I. Introduction
II. Aristotle
A) Aristotle: Teleology versus Mechanistic
B) Chance
C) Vitalism
D) Aristotle's Legacy
III. Buffon and Time
IV. Natural Theology
V. Lamarck and Natural History
VI. Charles Darwin
A) The Transformation
B) Biologists' Responses to Teleology
C) Theory of Evolution
D) Natural Selection
VII. Conclusion
VIII. References
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The desire to understand organisms has been the driving force of biology since its conception as a science. Aristotle and Charles Darwin are arguably two of the most influencial biologists of all time. Aristotle's teleological approach to biology was followed for over 2,000 years. One biologist believes that Aristotelian teleology "has been the ghost, the unexplained mystery which has haunted biology through its whole history" (Ayala, 10). If Aristotle's approach has haunted biology, then Darwin, who nicknamed himself the "Devil's Chaplain," and his idea of natural selection has exorcised Aristotle's ghost. While Aristotle explained biology through order and purpose, Darwin argued that it was chance and chaos that is accountable for the living world as we know it. Guiseppe Montalenti, an Italian geneticist and philosopher of biology, wrote that Darwin's ideas were a "revolt against thinking in the Aristotelian-scholastic way" (Ayala, 4). In order to understand how Darwinism can be classified as a revolt against Aristotle, we must first examine Aristotle's biological ideas.
Before Aristotle, Democritus was a leading philosopher of biology. In addition to being a reaction against Aristotle's ideas, Darwin's revolutionary ideas solved the debate between the mechanist philosophy of Democritus and the teleological philosophy of Aristotle. To Democritus, form and movement of atoms were the ultimate causes of living things. Democritus used a mechanistic hypothesis based on the structure and movement of atoms to try to explain life. Aristotle rejected this mechanistic approach because he believed that necessity and chance alone cannot plausibly explain the harmony of the world, or the final causes (Ayala, 7). Aristotle supported this rejection by arguing that if, as Democritus believed, "configuration and colors constitute the essence of various animals and of their several parts," how can it be explained that "a dead body has the same configuration as a living one"? (P.A. 641a)
In order to explain the harmony and final causes of the world, Aristotle used teleology, the study of the purpose of nature. Aristotle believed that biologists should "follow the plan adopted by mathematicians in their astronomical demonstrations, and after considering the phenomena presented by animals, and their several parts, proceed subsequently to treat of the causes and the reason why" (P.A. 639b). Using this plan, Aristotle constructed causes for body parts and processes of the body, such as the different types of teeth. Aristotle explained the process used to describe organisms in An. Post. 89b 37: "' when we have ascertained the thing's existence, we inquire as to its nature...when we know the fact we ask the reason" (Evans, 82).
Despite his frequent use of teleological explanations, Aristotle did warn against teleology leading to misinterpretations of facts. In a passage about the reproduction of bees in the Generation of Animals, Aristotle worried that there are insufficient observations on the matter, and warns that his theory is contingent on future facts supporting the theory. One twentieth century biologist believes that Aristotle did not take his own advice enough. Ayala wrote that Aristotle's "error was not that he used teleological explanations in biology, but that he extended the concept of teleology to the nonliving world" (56).
Perhaps Aristotle used teleology so frequently because order and purpose, in the universe and in life, were very important to him. Aristotle thought it was inconceivable that chance, which is not connected with purpose, could be used to explain biological occurrences. In Phys. 196a 19-24, he criticized Empedocles for the use of chance to describe biological occurrences. And in the Parts of Animals 640b, Aristotle wrote that, "Empedocles, then, was in error when he said that many of the characters presented by animals were merely the results of incidental occurrences during their development."
Aristotle was a vitalist, and this philosophy had a strong influence on his writings. His vitalistic beliefs are described in On the Soul and On the Generation of Animals. These beliefs can be summarized into four main traditions of Aristotle's vitalism:
1. He identifies the life of an organism with its psyche
2. He finds purposefulness and organic unity as the most important aspects of vitalism
3. He argues that the whole form, rather than body parts, should be taken into account
4. He describes that the soul is the final cause
Given these four traditions, it is not surprising that Aristotle thought that a description of matter, such as a limb, was not a good description of organisms, just as a house is not described as bricks and mortar. Individual variability was not important and was seen by Aristotle as due to "necessity." Rather than focus on individual variability and individual parts, Aristotle thought it was proper to focus on the "final cause" of the whole organism. Aristotle believed that "soul" was probably the final cause, as is evidenced by this passage from Parts of Animals: "now it may be that the form of any living creature is soul, or some part of soul, or something that involves soul" (641a, 18).
Aristotle's traditions and ideas continued until long after his death. There was a rediscovery of Aristotelian philosophy in the twelfth and thirteenth centuries, and the Aristotelian system was incorporated into Christian philosophy by St. Thomas Aquinas. There was a breakdown of the Aristotelian system during the Renaissance when the scientific revolution revealed that the earth is no longer the center of the universe. However, Aristotle's biological theories were not affected by this breakdown. This does not mean that all people still accepted Aristotle's ideas during the Renaissance. In fact, one twentieth century scientific philosopher, Mayr, blames Aristotle's teleology of the nonliving world for the rejection of Aristotle by Bacon and Descartes. Bacon and Descartes rejected "the existence of a form-giving, finalistic principle in the universe" and thought this rejection necessitated the elimination of all teleological language -- even biology (Mayr, 38).
Biologists were forced to reexamine their concept of living things when the discovery of time was made in the eighteenth century. With the exception of the cosmogonies of Heraclitus and Lucretius, most ancient cosmogonies described a static world. Once Buffon reconstructed geological history into a series of stages, biologists and deists alike had to account for this new knowledge that the earth was older than originally thought. The field of palaeontology was developed to help understand the evolution of the earth. The knowledge gained from palaeontology and reformed geology was necessary to the development of the evolutionary argument. Deists provided a new explanation for the creation of the world. They explained that God created the world and then gave it a set of laws that guide the world into perfection (Mayr, 57).
This explanation helped stabilize religion. By the mid-nineteenth century, physics and chemistry were used to explain phenomena, such as gravity, that were previously associated with religion. People still felt secure with their religious views because they accepted the above deist explanation of the earth's history and because biological occurrences were still explained in association with a creator. Religion in the English Protestant Church was verified through "Natural Theology" -- the "demonstration of the goodness of God by the contemplation of nature and the benevolent artifice which seemed everywhere to demonstrate" (Burrow, 17). The Church at this time, the Victorian Era, was very strong. The Christian tradition was thriving in this age of control and reason.
The only dissent from the strict Victorian Era was from Lamarck. In 1809 Lamarck published Philosophie Zoolique, in which he proposed that organisms gave rise to new organs when necessary and that these new organs were passed on to their offspring. Lamarck's theory of evolution included the two main principles that 1) there is an internal drive towards progress and 2) that there is an inheritance of acquired characteristics (Ayala, 9). Lamarck's theory brings to mind Empedocle's theory of evolution. According to Aristotle, Empedocles believed that, "Wherever, then, everything turned out as it would have if it were happening for a purpose, there the creatures survived, being accidentally compounded in a suitable way; but where this did not happen, the creatures perished" (Phys. B8, 198b29 in Kirk, et. al., 304).
The study of natural history became immensely popular in the early nineteenth century. Exploring nature was seen as a way to explore the Creator and Natural Theology. Such exploration was easy for any person to perform, unlike exploring astronomy, which required knowledge of mathematics. Anyone could examine trees or birds. The immense popularity of studying natural history is evidenced by the fact that the initial printing of 1,250 copies of the Origin of the Species sold out in one day (Burrow, 19).
Among the people enthralled with natural history was the Englishman Charles Darwin. After several career changes, Darwin decided to become a naturalist. In 1831 he began a position as a naturalist on the H.M.S. Beagle, an exploration ship that needed a naturalist to keep a record of the ship's biological findings. When he began this voyage, Darwin shared the popular belief that each species was created to suit its environment and that there was harmony in nature (part of Natural Theology). By the time he returned to England five years later, Darwin's view of nature had changed. He still believed that there was harmony in nature, but he no longer believed in perfect adaptation. Instead, Darwin believed in the transmutation (idea that each species is descended from other earlier species and that characteristics are inherited) of the species.
Darwin's philosophy changed because of his experiences on the Beagle. He kept very detailed records of the organisms encountered. After examining his notes on extinction, distribution of species and the utility of organs, Darwin concluded that perfect adaption is not an appropriate explanation for the diversity of life. Particularly troublesome to Darwin were the slight variations from island toisland of the Galapagian tortoises and finches. Darwin began to believe in transmutation, though he was not completely comfortable with the idea. In a letter to Hooker in 1844 Darwin wrote: "'I am almost convinced (quite contrary to the opinion I started with) that species are not (it is like confessing to murder) immutable'" (Burrow, 32). To alleviate his trepidation, Darwin sought an explanation for his new belief.
Darwin's transformation occurred during a time when many naturalists were beginning to reject the teleological approach to explaining biological occurrences. One biologist,Sir Thomas Henry Huxley, felt that renewed interest in evolution was going to be the death of teleology. He wrote that "'The doctrine of evolution is the most formidable opponent of all the common and courser forms of Teleology...The Teleology which supposes that the eye, such as we see it in man or one of the higher vertebrata, was made with the precise structure it exhibits, for the purpose of enabling the animals which possesses it to see, has undoubtedly received its death blow'" (Ayala, 228). Huxley then continued to say that evolution did not completely eradicate teleology as a method to explain the universe.
Darwin also realized that the teleological approach was contrary to his views, so he attempted to shed doubt on the ideas of a fixed relationship between an organism and its environment, along with the functional necessity of every aspect of an organism (Ospovat, 29). One example of Darwin's argument against teleology involves flightless, though winged, beetles. Darwin argued that these beetles cannot be explained through teleology and creation because "'if simple creation, surely it would have [been] born without them [the wings]'" (Ospovat, 26).
Even with his rejection of teleology, Darwin still very much respected its greatest proponent, Aristotle. Aristotle is mentioned in the opening paragraph of theOrigin of the Species and in a letter to William Ogle , Darwin praises Aristotle's pioneering work and recognizes his important role in the development of now common knowledge. Though Darwin began to reject teleology, he still was unsure of the roles of chance and purpose. In 1860, he wrote to Asa Gray, "'I cannot think that the world as we see it is the result of chance; and yet I cannot look at each separated thing as the result of Design...I am, and shall ever remain, in a hopeless muddle'" (Ayala, 225).
However muddled about teleology, Darwin did not think that the living world must be explained in terms of its purpose. He once posed the question, "'What would the Astronomer say to the doctrine that the planets moved [not] according to the laws of gravitation, but from the creator having willed each separate planet to move in its particular orbit?" (Burrow, 48) Here, Darwin is referring to the breakdown of the association between religion and astronomy, physics and chemistry that occurred in the Renaissance. Darwin urged the inclusion of biology as a hard science, so that, like physics and chemistry, biology would be built on the organization of knowledge based on testable hypotheses.
The theory of evolution was not formed by Darwin. Ideas of evolution were present even in Ancient Greece. Empedocles' [link previously made KRS 303] evolution theory involved the coming together of limbs, while Xenophanes thought that humans came to be "from earth and water" (Sextus, adv. math. x, 34 in Kirk, et. al., 176). Darwin's introduction to the Origin of the Species is primarily a list of previous views of evolution, and who held them. One of these predecessors was Darwin's grandfather, Eramus Darwin.
What set Charles Darwin apart from these other proponents of evolution was his theory of natural selection as the vehicle of evolution. Darwin credits the inspiration of his natural selection theory to reading T.R. Malthus' Essay on Population (1798). In his essay, Malthus attempted to demonstrate an Equilibrium Theory -- that, unless checked by famine, disease or voluntary restraint, population growth will outrun food supply. Darwin's theory was complete by the time he wrote his "Sketch of 1842," but he did not publish it for almost twenty years because he wanted to produce a large work with both his own evidence for his theory, and evidence of other naturalists (Ospovat, 1). Darwin was forced to publish his theory earlier than planned, when he learned that another naturalist, Alfred Wallace, was about to publish a similar theory (coincidentally, also inspired by Malthus' essay).
Darwin's theory completely revolutionized biological philosophy. With his theory came the recognition that the individual is the most important unit of biological change, and that this change occurs as the result of chance. In his theory Darwin proposed that there is a "Struggle for Existence." This struggle was later used in support of several arguments. British Imperialists attempted to justify their actions by arguing that according to Darwinism, the strong must overpower the weak. In the late 1800's, "Passionate Nationalism," induced members of each nationality to believe that their nation was the most "fit." And in the early twentieth century, Hitler and other Nazis used Darwin's work to support the "biological necessity" for war and survival of the fittest -- in this case, the Aryans.
Such arguments could not be supported using the biological ideas of Aristotle, since his concept of species included the idea that all individuals are alike. Individual differences, like hair color, are unimportant because they are not promoted by a final cause. However, individual differences are the cornerstone of evolution through natural selection. Without individual differences, natural selection, and therefore evolution, could not occur. For this reason, individuality is seen by biologists as the most important aspect of living organisms. Some biologists attempt to describe evolution teleologically. This is not possible, as evolution through natural selection can not be described as goal-directed since it occurs as a result of past events or mutations, not in anticipation of future events. If it were goal-directed, natural selection would not be flexible enough to be effective in environments that are rapidly changing (Mayr, 43).
Aristotle used teleology to explain biology because he could not conceive that disorder and purposelessness could give rise to order and purpose. Darwinism supports the theory that natural selection is a process that brings order out of randomness. In addition, to evolutionists, "randomness or chance does not mean that the events have no cause but that the events have no relation to the needs of the organism at the time they occur" (Ayala, 226).
One main problem that people have in accepting Darwin's theory is that his view of nature did not reveal any "clues for human conduct, no answers to human moral dilemmas" (Burrow, 43). Order, Purpose and Divine Direction are all very comforting to humans. That is one reason why Aristotle's teleological views survived for over 2,000 years. Now that Darwin has changed those views of nature, we need to answer the question "Is natural selection the only ordering process in biological evolution?" (Ayala, 227)
Ayala, F.J. and Tobzharsky, T. Studies in the Philosophy of Biology. University of California Press. Berkeley and Los Angelos. 1974.
Burrow, John. Editor introduction to Charles Darwin's Origin of the Species. Penguin Books. England. 1968.
Evans, G. The Physical Philosophy of Aristotle. University of New Mexico Press. Albuqerque. 1964.
Kirk, G., Raven, J. and Schofield, M. The Presocratic Philosophers. Cambridge University Press. Cambridge. 1983.
Mayr, E. Toward a New Philosophy of Biology. Harvard University Press. 1988.
Ospovat, D. The Development of Darwin's Theory. Cambridge University Press. Cambridge. 1981.