from the modification of other species. Second was common ancestry: speciation occurs through a branching process in a tree like structure. All species therefore share a common ancestor at some point in the evolutionary past. Third, was a causal mechanism: natural selection was the main, but not exclusive mechanism for change. Here Darwin argued: (1) there is variation among all organisms; (2) because more organisms are born than can survive and reproduce there will therefore be a struggle for existence; (3) some individual organisms will be better adapted to survive and reproduce; (4) these individuals will pass on their traits to offspring; (5) this will result in a gradual modification of the species. At the end of the Origin, Darwin turned to the explanatory power of these three hypotheses – transmutation, common ancestry, and selection as mechanism – arguing that they could explain a variety of phenomena from geographical distribution, embryological development, rudimentary organs, to the patterns of morphological similarity among species.
The response to the Origin was all the publisher could have desired. The first printing sold out in one day and a second printing was issued a month later. There were numerous reviews, many positive, and even those that were not were often sympathetic, based on Darwin’s reputation and previous work (Browne 2002: 101). Those in Darwin’s network were particularly impressed. Lyell, for instance, called it “A splendid case of close reasoning & long sustained argument …” even though he could not agree with all of its conclusions (Browne 2002: 90). When there was criticism, it was typically not based on conflict with the account of origins in Genesis. Familiarity with German “literary” Biblical criticism precluded this sort of literalism among most educated British (Ruse 1999: 239). Criticism instead often focused Darwin’s methodology. One standard objection was that Darwin was not being inductive enough, and was dabbling in hypotheses (Hull 2003). The rhetorical value of this was well entrenched. After all, it was long known that the great Isaac Newton himself “feigned no hypothesis” and the proper method was “Baconian” – based on the prescriptions of Francis Bacon. There was also a second question about the adequacy of natural selection to produce the obviously adapted forms we observe in nature. Lurking here was the assumption that a divine “designer” was required. This question was raised both by Darwin’s critics and his most loyal supporters.
In the Origin, Darwin had little to say about human evolution, knowing full well the controversy it would create. Only at the very end does he explicitly address the topic:
In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history. (O: 488)
Darwin does not elaborate further in the Origin. His conscious avoidance of this topic, however, did not prevent both his critics and supporters from addressing it. There seemed to be three main issues. First was the question of common ancestry. In the Origin, Darwin seemed to be implying that humans descended from apes and monkeys. (It was perhaps too subtle to insist that he instead implied humans shared a common ancestor with modern apes and monkeys.) This was the focus of a famous debate in 1860 between T. H. Huxley – “Darwin’s Bulldog” and Bishop Wilberforce (Browne 2002: 122). The second issue was the matter of the differences between humans and other primate species. Richard Owen claimed that humans were different in kind from other species, by virtue of a unique structure in the human brain – the hippocampus minor. This particular claim was quickly rejected by 1861, based on Huxley’s article in the Natural History Review demonstrating that the hippocampus minor is also found in nonhuman primates (Browne 2002: 119).
The third issue was whether the existence and nature of humans could be explained in the same way other species were explained. Lyell, in his 1863 Antiquity of Man, gave natural selection a role, but seemed to reserve a place for a “guided saltatory mechanism” (Ruse 1999: 145). He could just not give up the idea that man’s creation was guided by, and explained by a greater power – even if this creation was still subject to the laws of nature. Wallace was similarly inclined. He worried that the higher mental faculties of humans could not be explained through natural selection alone. Even “savages,” according to Wallace, possessed mental faculties in excess of what was needed for survival. He concluded: “a superior intelligence has guided the development of man in a definite direction, and for a special purpose, just as man guides the development of many animal and vegetable forms” (Ruse 1999: 246). But Darwin had little sympathy for those who, like Lyell and Wallace, wanted to bring God back into the explanation. In 1871 he published his Descent of Man and Selection in Relation to Sex, which addressed human evolution naturalistically and in much more detail.
In the introduction to the Descent of Man Darwin explained his reticence in discussing humans in the Origin, and indicated that given the widespread acceptance of evolution, there was no longer a need to put off discussion of man. His goals, he claimed, were first to establish that man has descended from some pre-existing form; second, to explain the manner of his development; third to consider the differences in the “so-called races of man” (DM: 3). The evidence he gave in chapter 1 for human descent will be familiar to anyone who has read the Origin: homologous structures in man and lower animals, development, and rudimentary structures. More important for purposes here however, is Darwin’s discussion of mental powers in chapter 2. Here he argued that the differences between humans and the higher apes are only of degree, and relative to all aspects – instincts, curiosity, imitation, attention, memory, imagination, reason, tool and weapon use, language, self-consciousness, sense of beauty, belief in God, spiritual agencies and superstitions.
In chapter 2, Darwin also addressed the origin and development of languages, proposing his own evolutionary explanation.
We see variability in every tongue, and new words are continually cropping up; but words, like whole languages, gradually become extinct … As Max Muller has well remarked: – ”A struggle for life is constantly going on amongst the words and grammatical forms in each language. The better, the shorter, the easier forms are constantly gaining the upper hand, and they owe their success to their own inherent virtue.” (DM: 60)
Darwin concluded: “The survival or preservation of certain favoured words in the struggle for existence is natural selection” (DM: 60–1). What is important in this passage is that instead of just explaining the appearance of language through the biological evolution of humans, Darwin was applying an evolutionary model to linguistic processes. He was using the conceptual framework he applied to biological evolution to the non-biological change and development of languages.
At the beginning of the Descent then, we have Darwin laying out two different strategies for using evolution to understand human phenomena. The first is to treat humans and all their physical, mental and social traits as products of biological evolution. This is a thoroughgoing naturalism. The second is to use a model of change, derived from biological evolution but not itself biological, to explain historical origins and processes of change. In the remainder of the Descent, Darwin employed these strategies to explain human psychological faculties such as reason, emotion and the social instincts. Here Darwin also employed a continuity assumption that human faculties and social nature are to be explained in terms of the same causes we explain the faculties of other species. Finally, he adopted an explanatory pluralism. While natural selection explained some human features, other features were explained by sexual selection, ancestry, effects of the environment, use and disuse, and learning.
The Descent sold well and Darwin made a substantial profit. In 1872, the year after the publication of Descent, Darwin wrote and published his Expression of the Emotions in Man and Animals. He laid out his general principles of expression in the first three chapters, with illustrations from man and other species, cats and dogs in particular. The means of expression occupy the next several chapters. Specific emotions are addressed in the remainder – anger, sadness, grief, love and so on. The Expression initially sold well, but after a second edition appeared in 1889, seven years after Darwin’s death, it more or less disappeared from the intellectual landscape for nearly a hundred years. What is important here is that first, in both the Descent and Expression, Darwin was pursuing his project of understanding all things human naturalistically – including the “higher” human faculties such as reason, imagination, and the moral sense. Second, Darwin saw human nature as continuous with nonhuman nature. Humans may differ from other species, but they are also similar, in part because of shared ancestry.
The first sources for Darwin’s naturalism likely came from the books noted above, that he read in the year or so before his Beagle voyage. The Personal Narrative, a record of Humboldt’s expedition to South America, so enchanted Darwin that he would copy and read aloud passages to his fellow students, as he planned his own voyage (Richards 2003: 93). Part of the influence here on Darwin was surely its imaginative and romanticized description of travel to unexplored lands. But Humboldt’s voyage was not mere tourist travel, but an investigation into the “unity of nature.” At the onset of this voyage, he wrote:
In a few hours we sail around Cape Finisterre. I shall collect plants and fossils and make astronomic observations. But that’s not the main purpose of my expedition – I shall try to find out how the forces of nature interact upon one another and how the geographic environment influences plant and animal life. In other words, I must find out about the unity of nature. (Humboldt 1995: ix)
In the introduction to his Personal Narrative, Humboldt tells us that this unity of nature is to be reflected in the interconnections of science. In particular, he was interested in connecting the laws of life with those governing inanimate nature (Humboldt 1995: 6–7). Throughout his Personal Narrative, Humboldt makes it clear that he includes humans in this “unity of nature.” It was with this book and its picture of a grand interconnected nature, that Darwin later undertook his voyage on the Beagle. He described its significance in a diary entry written during his voyage back to England: “As the force of impression frequently depends on preconceived ideas, I may add that all mine were taken from the vivid descriptions in the Personal Narrative which far exceed in merit anything I have ever read on the subject” (Richards 1987: 93).
At about the same time Darwin was reading Humbold’s Personal Narrative, he was also reading Herschel’s Preliminary Discourse on the Study of Natural Philosophy, just published in 1830. John Herschel, son of the astronomer William Herschel, was the most prominent scientist in England. His Preliminary Discourse was widely read, with twelve published editions, and translations into French, German, Italian, Russian, Chinese and Arabic (Herschel 1996: xi). What was distinctive about this book was not just its systematic approach to scientific method, but also its account of scientific induction.
At the time, the term “induction” was associated with the views of Francis Bacon and Isaac Newton. But it was a slippery term, often meaning different things to different people at different times. Like many of his day, Herschel claimed to be advocating an inductive method along the lines used by the great Isaac Newton in the derivation of the universal law of gravitation. Induction, for Herschel, seemed to involve two main processes: first, the rise by inductive generalization from the observation of particular facts to empirical law, followed by the subsequent inference of higher level theoretical laws; second, the establishment of verae causae – true causes – by direct observation and analogy. The first process, begins with observation and generalizes to empirical laws, then derives higher level, more theoretical laws. The second process is, in effect, a rule governing causal inference. Science, according to Herschel is at its best when it explains phenomena in terms of already established causes. Herschel explains, then credits Newton:
Experience having shown us the manner in which one phenomenon depends on another in a great variety of cases, we find ourselves provided, as science extends, with a continually increasing stock of such antecedent phenomena, or causes … To such causes Newton has applied the term vera causae; that is, causes recognized as having a real existence in nature, and not being mere
hypotheses or figments of the mind. (Herschel 1996: 144) What is important here is how these vera causa are established. Herschel identifies two ways – direct observation and analogy. We can observe directly, for instance, the force exerted by whirling around a stone in a sling, and we can apply that by analogy to the orbit of heavenly bodies.
If the analogy of two phenomena be very close and striking, while at the same time, the cause of one is very obvious, it becomes scarcely possible to refuse to admit the action of an analogous cause in the other, though not so obvious in itself. For instance, when we see a stone whirled round in a sling, describing a circular orbit around the hand, keeping the string stretched, and flying away the moment it breaks, we never hesitate to regard it as retained in its orbit by the tension of the string, that is, by a force directed to the centre; for we feel that we do really exert such a force. We have then a direct perception of the cause. When, therefore, we see a great body like the moon circulating around the earth and not flying off, we cannot help believing it to be prevented from so doing, not indeed by material tie, but by that which operates in the other case through the intermedium of the string-a force directed constantly to the centre. (Herschel 1996: 149)
The details of Herschel’s views here are beyond the scope of this essay, but the main significance of his vera causa requirement is that we can postulate new causal hypotheses only if there is a sufficiently close analogy with already observed causes.
Charles Lyell, in the two volumes of his Principles of Geology (read by Darwin in 1831 and 1832), seemed to endorse the Herschellian methodology of science. This is clear in his rejection of “catastrophism,” that asserts geological features are to be explained in terms of a variety of catastrophic processes of biblical proportions – volcanoes, floods, earthquakes, rapid climate change. Lyell’s rejection of catastrophism was based on first, his actualism – we are to explain geological phenomena only in terms of the kinds of causes and processes that we observe around us; second, his uniformitarianism: we are to explain only in terms of causes to the degree that we observe them. We can explain in terms of floods and volcanoes, but only on the scale we observe. Lyell was clearly in agreement with Herschel about methodology – as both recognized in print (Ruse 1999: 59–61).
The fourth influence on Darwin was William Whewell, who was quoted by Darwin before the title page of his Origin. Whewell disagreed with Herschel about the vera causa requirement, arguing that it implied we could not discover new causes. For Whewell, induction consisted in the superimposition of a concept or idea on the phenomena via the “colligation” of empirical facts. Gravity, for instance, was a concept that colligated facts about the motion of heavenly bodies. But what was important for Whewell was explanatory power through consilience. A consilient hypothesis was one that not only explained the phenomena it was invented to explain, but predicted and explained additional phenomena. Not only could gravity explain the motion of the planets, but it could also explain the orbit of the moon around the earth, the ocean tides, and the descent of stones on earth (Whewell 1989: 328–30). In effect, the consilience requirement is a rule of explanatory unification.
It is beyond the scope of this essay to work out in detail the actual historical influence of Humboldt, Herschel, Lyell and Whewell on Darwin. Nonetheless, we can easily find the broad themes outlined above throughout Darwin’s work. Humboldt’s holism and treatment of humans as part of the interconnected unity of nature are seen in the broadest and most important features of Darwin’s work – in his application of the same laws to all of life from barnacle to humans. Similarly, Herschel’s views are echoed in Darwin’s attempt to establish that natural selection is a vera causa by direct observation in domestic breeding. Because breeders do not select for the benefit of the individual organisms, they typically reduce the fitness of the organisms being bred. It is possible to observe the elimination of the less fit in natural selection, as Darwin thought had happened with the highly modified Niata cattle in South America (Richards 1997). Lyell’s methodological prescriptions can similarly be seen in Darwin’s work. At the same time Darwin was establishing that natural selection was a Herschellian vera causa, he was also conforming with his gradualism to Lyell’s requirements that postulated causes must be among those known to operate and to the degree observed. Finally, Whewell’s consilience requirement was satisfied in the penultimate chapter of the Origin, where Darwin argues first that his theory can explain various and different “classes of facts” from classification and comparative morphology, to rudimentary organs, embryology and geographic distribution; and second, that this explanatory ability is sufficient reason to accept it as true (O: 457–8).
One implication of Darwin’s naturalism is that it seems to rule out a variety of the “exemptionalist” theories that treat human nature as unique and requiring unique kinds of explanations. Theistic exemptionalism, for instance, might explain human nature by reference to a God that created man in his own image. Darwin’s rejection of this sort of explanation not only put him at odds with opponents of his evolutionary theory, but many of his supporters, including A. R. Wallace, the co-discoverer of natural selection, as well as Charles Lyell and Asa Gray (Richards 1987: 178–85). Darwin’s rejection of these theological tendencies would be expected given his methodological commitments. Unless God could be observed, or shown to be a close analogy to an observed cause, then he could not be established as a Herschellian, empirical vera causa.
Other exemptionalist approaches seem to be ruled out by Darwin’s naturalism as well. Approaches that conceive humans as different in kind from other animals, based on the uniqueness of human reason, language or culture violate Darwin’s continuity principle. Human divergence from animals in terms of reason is a matter of degree, to be explained as a variation on the same faculty possessed by animals. While humans may differ from the great apes in terms of the degrees of reason, ability to communicate or form culture, there are also obvious similarities. And, as Darwin noted, the differences are even greater between the great apes and fish. So if we are to say humans and apes are different in kind, should we not also say that of apes and fishes?
If no organic being except man had possessed any mental power, or if his powers had been of a wholly different nature from those of the lower animals, then we should never have been able to convince ourselves that our high faculties had been gradually developed. But it can be clearly shewn that there is no fundamental difference of this kind. We must admit that there is a much wider interval in mental power between one of the lowest fishes, as a lamprey or lancet, and one of the higher apes, than between an ape and man; yet this immense interval is filled by numberless gradations. (DM: 34–5)
It is also important to notice that Darwin did not focus exclusively on natural selection as the causal force for change. He employed explanations based on a variety of factors including the “conditions of existence,” “use and disuse” and “correlation of parts.” Perhaps most importantly, he recognized a second form of selection – sexual selection. The title of his book on human evolution is, after all, The Descent of Man, and Selection in Relation to Sex. Here Darwin first introduced sexual selection in humans as a possible explanation for the differences among the human races (DM: 250). He then laid out the general principles governing sexual selection, giving examples from molluscs, crustaceans, butterflies, moths, birds, reptiles, and dogs. The idea behind sexual selection is simple. First, just as there is a struggle to survive, in sexual species there is also a struggle to reproduce, primarily but not exclusively, a struggle among males for females. This struggle takes two forms – a physical struggle with other male rivals, and a struggle for the attention of the female (DM: 398). Second, those individuals that do best in this struggle are more likely to reproduce, passing their traits on disproportionately to the next generation. Sometime the traits that are useful in the struggle to reproduce are not useful in survival. The peacock’s tail, for instance, is useful in attracting the attention and charming peahens, but it is also a hinderance in survival, reducing the ability of peacocks to avoid predators. Sexual selection can potentially explain traits not explainable by natural selection. This suggested to Darwin that sexual selection might be able to explain the excess human cognitive abilities that Wallace, Lyell and Gray thought inexplicable by natural selection (DM: 402).
What we have here in Darwin’s naturalism, then, is first an approach based on an assumption about the continuity of nature from invertebrates to birds, apes and humans; second, a methodological, empirical vera causa rule that allows only observationally grounded hypotheses; and third, an explanatory unification vera causa requirement. And finally, we have an approach that is pluralistic, employing explanations based on natural selection, sexual selection, common ancestry and more.
In the years following the publication of the Origin, Darwinian evolution was much discussed in broader philosophical contexts. Nowhere was this more apparent than in “pragmatism,” the most openly Darwinian of philosophical movements. The pragmatists did not typically embrace Darwin’s naturalism in its entirety, but they applied its insights to important philosophical topics. Darwin’s influence on the pragmatists came through Chauncey Wright, a mathematician and student of Asa Gray. Wright adopted Darwin’s views shortly after reading the Origin in 1860. He corresponded with Darwin, defended Darwin in print, and earned the respect of Darwin (Wiener 1949: 31). Wright was also part of a group of young philosophers who began meeting regularly in Cambridge, Massachusetts in the early 1870s. This group, called the “metaphysical club” by Peirce, consisted of Wright, Charles Peirce, William James, Oliver Wendell Holmes, Frank Abbott and Nicholas St John Green. According to Peirce, Wright was the central figure in this club, and its most powerful and assertive intellect:
Chauncey Wright, something of a philosophical celebrity in those days, was never absent from our meetings. I was about to call him our corypheus; but he will better be described as our boxing master whom we – I particularly – used to face to be severely pummeled. (Wiener 1949: 19)
Wright’s significance here was, of course, less his pugilistic skills, than the fact that he was a tireless advocate of Darwin’s theory of evolution.
Charles Peirce was clearly influenced by Wright’s Darwinism, but he also went far beyond a Darwinian naturalism into sometimes obscure metaphysical musings (Wiener 1949: 70–96). Nonetheless, Peirce’s views about philosophical inquiry are Darwinian. According to Peirce, “logicality” is an adaptation produced by natural selection, useful in survival.
We are, doubtless, in the main logical animals, but we are not perfectly so … Logicality in regard to practical matters is the most useful quality an animal can possess, and might, therefore, result from natural selection. (Menand 1997: 10)
Inquiry is something that “logical” organisms (such as humans) do in response to problems posed by their environment that generate doubt. Since this doubt is uncomfortable, producing a kind of irritation, the organism tries to eliminate the doubt. It does this through an inquiry, the proposal of an hypothesis to dispel the doubt. If the hypothesis succeeds, it results in belief – the satisfaction of doubt, that then guides our actions (Menand 1997: 13–14, 33). A satisfactory belief will bring us into a state of adaptation to our environment, until some problem forces us again into a state of doubt, and we begin a new inquiry.
Like Peirce, William James applied Darwinian ideas to inquiry. According to James, beliefs are tools or instruments of action to guide our living in the world (Menand 1997: 114). True beliefs are those that work, false beliefs are those that don’t. Where James disagreed with Peirce is his view that the success of beliefs depends not just on the world, but also on individual tendencies, preferences, and pre-existing belief. A particular belief might work well for me, but not for you (Menand 1997: 101). This is because each person has a different set of background beliefs, tendencies and preferences, and for a belief to work, it must work relative to both an environment and the organism, as James explains:
A new opinion counts as “true” just in proportion as it gratifies the individual’s desire to assimilate the novel in his experience to his beliefs in stock. It must both lean on old truth and grasp new fact … . (Menand 1997: 102–3)
The functioning of beliefs not only varies among individuals, but may change over time. As an environment or an individual changes, the utility of a belief may change.
Oliver Wendell Holmes applied Darwinian ideas to the law, arguing that we should conceive of laws as tools, and interpret and evaluate them based on how well they work. What are the consequences of conceiving a law in a particular way? Is a law, interpreted in a particular way, adaptive in the sense that it works well in social circumstances (Menand 1997: 156–7)? We can think of this in more general evolutionary terms. Humans, like other social species, adopt rules of social interaction. For humans, these rules are not purely instinct, but learned through interaction in the social environment. And for humans they get expressed in language and institutionalized in legal systems.
Darwinian ideas were also applied pragmatically by John Dewey in his conception of experience. Instead of thinking of experience as the passive reception of sensory experience, we should think of it as an interaction with a world of danger and risk. We act on the world, get a response, then act again. In effect, we experiment with our environment, and good experiments are those that are apt – help us adapt. Knowledge, for Dewey is a “mode of participation” in experience.
… The living creature is a part of the world, sharing its vicissitudes and fortunes, and making itself secure in its precarious dependence only as it intellectually identifies itself with the things about it, and forecasting the future consequences of what is going on, shapes its activities accordingly. If the living, experiencing being is an intimate participant in the activities of the world to which it belongs, then knowledge is a mode of participation, valuable to the degree to which it is effective. (Menand 1997: 210)
Like Peirce, James and Holmes, Dewey asked us to think about philosophical activities in Darwinian terms – as instruments for functioning in environments. In the time since Dewey pragmatism has become less explicitly Darwinian. Nonetheless, similar Darwinian ideas have been adopted and developed by contemporary philosophical thinkers.
If we think of metaphysics as that which lies beyond experience – and define it in these terms – then Darwin had little to say relevant to metaphysics. His naturalism precludes it. But if we instead think of metaphysics as the study of the fundamental kinds of things that exist and processes that operate, then there is much he could say. First, Darwinism seems to rule out the traditional essentialist view that species are “natural kinds.” Second, Darwin’s selection-based causal mechanisms provide a probabilistic and non-teleological explanation of order that requires no appeal to intentions – human or theistic. Third is an implicit conception of value that is naturalistic and relational, and based on contextual facts about functioning.
The usual story told by philosophers is that before Darwin, species were conceived as natural kinds with essences. These essences have often been identified with a set of necessary and sufficient properties. Elliott Sober explains this approach:
Essentialism is a standard philosophical view about natural kinds. It holds that each natural kind can be defined in terms of properties that are possessed by all and only members of that kind … . (Sober 2000, 148)
As the story goes, this “property essentialism” is the view of Aristotle and Linnaeus (Dennett 1995: 36–7). Unfortunately this story is not accurate. Aristotle was more interested in classifying functional features of organisms to get at the important functional principles, than in classifying organisms into species on the basis of essential traits. And Linnaeus was a species essentialist only in the first editions of his Systemae Natura. In later editions he was a “genus” essentialist and then an “order” essentialist, where species were hybridizations from the God-created genera or orders. Furthermore, Linnaeus did not identify a particular set of properties with an essence. Essences were instead something underlying the changing form that was passed on in reproduction. Species had essences not because of their distinctive properties, but because of a genealogical connection to some original form created by God (Richards 2007).
Both versions of species essentialism seem incompatible with Darwinism. First, Darwin’s naturalism ruled out appeals to causes that could not be observed or connected to observation by analogy. Genealogical essentialism is ruled out if the essences passed on in reproduction cannot be observed. Second, Darwin’s gradualism implies that change is continuous and there is therefore no single set of unchanging properties to be associated with a species over time. Moreover, Darwin’s “population thinking,” that conceives of species as variable populations implies that at a single time there is no set of invariable properties associated with a species. All this caused Darwin to worry in the Origin that maybe there were really no such things as species (O: 52).
In the last fifty years, there has been a heated debate over how to best conceive species. The biological species concept many of us learn in introductory biology courses, asserts that species are groups of interbreeding or potentially interbreeding organisms. This concept is clearly inadequate, however, applying only to sexually reproducing species. In recent years, the number of species concepts in use has expanded to well over twenty. But while there is no consensus about which species concept is best, there is consensus that whichever concept we adopt, species are ultimately historical population lineages – groups of organisms connected by reproduction and ancestry that change over time (Richards 2007).
On the basis of this idea, David Hull has argued that species are like individual organisms – with origins and endings, cohesion and change over time – and should therefore be conceived as “historical individuals” (Ereshefsky 1992: 293–316). The advantage of this is that it focuses attention on the nature of change and the processes that govern the origin and endings of species lineages. Criticism of this proposal has centered on whether groups of organisms ever have sufficient cohesion to count as individuals and what would be required. Ruse, for instance, argues that species lack sufficient cohesion (Ereshefsky 1992: 343–62). Undeterred, Hull has extended this idea of individuality beyond its strict biological domain, arguing that we can conceive disciplines, conceptual systems and theories as individuals as well, since each sort of thing has a beginning and ending, cohesion and change over time (Ereshefsky 1992: 310–13). What is important with historical individuals is that they cannot be defined and don’t have essences. This has obvious implications for debates about human nature. If Homo sapiens is like any other species, and is conceived as a historical individual, then it has no essences and cannot be defined. And since the members of the human lineage have changed over time, and exhibit variability at any single time, then the best we can do is identify the distributions of particular changing traits at a given time and geographic location.
The second area of Darwinism’s metaphysical significance is its commitment to fundamental processes and explanations of order. Before Darwin, a standard explanation of order, exemplified by William Paley, was by divine intention. Nature has order because God gave it order. If we wanted to explain the vertebrate eye, for instance, we would have appealed to the design intentions of God. Darwin knew Paley’s argument well, but argued that order – apparent design – could instead arise spontaneously from the undirected processes of natural and sexual selection. This idea has two important implications. First, it suggests a general explanation of order that is non-directed, and spontaneous. Second, it seems to undercut Paley’s argument from design to the existence of God. If selection processes can explain apparent design in nature, we need not appeal to a designing God.
This second implication of Darwinian naturalism has been the source of much debate. Theists fear – while atheists celebrate – its apparent atheistic implications. As John Dupre puts it: “Darwinism undermines the only remotely plausible reasons for believing in the existence of a God” (Dupre 2005: 56). In Dupre’s view, Darwinism does not just imply an agnosticism – a suspension of belief, but an atheism – a denial of the existence of God. This view, however, is at odds with Darwin’s attitude and naturalism. While Darwin was never particularly religious, neither was he atheistic, even though his belief gradually weakened. By the time he wrote his Autobiography, he was resigned to an agnosticism: “The mystery of the beginning of all things is insoluble by us; and I for one must be content to remain an agnostic” (A: 94). This is just the attitude we should expect, given that his methodological naturalism not only prohibited the appeal to a God or a God’s intentions for any sort of explanation, but also seemed to rule out claims that go beyond observation to deny the existence of God.
Whatever its implications for theism, natural selection is now seen by many, not just as a fundamental biological process, but as an instance of a more general causal process. Daniel Dennett, for instance, has argued that natural selection is a universal, algorithmic and substrate neutral process for generating order. Selection, according to Dennett does not just work in the biological realm, but throughout nature, “promising to unite and explain just about everything in one magnificent vision” (Dennett 1995: 82). Richard Dawkins extends this idea of universal selection to culture by highlighting the similarities between genes and memes – ideas, habits, skills, behaviors, inventions songs and stories. Susan Blackmore explains:
Genes are instructions for making proteins, stored in cells of the body and passed on in reproduction. Their competition drives the evolution of the biological world. Memes are instructions for carrying out behavior, stored in brains (or other objects) and passed on by imitation. Their competition drives the evolution of the mind. Both genes and memes are replicators and must obey the general principles of evolutionary theory and in that sense are the same. (Blackmore 1999: 17)
If Dennett, Dawkins and Blackmore are right, then the same fundamental processes that govern biological evolution to produce biological order, govern conceptual and cultural evolution to produce order there as well.
This idea of extending selection beyond biology is made possible partly through the general theory of selection formulated by David Hull. According to Hull, selection really consists of two component processes – replication and interaction. Adopting this model, he argues is a better way to understand both biological and non-biological selection processes. Hull proposes that we replace the hierarchy of genes, organisms and species, with the more general replicators, interactors, and lineages, that can apply anywhere there is selection (Hull 2001: 2).
Replicators are things that produce copies of themselves. Genes are the paradigm case, but some organisms can replicate themselves as well. Interactors are “those entities that interact as cohesive wholes with their environments in such a way as to make replication differential” (Hull 2001: 22). Organisms are paradigm interactors, but genes and chromosomes can interact in their environments as well. Higher levels can also serve as interactors, in the instances where colonies, hives, and other kinship groups function as cohesive wholes. Lineages can be constituted by either interactors or replicators. Selection then, “can be characterized generally as any process in which differential extinction and proliferation of interactors causes the differential perpetuation of the replicators that produced them” (Hull 2001: 22).
Critics have responded to Hull’s analysis by arguing that such a general theory is not possible because genes, organisms, cultures and concepts are too different to be subsumed under one general theory. One worry is that in biological evolution transmission is always “vertical,” from parent to offspring, but in processes like conceptual evolution there is “horizontal,” cross-lineage transmission. Hull replies that this sort of cross-lineage transmission does occur in nature, in particular among bacteria and viruses as well as throughout the plant kingdom (Hull 2001: 34). A second worry is that cultural and conceptual change occurs much more rapidly than evolutionary change. But as Hull notes, bacterial and viral evolution can occur much faster than much cultural or conceptual change. A third worry is that intentionality is a fundamental part of cultural and conceptual change, but not evolutionary change. But Hull sees intentionality in the “artificial selection” of the breeders (Hull 2001: 37). But sexual selection similarly introduces intentionality into selection.
Darwin thought the struggle for mates important enough to include it in his title for his book on human descent. Its significance is partly in the fact that it is “intentional.” Where female choice drives sexual selection, the beliefs, desires and preferences of the female help determine the outcome of selection and of evolution. Evolutionary psychologist Geoffrey Miller has recently revived sexual selection, using it to explain a variety of human phenomena. Miller explains this intentionality of sexual selection:
… We were neither created by an omniscient deity, nor did we evolve by blind, dumb natural selection. Rather our evolution was shaped by beings intermediate in intelligence: our own ancestor, choosing their sexual partners as sensibly as they could. We have inherited both their sexual tastes for warm, witty, creative, intelligent, generous companions, and some of these traits that they preferred. (Miller 2000: 10)
The details of Miller’s account are beyond the scope of this paper, but we should recognize in it a naturalism that represents both a return to Darwin’s pluralism, and a recognition of intentionality in biological evolution.
Before we go further though, a caution is in order. Dennett, Dawkins and Hull have all argued that selection processes are fundamental, general features of the world, and should be understood to apply beyond narrow biological evolution. This should not be confused with the use of a selection based model that is not just an instance of a more general selection process. We could for instance, think about the “survival” of theories, but without invoking a general theory of selection. Karl Popper and Thomas Kuhn both seem to be doing this. Popper, for instance, claims that his falsificationist model of science is based on “Darwinian selection” (Popper 2002: 194). And at the end of his Structure of Scientific Revolutions, Kuhn argues that science proceeds by revolution, and that,
… the resolution of revolutions is the selection by conflict within the scientific community of the fittest way to practice future science. The net result of a sequence of such revolutionary selections, separated by periods of normal research, is the wonderfully adapted set of instruments we call modern scientific knowledge … . (Kuhn 1970: 172–3)
Neither Popper nor Kuhn seem interested in incorporating theory fitness and selection into a more general theory of selection. Rather than instances of a universal selection process, these seem to be mere models of selection.
A third area of significance here is in the conception of value. Ethicists have long argued over the nature of value. Often it is conceived in terms of non-natural, secondary or supervenient properties (Richards 2005: 271–3). In these terms “goodness” is usually conceived as a property of an action, person or state of affairs. Darwin did not develop a general evolutionary theory of value, but he did provide the resources for thinking about value naturalistically – as a relation between an organism and an environment. The basic value concept for Darwin was “fitness.” One version applies to survival: an organism is better than another in some way if its traits provide a better fit with its environment so as to function better. Another version applies to reproduction: an organism is better than another in some way if its traits provide a better fit with the preferences of its potential mates so as to reproduce better.
In Richards (2005) is a Darwinian framework for thinking about these notions of fitness. The basic idea begins with mattering: A feature of an organism can matter in an environment in an indefinite number of ways and relative to survival and reproduction. Value is generated by this mattering. But mattering is complex: A feature may be good relative to one organism, but bad relative to another. It may be good relative to one respect, but bad to another. And it may be good relative to one environment, but bad to another. This can be represented in a simple valuation schema: w is good (or bad) with respect to x for y in z. The significance of this schema is that it represents mattering and value as relations between an individual organism and an environment, rather than as a simple property. This implies first, that value is subjective in that it is always relative to a subject; second, that it is nonetheless objective – based on facts about functioning and mattering. This is a Darwinian conception of value first, in that it is based on fundamental Darwinian processes. Second, value is fully naturalistic and explainable in terms of the processes we observe in the world around. Third, it conforms to Darwin’s continuity principle, applying both to humans and nonhuman species.
Part of the legitimate philosophical impact of Darwinism is its historical metaphysics. Darwin gave us the resources to think about the things in the world that change and the processes that cause change. Darwinism can therefore be seen as challenging the metaphysical picture we got first from Parmenides and Plato, that valued the unchanging “essences” over the changing. While Darwin was not the first or only thinker to focus on change, surely he was one of the most successful, and surely this success is partly a consequence of his naturalistic approach. This success of Darwinian naturalism is apparent in contemporary evolutionary approaches to human psychology, and the functioning of humans in their environment – “human social ecology.” These are the topics of the next section.
In the Descent of Man, Darwin treated the emotions and “higher” faculties – reason and the moral instincts – naturalistically and as continuous with the same faculties in other species. Human reason and sympathy, for instance, were explained on the same principles as canine reason and sympathy. As we might expect, given his naturalism, he also looked to the brain and nervous system as the physiological basis for human psychology. The most important fact for Darwin was that behavior, the brain and nervous system are all products of evolutionary processes – natural selection, sexual selection, inheritance and the effects of the environment, etc. We can then understand human psychology by understanding how a feature conferred a survival or reproductive advantage; how a feature was inherited from evolutionary ancestors; or how a feature was acquired through interaction with an environment.
Darwin began his inquiry into the higher, intellectual faculties with the assumption that they are adaptations that confer a survival and reproductive advantage (DM: 159). More recent approaches, from the pragmatists to contemporary philosophers of biology and brain scientists, typically begin with the same basic assumption, leading to Darwinian accounts of epistemology, ethics and aesthetics. The basic idea is that the capacities associated with the acquisition of knowledge, the norms and standards of good behavior, and the creation and appreciation of art, are understandable in terms of the advantage they confer for survival and reproduction.
Michael Ruse applies this idea to epistemology – the study of knowledge. He takes scientific knowledge as a paradigm instance of knowledge, then argues that scientific knowledge is a product of “epigenetic rules” or developmental tendencies.
… In order to understand why science is as it is – why laws, why predictions, why falsifiability, why consiliences – we need to look at the principles of scientific reasoning or methodology… . What I argue is that these principles have their being and only justification in their Darwinian value, that is in their adaptive worth to us humans – or at least to our proto-human ancestors. In short, I argue that the principles which guide and mould science are rooted in our biology, as mediated by our epigenetic rules. (Ruse 1998: 155)
Ruse argues for a Darwinian explanation of the developmental tendencies that cause us to think in terms of scientific law, to value predictions, to demand falsifiability, and to look for consilience in our reasoning (Ruse 1998: 164–8).
Ellen Dissanayake has similarly argued that the capacities and tendencies underlying our appreciation and construction of art are to be understood on a Darwinian basis. The adaptive value in art behavior is its ability to make things “special.” This ability to make things special is a general enabling mechanism, based on the motivational force of pleasure, and directed towards activities associated with survival and reproduction.
The principal evolutionary context for the origin and development of the arts was in activities concerned with survival. As we look back through the eons, we see abundant evidence of humans making things or experience special. Overwhelmingly what was chosen to be made special was what was considered important: objects and activities that were parts of ceremonies having to do with important transitions, such as birth, puberty, marriage, and death; finding food, securing abundance, ensuring fertility of women and of the earth; curing the sick; going to war or resolving conflict; and so forth. (Dissanayake 1992: 61)
While survival and reproduction enhancing activities have been the focus of this “making special,” Dissanayake argues that the same capacities and tendencies can be directed to other types of activities, and explain the pervasiveness of art.
Ruse, Dissanayake, and many other contemporary thinkers have focused almost exclusively on natural selection. Geoffrey Miller, however, sees potential explanations of a variety of human phenomena, including the arts, in sexual selection, and based on the idea that some behaviors are “fitness indicators.” The selection of a mate that has these fitness indicators guarantees fit offspring. And the sorts of traits that indicate fitness are also those that function in the arts. This avoids the problem that,
… Nobody has been able to suggest any plausible survival payoffs for most the things that human minds are good at, such as humor, story-telling, gossip, art, music, self-consciousness, ornate language, imaginative ideologies, religion, and morality. How could evolution favor such apparently useless embellishments? (Miller 2000: 18)
If Miller is right about all this, he is giving a Darwinian account that supplements the evolutionary epistemology and aesthetics of Ruse and Dissanayake.
We can be Darwinian not just in our explanations, but also in our conceptions of psychological states, faculties and capacities. Recently, philosophers and neuroscientists have argued for an approach to conceiving human psychology based on evolutionary functions (not to be confused with the non-evolutionary “functionalism” in recent cognitive psychology and philosophy of mind). Emotions are conceived functionally by the philosopher Paul Griffiths, who describes them as “affect programs,” comprised of a coordinated system of responses, physiological, muscular-skeletal, and expressive (Hodge and Radick 2003: 91). The neuroscientist Joseph LeDoux similarly advocates a functional conception of the emotions.
I view emotions as biological functions of the nervous system … This approach contrasts sharply with the more typical one in which emotions are studied as psychological states, independent of the underlying brain mechanisms. Psychological research has been extremely valuable, but an approach where emotions are studied as brain functions is far more powerful. (LeDoux 1996: 12)
The functional concepts of Griffiths and LeDoux contrast with more traditional conceptions of the emotions based on feeling, cognition or perception.
Another kind of explanation used by Darwin was in terms of evolutionary ancestry or phyletic conservativism. Many of the features of an organism are present not because of natural selection, but because of inheritance from an ancestor. Humans for instance, have vertebral columns not because of some direct adaptive advantage to humans, but because their ancestors had a vertebral column. Similarly the human brain is a product of the pre-human evolutionary past, and the specifically human functioning is built upon the functioning of evolutionary ancestors. This is largely a process of addition rather than modification. Neuroscientist David Linden explains:
The brain is built like an ice cream cone … Through evolutionary time, as higher functions were added, a new scoop was placed on top, but the lower scoops were largely unchanged. In this way, our human brainstem, cerebellum and midbrain are not very different in overall plan from that of a frog. It’s just that the frog has only rudimentary higher areas in addition (barely more than one scoop). All those structures plus the hypothalamus, thalamus and limbic system are not that different between humans and rats (two scoops), which have a small and simple cortex, while we have all that plus a hugely elaborated cortex (three scoops). When new, higher functions were added, this did not result in a redesign of the whole brain from the ground up; a new scoop was just added on top. Hence, in true kludge fashion, our brains contain regions, like the midbrain visual center, that are functional remnants of our evolutionary past. (Linden 2007: 21–2)
The fact that humans have functional remnants of their evolutionary past seems to vindicate Darwin’s continuity principle – we share brain structure with other species so we can explain our psychologies similarly – but it also has philosophical implications.
The fact that newer brain structures and faculties were just layered upon old structures and functions has several consequences. The first is that there are multiple parallel networks: Older networks pass through the emotion, memory and motor systems but not through the newer regions of the cortex associated with consciousness. Newer networks also pass through the newer “conscious” regions of the cortex. Significantly, the older systems are typically faster, so we can get sensory input processed by the emotion centers in the amygdala, and memory centers in the hippocampus, and have motor output and action before we are even consciously aware of the sensory input. A sensory experience, therefore, may produce a particular emotional response and an action prior to and without conscious awareness or reason. Neuroscientist Michael Gazzaniga tells us that “by the time any of us consciously experience anything the brain has already done its work” (Gazzaniga 2006: 89). This implies that conscious deliberation often plays a role only in inhibition – stopping an action in its early stages. As Gazzaniga describes it, we may not have free will here, but we might have “free won’t” (Gazzaniga 2006: 93). The philosophically important point of all this is that the causal sequence of psychological events may often not involve conscious deliberation at all, or only after the fact. If so, it is unclear that self-conscious introspection can have access to the true causal picture.
Recent experiments with split brain patients indicate that there is another barrier to our abilities to understand psychological functioning through introspection, based on the presence of a system in the left cortex that constructs narratives to explain actions – after the fact. Patients with severe epilepsy sometimes have surgery to cut the corpus callosum and anterior commissure that connect the left and right hemispheres of the brain. This surgery leaves each side of the cortex functioning normally, but unable to communicate. It is then possible to give directions to just the right cortex, which can then initiate action without communicating the stimulus to the left side. But the left side of the cortex, responsible for speech, when asked why the action was undertaken will typically fabricate a response, instead of expressing ignorance. Linden explains:
If, in a split-brain patient, the (mute) right brain receives the instruction “Go take a walk,” the subject will push the chair back and prepare to leave. If, at that point, the (speaking) left brain, which had no access to the instruction, is asked “What are you doing?” it will manufacture a seemingly coherent response to make sense of the body’s action, such as “I was feeling thirsty and decided to get a drink” or “I had a cramp in my leg and needed to work it out.” This is not just of fluke of one or two split-brain patients. The narrative-constructing capacity of the left cortex has now been clearly observed in more than 100 split brain patients in many different situations. (Linden 2007: 229)
Linden claims this narrative functioning is at work in dreaming and religious belief as well. But the important point here is that we may all be constantly subject to the misleading narration of this “confabulator,” or “baloney generator” as Steven Pinker calls it.
The spooky part is that we have no reason to think that the baloney-generator in the patient’s left hemisphere is behaving any differently from ours as we make sense of the inclinations emanating from the rest of our brains. The conscious mind – the self or soul – is a spin doctor, not the commander in chief. (Pinker 2002: 43)
If Pinker and Linden are right, then our own psychology may not just be inaccessible to us in important ways, but we may in fact be systematically mislead by our own accounts.
The philosophical significance of this understanding of brain function has not been explored in detail, so it is hard to be very precise here. There are, however, some fairly obvious ways that it might impact philosophy. First, it challenges the view, usually associated with Descartes, that the operation of the mind is transparent and discoverable by introspection. But the implications go further, suggesting that introspection may actually be misleading. The left-brain “baloney generator” tells a satisfying but incorrect story of motivations and causes. Second, this approach also challenges the view that for humans, reason plays a primary causal role in action and reaction – we do things as a result of conscious deliberation about principles or means and ends. Human psychology instead seems to be based on an animal foundation that functions to a significant degree independently of conscious deliberation and reason.
Rather than focusing on individual psychology, a Darwinian approach might also begin with social ecology – the study of humans in a social environment. Owen Flanagan does this in his approach to ethics.
As I conceive it, normative ethics is part of the science of ecology. Ecology is the discipline that tells us what conditions lead to the flourishing of various natural systems (wetlands, orchids, beavers) in certain environments. Ethics is ecology for humans and other sentient beings. Ethics, so conceived, is both empirical and normative. It asks: what are the conditions that led to fitness and flourishing for humans and other sentient beings? To answer, we need to look and see what sorts of environments lead to flourishing and what don’t. (Hodge and Radick 2003: 381)
Flanagan sees this as a Darwinian approach in that it is naturalistic and appeals to selection processes (Hodge and Radick 2003: 381). He begins by quoting a long passage from Darwin’s Descent of Man.
In order that primeval men, or the ape-like progenitors of man, should have become social, they must have acquired the same instinctive feelings … They would have felt uneasy when separated from their comrades, for whom they would have felt some degree of love, they would have warned each other of danger, and have given mutual aid in attack or defense. All this implies some degree of sympathy, fidelity, and courage … The love of approbation and the dread of infamy, as well as the bestowal of praise or blame, are primarily due … to the instinct of sympathy, and this instinct no doubt was originally acquired, like all the other social instincts, through natural selection … With increased experience and reason, man perceives the more remote consequences of his actions, and the self-regarding virtues, such as temperance, chastity, &c., which during earlier times are … utterly disregarded, come to be highly esteemed or even held sacred … Ultimately a highly complex sentiment, having its first origin in the social instincts, largely guided by the approbation of our fellow-men, ruled by reason, self-interest, and in later times by deep religious feelings, confirmed by instruction and habit, all combined, constitute our moral sense or conscience. (Hodge and Radick 2003: 383)
There are three important ideas here: the moral sentiments and instincts, the “approbation of fellow-men,” and “religious feelings.”
The moral sentiments, according to Darwin, are based on the sympathy humans have for, and pleasure they get from the company of their conspecifics. We need and enjoy the company of other humans, and we “feel their pain.” This social nature is likely a product of our evolutionary past. As primatologist Frans de Waal has persuasively argued, our closest primate relatives seem to have the same social sentiments and preferences, and enjoyment of conspecifics that we see in humans (de Waal 2006). What is important here is that we are moral because we have in our nature certain emotions and preferences. We are not moral just on the basis of our reason or ability to form maxims that guide our actions. As Flanagan argues, emotions are “essential to morality, even when experience, habit and reason enter the picture” (Hodge and Radick 2003: 384).
But emotion, habit and reason are not enough for Flanagan. Morality requires norms, and norms presuppose evaluations. This is the approbation component of morality. Flanagan explains:
… Norms – moral ones, at any rate – express evaluations and make appeals that certain practices creating protecting or maintaining what is valuable to be observed. When I display anger, I express a desire that you back off. If you get the message you will do so, and if you are smart you will continue to do so in relevantly similar situations. Supposing you do so, you now govern your behaviour by a norm, consciously or unconsciously. (Hodge and Radick 2003: 385)
For Flanagan, moral expressions and associated judgments function to guide behavior. When a parent gets angry at a child and tells him that what he did was wrong, the parent is trying to get him to act in accordance with a particular norm – one that rules out the behavior that produced the disapproval. Flanagan sees this as a fitness enhancing move:
The Darwinian genealogy of morals I am sketching ties the origin of morality very closely to Darwinian fitness. A basic emotional expression communicates the wish that others behave in certain ways, ways that will promote the survival and reproductive success of the expressor. (Hodge and Radick 2003: 386)
This idea that we can understand moral judgments in light of their evolutionary functioning to guide behaviors has also been developed by Richard Joyce. First, he allows that it is not the actual behavior that would be adaptive, but the underlying psychological tendencies. So it is not particular moral judgments that function to enhance survival, but the tendency to make moral judgments. What is important for Joyce is that moral judgments have practical clout: “Calling an action ‘morally correct’ or ‘virtuous’ or ‘wrong’ or ‘just’ is (putatively) to draw attention to a deliberative consideration that cannot be legitimately ignored or evaded” (Joyce 2006: 57–8). This practical clout functions as motivation – “probabilifying” action: “a moral judgment in favor of an action is no guarantor that the action will be performed, but so long as it increases the likelihood of the performance then this may be its evolutionary function” (Joyce 2006: 114).
According to Joyce, moral judgments motivate in a special way, coordinating the actions of both the person making the moral judgment and the person who hears it. First, the expression of approval commits the expressor to a particular attitude that motivates that person’s action. For instance, if a person publicly claims that “recycling is morally required,” or that “premarital sex is forbidden,” then that public commitment motivates that person to act in accordance with the norm expressed. And it likewise serves as a motivator for the person who is the target of the moral judgment. This bridging function produces a coordination of norms and behavior:
… We should now see that one of the adaptive advantages of moral judgment is precisely its capacity to unite these two matters. By providing a framework within which both one’s own actions and others’ actions may be evaluated, moral judgments can act as a kind of “common currency” for collective negotiation and decision making. Moral judgment thus can function as a kind of social glue, bonding individuals together in a shared justificatory structure and providing a tool for solving many group coordination problems. (Joyce 2006: 117)
In the last sentence here, Joyce raises an important question to be asked of a Darwinian framework – the justification of moral judgments. Moral judgments won’t serve their function to coordinate behavior if they are not regarded as expressing more than mere preference. Joyce argues that we have this tendency to objectify moral facts from a young age, treating some judgments as expressions of mere preference, and others as independent of preferences. If so, there must be some fundamental feature of human psychology, based on an emotional response, that treats some kinds of judgments as independent of preference and with special normative force (Joyce 2006: 128–30).
Michael Ruse has also addressed this question of normative force and given it an evolutionary explanation. According to Ruse, evolution has made us such that we naturally cooperate. And to make us cooperate better, we have acquired the attitude that moral prescriptions are not mere preferences or conditional requirements, but obligations: “Epigenetic rules giving us a sense of obligation have been put in place by selection, because of their adaptive value” (Ruse 1998: 223). The belief that moral principles have special authority, perhaps from God, is one, but not the only way for this to function. Ruse describes this as the illusion of ethics.
The Darwinian argues that morality simply does not work (from a biological perspective), unless we believe that it is objective. Darwinian theory shows that, in fact, morality is a function of the (subjective) feeling; but it shows also that we have (and must have) the illusion of objectivity. In other words, we ‘objectify’ moral claims … The point about morality (says the Darwinian) is that it is an adaptation to get us to go beyond regular wishes, desires and fears, and to interact socially with people. How does it get us to do this? By filling us full of thoughts about obligations and duties, and so forth. And the key to what is going on is that we are then moved to action, precisely because we think morality is something laid upon us … In a sense, therefore, morality is a collective illusion foisted upon us by our genes. (Ruse 1998: 253)
This passage may seem shocking and dangerous. But if Ruse is right, then that would be expected. Evolution has made us so that we cannot regard our moral principles as anything less than objective.
This conclusion gestures toward what might be regarded as a useful function for Darwinism in philosophy – as the foundation of an “error theory.” If Darwinian approaches can tell us why we think the way we think about topics central to philosophy – knowledge, ethics and human nature, perhaps it can also tell us where we tend to go wrong, and why. The preceding discussion has suggested several ways that Darwinism can unmask typical errors. First, the fact that much of psychological functioning occurs subconsciously in the older parts of the human brain, prior to conscious deliberation and introspection implies that we typically cannot understand the causes of our own action by introspection. Second, the functioning of the left-brain confabulator suggests that the story we tell ourselves may be positively misleading. Third, the account of the functioning of norms and moral judgments we get from Flanagan and Joyce suggests that at least sometimes a focus on the content of the norms – what they value or disvalue, has missed what is important – the functioning of norms and judgments to guide and coordinate behavior. Finally, the special normative force that we associate with ethical principles seems to get “explained away” as an illusion favored by evolution, an illlusion that gets us to act in certain ways. The philosophical implications of all this have yet to be worked out with care, so I will not try to draw a specific conclusion, but surely any philosophical view that makes assumptions about human psychology or social ecology should revisit those assumptions in light of this Darwinian error theory.
Darwin’s philosophical impact begins with his commitment to a methodological naturalism and explanatory pluralism, and how that has played out relative to philosophical discussions and issues. From Humboldt, Darwin took the view that nature is interconnected and that humans are part of, and continuous with nature. From Herschel and Lyell he adopted the empiricist requirement that causes be directly observed and be to the degree observed. And from Whewell he adopted the view that a good explanation unifies phenomena. Finally, Darwin adopted an explanatory pluralism that may have emphasized natural selection, but also incorporated sexual selection and phyletic conservativism, as well as a variety of other processes.
This naturalism has obvious philosophical impact in the commitments of the pragmatists, who argued that we can understand doubt, inquiry, meaning and truth on a Darwinian approach. Its impact is also obvious in the naturalistic and historical metaphysics that conceives of species as “historical individuals” rather than natural kinds with essences, and views selection as a general process for generating order. Perhaps less obvious in terms of philosophical impact, Darwinism has provided the resources to understand the functioning of human psychology in terms of evolutionary history and the selection processes that formed the human brain. And it has also provided a naturalistic framework for thinking about ethics as a natural feature of human social behavior in an environment – as “human social ecology.” On the basis of its insights into human psychology and social ecology, the Darwinian approach has also seemed to promise an understanding of the processes at work in our acquisition of knowledge, and in our use of moral judgments and belief in their normative force. Finally, Darwinian naturalism suggests a naturalistic “error” theory that might tell us ways we are likely to go wrong in our philosophical thinking about reason, emotion and moral principles.
There are, however, two enduring philosophical concerns about Darwin’s naturalistic approach. First is a concern about its continuity thesis that humans are to be understood on the same explanatory principles as other species. The concern is that humans are so different from other species that it becomes a difference “in kind,” requiring a different kind of explanation. Christine Korsgaard expresses this concern:
… Kant speculated that the form of self-consciousness that underlies our autonomy may also play a role in the explanation of some of the other distinctively human attributes – including culture, romantic love, and the capacity to active from self-interest. Other philosophers have noticed the connection of self-consciousness of this sort of capacity for language. I can’t go into those arguments here, but if they are correct they would provide evidence that only humans have this form of self-consciousness … If that is right, then the capacity for normative self-government and the deeper level of intentional control that goes with it is probably unique to humans beings. (de Waal 2006: 116)
The idea is that because of the distinctive human functioning based on selfconsciousness, we should explain human behavior in terms of things like principles, values and ideas, rather than emotion and instincts.
A form of life governed by principles and values is a very different thing from a form of life governed by instinct, desire and emotion – even a very intelligent and sociable form of life governed by instinct, desire and emotions …We have ideas about what we ought to do and to be like and we are constantly trying to live up to them. Apes do not live in that way … Even if apes are sometimes courteous, responsible and brave, it is not because they think they should be … . (de Waal 2006: 117)
If Korsgaard is right, the proper way to explain human behavior is unique to humans, and Darwin’s continuity principle fails.
The Darwinian has obvious responses to Korsgaard’s exemptionalist objection. The first is that modern science has proven Korsgaard’s Kantian assumptions wrong about both human and ape psychology. Humans are not as governed by self-consciousness and intentional control as claimed, while apes are not as different from humans as claimed. Korsgaard’s claims are, after all, empirical and must be backed up by evidence. Unfortunately the best evidence is against them. The second response is based on the fact that Darwinian metaphysics does not recognize the “differences in kind” assumed by Korsgaard and others. While humans may differ from other species in dramatic and significant ways, because there is common ancestry and gradual divergence the differences are still only of degree. And if the basic units of biodiversity and evolution are “historical individuals” rather than natural kinds, then it is unclear that there can be essential differences in a metaphysically significant way. Korsgaard and the Darwinians seem to be starting from fundamentally different metaphysical stances.
The second concern is about naturalism and the commitment to a ‘scientific’ approach: doesn’t the Darwinian approach just rule out by fiat, non-naturalistic explanations that may in fact be better? Alvin Plantinga expresses this worry from a theistic standpoint:
… It could be that the best scientific hypothesis was evolution by common descent – that is, of all hypotheses that conform to methodological naturalism, it is the best. But of course what we really want to know is not which hypothesis is the best from some artificially adopted standpoint of naturalism, but what is the best hypothesis overall. (Plantinga 1998: 694)
Plantinga makes it clear that he thinks the best explanation is likely to be of a non-natural sort – an explanation in terms of God (Plantinga 1998: 695).
One need not be a theist like Plantinga, however, to reject the naturalistic restriction of Darwinism. Korsgaard also seems to be rejecting the naturalistic approach in favor of an “intentional” approach based self-conscious reasons, principles and a “deeper level of intentional control.” For those, like Korsgaard, who think human behavior is to be explained in terms of unique human intentions, Darwin’s naturalism is simply the wrong approach.
It may be that ultimately, the Darwinian cannot refute Plantinga or Korsgaard. But what the Darwinian can do is to appeal to the explanatory power of science in general. If we take a scientific approach seriously in other domains of inquiry, why would we not apply it to human psychology, social ecology and inquiry? And the Darwinian can also appeal to the explanatory power of science relative to the phenomena discussed here. Does it successfully explain human inquiry, cognition and ethical behavior? The ultimate philosophical significance of Darwinism may well be in the foundation it provides for a naturalistic, “scientific” alternative to recent philosophical approaches based on the primacy of reason, linguistic practices and self-conscious introspection. In this sense, Darwinism is in part a return to an older approach that saw what we would now call science as “natural philosophy,” and conceived it as just another branch of philosophy. On this approach, we use whatever resources we have, be they scientific, logical or linguistic, to understand the philosophical aspects of human nature. Surely there are good reasons to use a scientific, Darwinian naturalism to answer our philosophical questions, and illuminate our philosophical practices.
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The authoritative biography of Darwin’s life during and after the publication of his Origin is J. Browne, Charles Darwin: The Power of Place (Princeton, NJ: Princeton University Press, 2002). The authoritative biography of Darwin’s life up to the writing of the Origin is J. Browne, Charles Darwin: Voyaging (Princeton, NJ: Princeton University Press, 1995). M. Ereshefsky (ed.) The Units of Evolution (Cambridge, MA: Bradford Books, 1992), is an edited volume containing essays about the nature of species from important systematists and philosophers of biology. M. J. S. Hodge and G. Radick (eds) The Cambridge Companion to Darwin (Cambridge, Cambridge University Press, 2003), is an edited volume covering a variety philosophical and historical topics relating to Darwin and his development to modern Darwinian metaphysics, epistemology, and ethics. A philosophically sophisticated, evolutionary account of moral judgment and behavior can be found in R. Joyce, The Evolution of Morality (Cambridge, MA: Bradford Gooks, 2006). R. J. Richards, Darwin and the Emergence of Evolutionary Theories of Mind and Behavior (Chicago: University of Chicago Press, 1987), offers an authoritative, historical account of biological accounts of mind and behavior from the seventeenth and eighteenth centuries to Darwin and beyond to the twenty-ninth century. A careful historical and philosophical account of the “Darwinian Revolution,” by the most prominent philosophical expert on Darwin is M. Ruse, The Darwinian Revolution: Science Red in Tooth and Claw (Chicago: University of Chicago Press, 1999), and Ruse’s Taking Darwin Seriously: A Naturalistic Approach to Philosophy (Amherst, NY: Prometheus Books, 1998), sympathetically explores the implications of Darwin for philosophy.