By Paul Draper

Book Symposium
Michael Ruse, Darwin and Design: Does Evolution Have a Purpose? (Harvard UP, 2003)

Where Does Teleological Thinking Stand Today? Reinterpreting Ruse’s Darwin and Design

Paul Draper, Florida International University

The main focus of Michael Ruse’s excellent book, Darwin and Design, is a question about biology: if Darwin’s theory of natural selection eliminates the need to understand the living world teleologically, then why does function-talk persist in contemporary evolutionary biology? The book professes to address a broader question as well, namely, where does teleological or design-like thinking stand today, in both science and philosophy? Because of its focus on evolutionary biology and not on origin-of-life theory or cosmology or philosophy of religion, the book does not provide a complete answer to this broader question, as Ruse admits in his preface. He suggests, however, that his conclusions could be reinterpreted in terms that would be pertinent to the issues he does not address. I intend to offer just such a reinterpretation here, focusing in particular on contemporary arguments from design. For reasons that will soon be clear, however, it is unlikely that Ruse would offer the same reinterpretation.

Ruse looks to history for help in answering his questions, and that is where I will begin as well. According to Ruse, the classic argument from design has two stages. The first is an argument based on our observations of nature for the conclusion that adaptive complexity is exhibited, not just by human contrivances, but also by other parts of nature or even by the natural world taken as a whole. The second is an argument from natural adaptive complexity to one or more intelligent designers of that complexity. Plato defends both stages of this argument, ultimately arguing for a “Demiurge” who, guided by the world of Forms, imposes order on a pre-existing world of becoming.1 Aristotle accepts the first stage of the argument, but not the second. He believes that teleological order has always existed; thus, he feels no need to reduce final causes to intentions that make reference to the future but exist prior to their effects.2 Ancient atomists represent a third option, denying that adaptive complexity is eternal, but rejecting intelligent design in favor of pure chance.3

Now let’s fast forward a couple millennia to David Hume’s Dialogues Concerning Natural Religion.4 The character Cleanthes believes that complex mechanical order can be observed throughout nature. The world as a whole, he says, is a “machine,” which is divided into smaller machines, which in turn are made up of even smaller machines, and so on. Philo challenges Cleanthes’ claim that the world as a whole is machine-like, but in Part XII he admits that various organic systems are genuine examples of adaptive complexity. Instead of concluding, however, as Cleanthes does, that these organic systems were intelligently designed, Philo draws a more cautious conclusion, namely, that the causes of mechanical order within nature probably bear some analogy to the causes of machines.

Given this more modest conclusion, do we still want to call Philo’s argument an argument from design? If we do, then we must, I believe, add something to what Ruse says about the significance of Darwin’s theory for the argument from design. Darwin’s theory of natural selection may refute the classic argument from design, as Ruse says; but it also vindicates Philo’s argument from design, or at least its conclusion, since organic systems and machines are both produced by a process of imperfect replication and selection. In the case of machines, the process is one of trial and error, a combination of replication with non-random variation and conscious selection. For example, human designers are not capable of building a complex machine like a Sopwith Camel from scratch. Rather, they start with the plane built by the Wright brothers, then replicate that plane with variations they think might improve performance, preserving what works in future generations and discarding what doesn’t. Thus, one way that the causes of mechanical order in the living world could bear an analogy to the causes of machines and yet not involve conscious intentions is by involving replication with random variation and non-conscious selection. Such a process will be much slower than the process by which the airplane has evolved, but it will be analogous. Therefore, Darwin’s theory showed that the causes of organic systems really are analogous to the causes of machines, just as Philo, and probably Hume as well, had concluded.

Of course, just because Philo’s conclusion is true doesn’t mean that his argument is a good one. Ruse, however, holds two related views that support the position that Philo’s inference is correct. First, he believes that the way the parts of organic systems are ordered is strikingly similar to the way that the parts of machines are ordered and plainly dissimilar to the way matter is ordinarily arranged in nature. Second, he holds, no doubt partly on the basis of the first view, that this sort of order, this adaptive complexity, demands a very special sort of explanation. These two views support the position that Philo’s argument is a good one, that living things and machines really are relevantly similar, and that it follows from this similarity that their causes probably resemble each other in some substantial way.

It is somewhat risky, however, for a naturalist to accept this position. To see why, more history is needed. As Ruse notes, it was widely believed by Darwin’s time that adaptive complexity is limited to the living world and human contrivances. It was also widely believed that cells are relatively simple things. The cell theory had been formulated in the 1830s, and some biologists believed that the cell wall and nucleus were functionally important. But others, like T. H. Huxley, believed that the half liquid contents of the cell are the “physical basis of life.”5According to this “protoplasmic theory of life,” the first life forms or proto-life forms on earth were just lumps of protoplasm that, despite their homogeneity, were nevertheless capable of nutrition and reproduction.6If life could be as simple as this, then by providing an account of how complex life could evolve from simple life, Darwin appeared to have explained all of the adaptive complexity in the natural world.

Advances in science since Darwin, however, have disturbed this tidy picture. Many philosophers and scientists now claim to find adaptive complexity in two parts of nature that at least appear to fall outside of the reach of Darwin’s theory in its contemporary form. First, biologists and biochemists tell us that an individual living cell is itself a highly structured system, one that displays complex mechanical order just as much as larger biological systems. This raises the question of how the first life on earth (which I will call “primitive life”) came into existence. Part of the problem is that natural selection seems to depend on the existence of a genetic system composed of nucleic acids and capable of self-replication, but any such system already displays adaptive complexity. Origin-of-life researchers have many theories, but all of these theories face serious obstacles, and nothing like a consensus has emerged. In fact, researchers don’t even agree on such basic issues as whether a genetic system or a metabolic cycle was the first step on the way to life. Second, physicists tell us that certain physical parameters of the universe are fine-tuned for the existence of life. To say that a physical parameter like the gravitational constant or the mass of the proton or the rate of expansion of the big bang is “fine-tuned for life” is to say that the range of values of that parameter that are life-permitting (i.e. that do not entail the physical impossibility of life assuming no changes to other parameters) is very small compared to the range of all theoretically possible values of that parameter. Many physicists seem to regard this fine-tuning as an instance of adaptive complexity, or at least as something that, like adaptive complexity, needs a special explanation; but there is no agreement on what that explanation is.

Assume that primitive life and cosmic fine-tuning really are examples of adaptive complexity. Then the position that Philo’s argument is a good one threatens to have consequences which metaphysical naturalists will find unpalatable. For that position implies that the causes of all instances of adaptive complexity, including newly discovered ones, are probably analogous to the causes of machines; and just because it was possible at the time of Darwin to accept this analogy without positing supernatural intelligence does not guarantee that this is possible today. I doubt Ruse would be sympathetic to such radical suggestions. More than twenty years ago he claimed that science by definition deals only with the natural, which implies that no explanation that makes reference to the supernatural is scientific.7In Darwin and Design, he praises Aristotle for recognizing that “a designing mind as such can have no place in science.”8But even if Ruse’s claim about the definition of “science” is correct, it does not follow that methodological naturalism is true–-that we should never appeal to the supernatural in our attempts to explain the natural. For the issue here is not a verbal one–-the issue is not how the word “science” is properly used.9 Rather, the issue is whether or not people who investigate the causes of natural events should look only for naturalistic causes or also for supernaturalistic ones. Whether one interprets this issue as the question of whether scientists should broaden their scientific investigations or as the question of whether scientists should broaden their investigations beyond the boundaries of science will depend, of course, on the definition of “science.” But the definition won’t settle the issue. My own view is that a weak form of methodological naturalism is justified by the success in both science and everyday life of finding good naturalistic explanations of natural phenomena. Such success supports the view, which I call “modest methodological naturalism,” that, prior to investigation, a natural phenomenon is very likely to have a natural cause and hence appeals to the supernatural are justified only as a last resort. (By “supernatural” entities, I mean entities that are neither ontologically nor causally reducible to the entities studied by physical scientists and yet can causally influence such entities.) Let’s assume the truth of my modest methodological naturalism and examine the cases of primitive life and cosmic fine-tuning in the light of Philo’s argument.

Just as Plato and Aristotle reject the ancient atomists’ attempt to explain adaptive complexity by appealing to the random clumping of atoms, so too almost all origin of life researchers reject the view, held by such prominent scientists as Jacques Monod and even Richard Dawkins, that the order in the first living thing can plausibly be attributed to a highly improbable chance event, a single random collision of molecules.10Such an event is simply too improbable to take seriously, which is to say that, once again, adaptive complexity calls for a special sort of explanation. Should, then, we agree with Philo that the causes of primitive life are probably analogous to the causes of machines? I’m inclined to say “yes.” But notice that this does not mean we must agree with Cleanthes that supernatural intelligence is involved. Whether one accepts an “RNA world” scenario or a metabolism first view, non-genetic natural selection may play a crucial role in one’s theory. Granted, advocates of the RNA first view sometimes defend that view by claiming that RNA had to appear first so that natural selection can begin to operate; but it seems likely that they must ultimately postulate a previously existing biochemical world in which non-genetic natural selection leads to RNA. How does non-genetic natural selection work in this case? We don’t know yet, but if we agree with Philo’s argument and also maintain modest methodological naturalism, then even in the absence of any consensus on the details we should conclude that natural selection is the most likely explanation of adaptive complexity in primitive life.

What about cosmic fine tuning? Here the claim that adaptive complexity is present is much more controversial than in the case of primitive life. One difference is that we can observe other physical objects besides machines and living things and in this way learn that the order machines and living things exhibit is very unusual and so in need of special explanation. But even if there are other universes, we cannot observe them, making it difficult to justify the claim that the values of the physical parameters of our universe are “unusual.” On the other hand, many of the values of these parameters involve asymmetries or seem in some other way to be “unnatural” or less “simple” and hence intrinsically less probable than other theoretically possible values. This is, I believe, part of the reason that so many physicists and philosophers find an appeal to brute fact in the cosmic case so unsatisfying.

What sort of explanations of cosmic fine tuning have been offered? Some philosophers and scientists have appealed to supernatural intelligence. Notice that such an appeal in the cosmic case is not as blatant a violation of modest methodological naturalism as in the origin-of-life case. For the most general features of the universe, especially ones that may not follow from physical law, are just the sort of features that are most plausibly accounted for by a non-intervening creator’s activity. Others have tried to explain cosmic fine-tuning by appealing to multiple universes. Interestingly, many of these appeals parallel the ancient atomists’ attempt to explain biological order. The claim is that vastly many, or even infinitely many, universes exist, or have existed in succession, and that the values of the relevant physical parameters vary randomly from one universe to another. Thus, it is not surprising that one or more universes would have the values needed for life, and it is not surprising that the universe we observe is one of the life-permitting ones, because we could not exist in any of the others. This sounds an awful lot like: there are vastly or infinitely many atoms that randomly form different arrangements with each other. Thus, given enough time, it is inevitable that our world would exhibit adaptive complexity, and it is not surprising that we happen to observe the world when it is so ordered because our existence depends on that order. If we find the atomists’ explanation inadequate, then perhaps we should also reject the common multiple universes explanation.

Is there some other option besides an appeal to supernatural intelligence or chance? Or does agreement with Philo’s argument from design (combined with the assumption that cosmic fine- tuning really is an example of adaptive complexity) commit us to concluding that the universe was intelligently designed? One interesting option that is not popular among physicists, but which anyone who defends both Philo’s argument from design and methodological naturalism should find at least initially attractive, is a multi-universe theory independently suggested by the philosopher Quentin Smith and the physicist Lee Smolin.11 Smith and Smolin suggest that a universe is produced when the black hole of a parent universe collapses. If its physical parameters are near their “natural” values, then the universe will not inflate or will inflate without producing black holes and so will have no offspring. If, on the other hand, a universe’s physical parameters are more like the values in our universe, then it will have offspring. These offspring will tend to resemble their parent, although mutations are possible because, when a black hole collapses, fluctuations resulting from the state of high entropy inside the hole can scramble the physical parameters of the parent universe that would otherwise be passed on to its offspring.

According to this theory, it is natural selection that accounts for cosmic fine-tuning. The physical parameters of a universe are its cosmic genes, which are replicated, often imperfectly, in the next generation of universes. Because the values that result in more black holes and hence more offspring are the “unnatural” ones that are also necessary for life, universes with unnatural physical parameters are ultimately selected and eventually predominate, making the existence of life- permitting universes much less surprising. Of course, life is, in a sense, epiphenomenal on this theory – the universe is really fine-tuned for black hole production–-but this is just a cosmic version of Darwin’s “principle of “correlated variation.”12If Smith and Smolin’s theory turns out to be true, then Philo’s argument will be vindicated once again, and once again such vindication will not require believing in supernatural intelligence.

My aim in this paper has been to extend and, in the case of Hume, modify Ruse’s history of the argument from design in an effort to shed light on contemporary design arguments. My conclusion is that Ruse is right when he says that the past, even if it doesn’t answer all of our present questions about teleological thinking, does suggest interesting directions for answering them. As I mentioned earlier, however, I doubt Ruse would be willing to travel in the same directions I do. His adherence to strict methodological naturalism blocks his way. Because I accept only a modest methodological naturalism, I take the possibility of a successful argument from design very seriously. This means that theories like Darwin’s and perhaps even Smith and Smolin’s have a starring instead of a merely supporting role to play in the justification of a naturalistic worldview.


Works Cited

Darwin, Charles. The Origin of Species. New York: The New American Library. 1958.

Fry, Iris. The Emergence ofLife on Earth: A Historical and Scientific Overview. New Brunswick, New Jersey: Rutgers UP. 2000.

Hume, David. Dialogues Concerning Natural Religion. Ed. Martin Bell. New York: Penguin Books, 1990. Plantinga, Alvin. Methodological naturalism? Perspectives on Science and Christian Faith 49 (Sept. 1997): 143-154.

Ruse, Michael. Darwinism Defended: A Guide to the Evolution Controversies. Reading, Massachusetts: Addison-Wesley. 1982.

Ruse, Michael. Darwin and Design: Does Evolution Have a Purpose? Cambridge, Massachusetts: Harvard UP. 2003.

Smith, Quentin. A Natural Explanation of the Existence and Laws of Our Universe. Australasian Journal of Philosophy 68.1 (March 1990): 22-43.

Smolin, Lee. The Life ofthe Cosmos. Oxford: Oxford UP. 1997.


  1. Michael Ruse, Darwin and Design: Does Evolution Have a Purpose? (Cambridge, Massachusetts: Harvard UP, 2003): 12-17.
  2. Ruse, 17-19.
  3. Ruse, 11-12.
  4. David Hume, Dialogues Concerning Natural Religion, ed. Martin Bell (New York: Penguin Books, 1990).
  5. Iris Fry, The Emergence of Life on Earth: A Historical and Scientific Overview (New Brunswick, New Jersey: Rutgers UP, 2000): 57.
  6. Fry, 57-59.
  7. Ruse, 322.
  8. Ruse, 19.
  9. Alvin Plantinga, Methodological naturalism?, Perspectives on Science and Christian Faith 49 (1997): 146.
  10. Fry, 193-197.
  11. Quentin Smith, “A Natural Explanation of the Existence and Laws of Our Universe,” Australasian Journal of Philosophy 68.1 (March 1990) 22-43; and Lee Smolin, The Life of the Cosmos (Oxford: Oxford UP, 1997).
  12. Charles Darwin, The Origin of Species (New York: The New American Library, 1958): 34-35.

Paul Draper

Paul Draper is Professor of Philosophy and Director of the Master of Arts in Liberal Studies program at Florida International University. His primary research interests are in philosophy of religion and philosophy of science. His most recent publication is "Cosmic Fine-Tuning and Terrestrial Suffering: Parallel Problems for Naturalism and Theism," forthcoming in the October 2004 issue of American Philosophical Quarterly.