Evolution and Creationism From Core Questions in Philosophy: A Text With Readings (fourth Edition)

By Elliot Sober

Prentice Hall 2005

In this lecture, I want to describe some of the main lines of evidence that lead biologists to think the hypothesis of evolution is correct. Whereas Aquinas, Paley, and others held that the intricacy and adaptedness of organisms can be explained only by viewing them as the product of intelligent design, the modem theory of evolution, stemming from Charles Darwin's (1809-1882) ideas, holds otherwise. Because this is an introductory text, I won't be able to describe all the interlocking arguments biologists now offer for evolutionary theory. Nor will I be able to give all the details on even the ones I do touch on. I also won't take much time to address all the criticisms of evolutionary theory that creationists have advanced.


Creationists (sometimes calling themselves "scientific creationists" or "intelligent de- sign theorists") are present-day defenders of the design argument. Although they agree among themselves that intelligent design is needed to explain some features of the living world, they disagree with each other about various points of detail. Some hold that the earth is young (around 10,000 years old), whereas others concede that it is ancient-about 4.5 billion years old, according to current geology. Some creationists maintain that each species was separately created by an intelligent designer, whereas others concede that biologists are right when they assert, as Darwin did, that all life on earth traces back to a common ancestor. further point of disagreement concerns which characteristics of organisms demand explanation by intelligent design. Some hold that every complex adaptation--the wings of birds, the temperature regulation system found in mammals, the eye--requires explanation in terms of intelligent design. Others disagree with modern science much less; they assert that only one or two features of life forms demand intelligent design explanations. These creationists agree with current biology, except when they consider the origin of life or the emergence of consciousness.

To further clarify what creationism involves, let's consider three possible relationships that might obtain among God (&), mindless evolutionary processes (E), and the observed features of organisms (0):


Theistic evolutionism says that God set mindless evolutionary processes in motion; these processes, once underway, suffice to explain the observed features of organisms. Atheistic evolutionism denies that there is a God, but otherwise agrees with theistic evolutionism that mindless evolutionary processes are responsible for what we see in organisms. Creationism, as I understand it, disagrees with both theistic evolutionism and atheistic evolutionism. Creationism maintains not just that God set mindless evolutionary processes in motion, but that he also periodically intervenes in these mindless processes, doing work that mindless natural processes are inherently incapable of doing.

You can see from these three options that belief in evolutionary theory is not the same as atheism. In my opinion, current evolutionary theory is neutral on the question of whether there is a God. Evolutionary theory can be supplemented with a claim, either pro or con, concerning whether God exists. Evolutionary theory, however, is not consistent with creationism. Evolutionary theory, as I understand it, holds that mindless evolutionary processes suffice to explain the features of living things. Creationism denies this. 


Some of the most frequently repeated creationist arguments contain mistakes and confusions. For example, creationists have argued that evolutionary theory is on shaky ground because hypotheses about the distant past can't be proven with absolute certainty. They are right that evolutionary theory isn't absolutely certain, but then nothing in science is absolutely certain. What one legitimately strives for in science is powerful evidence showing that one explanation is far more plausible than its competitors. Biologists now regard the hypotheses of evolution as about as certain as any hypothesis about the prehistoric past could be. Naturally, no scientist was on the scene some 3.8 billion years ago when life started to exist on Earth. It is nonetheless possible, however, to have strong evidence about matters that one can't directly observe, as I hope my previous discussion of abduction has made clear. Another example of an error creationists make is their discussion of the Second Law of Thermodynamics. They claim this law makes it impossible for order to arise from disorder by natural processes. Natural processes can lead an automobile to disintegrate into a junk heap, but creationists think the law says that no natural process can cause a pile of junk to assemble itself into a functioning car. Here creationists are arguing that a physical law is inconsistent with the claim that life evolved from nonlife. What the Second Law actually says is that a closed system will (with high probability) move from states of greater order to states of lesser order. But if the system isn't closed, the law says nothing about what will happen. So if the Earth were a closed sys- tem, its overall level of disorder would have to increase. But, of course, the Earth is no such thing-energy from the sun is a constant input.

If we think of the universe as a whole as a closed system, then thermodynamics does tell us that disorder will increase overall. But this overall trend doesn't prohibit "pockets" of order from arising and being maintained. The Second Law of Thermodynamics offers no basis whatever for thinking that life couldn't have evolved from nonlife.

A full treatment of the evolution versus creationism debate would require me to describe the positive explanations that creationists have advanced. If you want to com- pare evolutionary theory and creationism, you can't just focus on whatever difficulties there may be in evolutionary ideas. You've also got to look carefully at what the alternative is. Doing this produces lots of difficulties for creationism. The reason is that creationists have either been woefully silent on the details of the explanation they want to defend, or they have produced detailed stories that can't withstand scientific scrutiny. For example, "young earth creationists," as I mentioned, maintain that the earth is only a few thousand years old. This claim conflicts with a variety of very solid scientific findings, from geology and physics. It isn't just evolutionary theory that you have to reject if you buy into this version of creationism, but a good deal of the rest of science as well.

As I also indicated above, there are many different versions of creationism. Creationism is not a single theory, but a cluster of similar theories. In the present lecture, I won't attempt to cover all these versions, but will focus mainly on one of them. The one I'm going to start off with isn't Paley's, but it is worth considering nonetheless. According to the version of creationism I want to examine, God designed each organism to be perfectly adapted to its environment. In this lecture, I'll explain what Darwin's theory says and why I think it is vastly superior to this version of creationism. However, we can't conclude from this that Darwinism is superior to all forms of creationism. In fact, I'll conclude the lecture by describing a second version of creationism that is immune to the criticisms that undermine the "perfectionist" version. And I'll return, at the end, to the version of creationism that Paley actually defends.


In 1859 Darwin put forward his theory of evolution in his book The Origin of Species. Many of his ideas are still regarded as correct. Some have been refined or expanded. Others have been junked entirely. Although evolutionary theory has developed a long way since Darwin's time, I'll take his basic ideas as a point of departure.

Darwin's theory contains two main elements. First, there is the idea that all present- day life is related. The organisms we see didn't come into existence independently by separate creation. Rather, organisms are related to each other by a family tree. You and I are related. If we go back far enough in time, we'll find a human being who is an ancestor of both of us. The same is true of you and a chimp, though, of course, one must go back even further in time to reach a common ancestor. And so it is for any two present-day organisms. Life evolved from nonlife, and then descent with modification gave rise to the diversity we now observe.

Notice that this first hypothesis of Darwin's says nothing about why new characteristics arose in the course of evolution. If all life is related, we may ask why it is that we find the variety of organisms we do. Why aren't all living things identical? The second part of Darwin's theory is the idea of natural selection. This hypothesis tries to explain why new characteristics appear and become common and why some old characteristics disappear.

It is very important to keep these two elements in Darwin's theory separate. The idea that all present-day living things are related isn't at all controversial. The idea that natural selection is the principal cause of evolutionary change is somewhat controversial, although it is still by far the majority view among biologists.

Part of the reason it is important to keep these ideas separate is that some creationists have tried to score points by confusing them. Creationists sometimes suggest that the whole idea of evolution is something even biologists regard with great doubt and suspicion. But the idea that all life is related isn't at all controversial. What is controversial, at least to some degree, are ideas about natural selection. I'll begin by describing the basic idea of natural selection. Then I'll say a little about what is still somewhat controversial about the idea. I'll then turn to the quite separate idea that all life is related and describe some of the lines of evidence that" make biologists regard this idea as overwhelmingly plausible.


Here's a simple example of how natural selection works. Imagine a population of zebras that all have the same top speed. They can't run faster than 38 mph. Now imagine that a novelty appears in the population. A mutation occurs-a change in the genes found in some zebra-that allows that newfangled zebra to run faster-at 42 mph, say. Suppose running faster is advantageous, because a fast zebra is less likely to be caught and eaten by a predator than a slow one is. Running fast enhances the organism's fitness--its ability to survive and reproduce. If running speed is passed on from parent to offspring, what will happen? What will occur (probably) is that the fast zebra will have more offspring than the average slow zebra. As a result, the percentage of fast zebras increases. In the next generation, fast zebras enjoy the same advantage, and so the characteristic of being fast will again increase in frequency. After a number of generations, we expect all the zebras to have this new characteristic. Initially, all the zebras ran at 38 mph. After the selection process runs its course, all run at 42 mph. So the process comes in two stages. First, a novel mutation occurs, creating the variation upon which natural selection operates. Then, natural selection goes to work changing the composition of the population:


100% run at 38 mph A novel mutant runs at 42 mph; at 38 mph 100%  run at 42 mph

We may summarize how this process works by saying that natural selection occurs in a population of organisms when there is inherited variation in fitness. Let's analyze what this means. The organisms must vary; if all the organisms are the same, then there will be no variants to select among. What is more, the variations must be passed down from parents to offspring. This is the requirement of inheritance. Lastly, it must be true that the varying characteristics in a population affect an organisms's fitness--its chance of surviving and reproducing. If these three conditions are met, the population will evolve. By this, I mean that the frequency of characteristics will change.

The idea of natural selection is really quite simple. What Darwin did was to show how this simple idea has many implications and applications. Merely stating this simple idea wouldn't have convinced anyone that natural selection is the right explanation of life's diversity. The power of the idea comes from the numerous detailed applications. Notice that the introduction of novel characteristics into a population is a pre- condition for natural selection to occur. Darwin didn't have a very accurate picture of how novel traits arise. He theorized about this, but didn't come up with anything of lasting importance. Rather, it was later in the nineteenth century that Mendel started to fill in this detail. Genetic mutations, we now understand, are the source of the variation on which natural selection depends.Notice that the little story I've told describes a rather modest change that occurs within a species of zebras. A single species of zebras goes from one running speed to another. Yet, Darwin's 1859 book was called The Origin of Species. How does change within a species help explain the coming into existence of new species-of speciation?s


Darwin's hypothesis was that small changes in a population (like the one I just described) add up. Given enough little changes, the organisms will become very different. Modern evolutionists usually tell a story like the following one. Think of a single population of zebras. Imagine a small number of zebras are separated from the rest of the population for some reason; maybe they wander off or a river changes course and splits the old population in two. If the resulting populations live in different environments, selection will lead them to become increasingly different. Characteristics that are advantageous in one population will not be advantageous in the other. After a long time, the populations will have diverged. They will have become so different from each other that individuals from the one can't breed with individuals from the other. Because of this, they will be two species, not two populations belonging to the same species. Pretty much everybody in Darwin's day, including those who thought that God created each species separately, would have agreed that the little story about zebras evolving a greater speed could be true. The real resistance to Darwin's theory focused on his thesis that the mechanism responsible for small-scale changes within species also gives rise to large-scale changes, namely, to the origin of new species. This was a daring hypothesis, one that is now the mainstream view in evolutionary theory, though it is still somewhat controversial. In saying that it is still somewhat controversial, I mean that there are evolutionists today who doubt that natural selection had the importance Darwin thought it did. They hold that other mechanisms play an important role in evolution. They grant that natural selection is part of the story, but deny it is the whole story. Deciding how important natural selection has been is a subject of continuing investigation in evolutionary theory. Another kind of open question exists about natural selection. Even biologists who hold that natural selection is the major cause of evolution are sometimes puzzled about how it applies in particular cases. For example, it is still rather unclear why sexual reproduction evolved. Some creatures reproduce sexually, others asexually. Why is this? Even biologists who expect that the answer will be in terms of natural selection are puzzled. So there are two sorts of open questions pertaining to natural selection. First, there is the issue of how important natural selection has been in the evolution of life. Second, there is the question of how the idea of natural selection should be applied to account for this or that characteristic. What I want to emphasize about both these questions is that they aren't questions about whether we are related to chimps. This isn't controversial. The questions I've mentioned so far have to do with the mechanism that accounts for why life evolved as it did, not whether it evolved.


I turn now to this uncontroversial idea. Why do biologists think it is so clear that living things are related to each other-that there is a family tree of terrestrial life just like there is a family tree of your family? Two kinds of evidence have seemed persuasive. I won't give the details here; rather, I want to describe the kinds of arguments biologists deploy. As a philosopher, I'm more interested that you grasp the logic of the arguments; for the biological details, you'll have to consult a biology book. To illustrate how one line of argument works, consider this simple problem. Sup- pose I assign a philosophy class the job of writing an essay on the meaning of life. As I read through the papers, I notice that two students have handed in papers that are word-for-word identical. How should I explain this striking similarity? One possibility, of course, is that the students worked independently and by coincidence arrived at exactly the same result. The independent origin of the two papers isn't impossible. But I would regard this hypothesis as extremely implausible. Far more convincing is the idea that one student copied from the other or that each of them copied from a common source--a paper downloaded from the Internet, perhaps. This hypothesis is a more plausible explanation of the observed similarity of the two papers.


The plagiarism example illustrates an idea that the philosopher Hans Reichenbach (in The Direction of Time, University of California Press, 1956) called the Principle of the Common Cause. Let's analyze the example more carefully to understand the rationale of the principle. Why, in the case just described, is it more plausible that the students copied from a common source than that they wrote their papers independently? Consider how probable the matching of the two papers is, according to each of the two hypotheses. If the two students copied from a common source, then it is rather probable that the papers should closely resemble each other. If, however, the students worked in- dependently, then it is enormously improbable that the two papers should be so similar. Here we have an application of the Surprise Principle: If one hypothesis says that the observations are very probable whereas the other hypothesis says that the observations are very improbable, then the observations strongly favor the first hypothesis over the second. The Principle of the Common Cause makes sense because it is a consequence of the Surprise Principle. The example just described involves hypotheses that describe mental activity--when students plagiarize they use their minds, and the same is true when they write papers independently. However, it is important to see that the Principle of the Common Cause also makes excellent sense when the hypotheses considered do not describe mental processes.  I have a barometer at my house. I notice that when it says "high," there usually is a storm the next day; and when it says "low," there usually is no storm the next day. The barometer reading on one day and the weather on the next are correlated. It may be that this correlation is just a coincidence; perhaps the two events are entirely in- dependent. However, a far more plausible hypothesis is that the reading on one day and the weather on the next trace back to a common cause--namely, the weather at the time the reading is taken: The common cause hypothesis is more plausible because it leads you to expect the correlation of the two observed effects. The separate cause hypothesis is less plausible because it says that the observed correlation is a very improbable coincidence. Notice that the hypotheses here considered do not describe the mental activities of agents.


I'll now apply this principle to the evolutionary case. One reason biologists think all life is related is that all organisms (with some minor exceptions) use the same genetic code. To understand what this means, think of the genes in your body as a set of instructions for constructing more complex biological items-amino acids and then proteins, for example. The total sequence of genes in your body and the sequence in a frog's are different. The striking fact, however, is that the gene that codes for a given amino acid in a frog codes for that very same amino acid in people. As far as we now know, there is no reason why the genes that code for a given amino acid had to code for that acid rather than some other. The code is arbitrary; there is no

functional reason why it has to be the way it is. [Don't be misled by my talk of codes here. This word may suggest intelligent design, but this isn't what biologists mean. Genes cause amino acids to form; for present purposes, this is a perfectly satisfactory way to understand what it means for genes to "code for" this or that amino acid.]  

How are we to explain this intricate similarity among the genetic codes that different species use? If the species arose independently of each other, we would expect them to use different genetic codes. But if those species all trace back to a common ancestor, it is to be expected that they will share the same genetic code. The Principle of the Common Cause underlies the belief that evolutionary biologists have that all living things on earth have common ancestors.


There is a second feature of life that lends plausibility to the hypothesis that different species have common ancestors. It is the fact that organisms are not perfectly adapted to their environments. When I described Paley's design argument in Lecture 5, I tried to convey the idea that Paley was very impressed by the perfection of nature. Paley thought this exquisite fittingness of organisms to the environments they inhabit can be explained only by the hypothesis of intelligent design. Since Darwin's time, however, biologists have looked more closely at this idea. What biology tells us is that organisms are not perfectly suited to their environments. They are suited in a passable, often makeshift, way. Adaptation is often imperfect; it is good enough so that species avoid extinction, at least in the short run.

Consider first an example that the biologist Stephen Jay Gould discusses in his book The Panda's Thumb (W. W. Norton, 1980). Pandas are vegetarians; bamboo shoots are pretty much the only thing they eat. A panda strips bamboo by running the branch between its paw and what seems to be a thumb. On closer examination, how- ever, it is clear that this thumb isn't an opposable digit. Rather, the thumb is a spur of bone that sticks out from the panda's wrist.

This device for preparing bamboo is really quite clumsy. It would be no great challenge for a skillful engineer to design a better thumb for the panda to use. If God had made organisms perfectly adapted to their ways of life, it really would be quite puzzling why the panda is so ill-equipped. The hypothesis that pandas are closely related to carnivorous bears, however, allows us to understand why pandas have such an odd appliance attached to their wrists. There is a remarkable similarity between the paw structure of pandas and that of their nearest relatives. The panda's thumb is a modification of a structure that its ancestors possessed.

In short, the panda's thumb is puzzling if you subscribe to the hypothesis that God made each organism perfectly adapted to its environment. On the other hand, the hypothesis that pandas are descended from carnivorous bears makes it unsurprising that they have thumbs of the sort they do. The Surprise Principle says that the latter hypothesis is the more plausible one.

A creationist might concede that the panda's thumb is not an adaptation that exists to help individual pandas, but then suggest that the trait exists for the sake of maintaining the balance of nature. If pandas were more efficient at stripping bamboo, perhaps bamboo plants would go extinct and this would disrupt the stability of the whole ecosystem. Here the creationist is making a new suggestion, one that needs to be evaluated on its own terms. The suggestion is that an intelligent designer constructed ecosystems so that they would be stable.

To see how this idea runs into problems, we must shift to a new type of example. Biologists estimate that over 99% of the species that have ever existed are now extinct. Ecosystems are not terribly stable, in that there have been periodic mass extinctions that have wiped out wide swaths of the living world. Just as we find that individual organisms are not perfectly suited to the tasks of surviving and reproducing, we also find that ecosystems are far from perfectly suited to the tasks of remaining stable and persisting through time. 

There is another pattern of argument that biologists use, one that resembles what they say about the panda's thumb. Biologists claim that vestigial organs are evidence that various species have a common ancestor. You may recall from high school biology that human embryos develop gill slits and then lose them. These gill slits, as far as scientists know, have no function; if each species were separately designed by a superintelligent designer who wanted organisms to be perfectly adapted, it would be very surprising to find gill slits in humans. However, if human beings are descended from ancestors who had gills as adults, the characteristic found in human embryos would be easier to understand. Natural selection modified the ancestral condition; human beings have gills only in the embryo stage, rather than in both the embryo and in the adult. A similar line of argument is used to explain why chi<:ken embryos have teeth, which are reabsorbed into the gum before the chick is born. 

I've mentioned two lines of evidence that lead biologists to think that all life is related. There is the fact of arbitrary similarity and the fact of imperfect adaptation. Both are evidence favoring the hypothesis that life evolved--that organisms alive today are descended from common ancestors and diverged from each other by the process of natural selection. These two types of evidence count against the idea that organisms originated independently as the result of a superintelligent designer's making each of them perfectly adapted.


I've emphasized the importance of imperfect adaptation as evidence for the hypothesis of common ancestry. More nearly perfect adaptation provides evidence that is much less telling. For example, consider the fact that sharks and whales both have a streamlined body shape. Is this strong evidence that they have a common ancestor? I would say not. There is an obvious functional reason why creatures that spend their lives swimming through water should be shaped like this. If there is life in other galaxies and if some of that life is about as big as a whale or shark and also lives in water, we would probably expect it to have this sort of shape. Even if terrestrial life and life on other galaxies aren't descended from common


Humans from Nonhumans, Life from Nonlife

When people hear about the idea of evolution, there are two parts of the theory that sometimes strike them as puzzling. First, there is the idea that human beings are descended from Apelike ancestors. Second, there is the idea that life evolved from nonliving materials. 

Scientists believe the first of these statements because there are so many striking similarities between apes and human beings. This isn't to deny that there are differences. However, the similarities (of which a few examples are given in this lecture) would be expected if humans and apes have a common ancestor, but would be quite surprising if each species was separately created by a superintelligent designer. 

There is a big difference between having evidence humans are descended from apelike ancestors and having an explanation of precisely why this happened. The evidence for there being a common ancestor is pretty overwhelming; but the details of why evolution proceeded in just the way it did are less certain. Students of human evolution continue to investigate why our species evolved as it did. In contrast, the claim that we did evolve isn't a matter of scientific debate. 

What about the second idea-that life arose from nonlife? Why not maintain that God created the first living thing and then let evolution by natural selection produce the diversity we now observe? Notice that this is a very different idea from what creationists maintain. They hold that each species is the result of separate creation by God. They deny that present-day species are united by common descent from earlier life forms. 

One main sort of evidence for thinking that life evolved from nonlife on Earth about four billion years ago comes from laboratory experiments. Scientists have created laboratory conditions that resemble the ones they believe were present shortly after the Earth came into existence about four and one-half billion years ago. They find that the nonliving ingredients present then can enter into chemical reactions, the products of which are simple organic materials.

For example, it is possible to run electricity (lightning) through a "soup" of inorganic molecules and produce amino acids. Why is this significant? Amino acids are an essential stage in the process whereby genes construct an organism. Similar experiments have generated a variety of promising results. 

This subject in biology--prebiotic evolution--is very much open and incomplete. No one has yet been able to get inorganic materials to produce DNA. But the promising successes to date suggest that further work will further illuminate how life arose from nonlife. 

Laboratory experiments don't aim to create a multicellular organism from inorganic materials. No one wants to make a chicken out of carbon, ammonia, and water. Evolution by natural selection proceeds by the accumulation of very small changes. So the transition from nonlife to life must involve the creation of a rather simple self-replicating molecule. Chickens came much later. 

A self-replicating molecule is a molecule that makes copies of itself. A molecule of this sort is able to reproduce; with accurate replication, the offspring of a molecule will resemble its parent. Once a simple self-replicating molecule is in place, evolution by natural selection can begin. 

It may sound strange to describe a simple self-replicating molecule as being "alive." Such a molecule will do few of the things that a chicken does. But from the biological point of view reproduction and heredity (that is, similarity between parents and offspring) are of the essence.



ancestors, there are some similarities we would expect to find nonetheless. I conclude that the streamlined shape of whales and sharks isn't strong evidence that they evolved from a common ancestor. The Surprise Principle explains why some similarities, but not others, are evidence for the hypothesis that there is a tree of life uniting all organisms on earth.


My argument so far has focused on comparing the following two hypotheses:

HI: Life evolved by the process of natural selection.

H2: A superintelligent designer separately created each species and made each of them perfectly adapted to their environment.

My view is that the available observations favor the first hypothesis over the second.

There are, however, other hypotheses besides H2 that might flesh out the idea that intelligent design is part of the explanation of some of the features that we observe in the living world. As mentioned earlier, creationism comes in many forms; H2 is just one of them. Consider, for example, the following hypothesis: H3: God created each species separately, but endowed them with the very characteristics they would have had if they had evolved by natural selection. H3 is a wild card; although the observations I've mentioned strongly favor HI over H2, they don't strongly favor HI over H2. Nothing I have, said shows that evolutionary theory is superior to the form of creationism just described.


Why is this? The reason is that H1 and H3 are predictively equivalent. If H1 predicts that life will have a particular feature, so does H3Although arbitrary similarities and imperfect adaptations disconfirm H2, they are perfectly consistent with H3. Does this mean the evolution hypothesis, H1, isn't very well supported? I would say not. Consider the following pair of hypotheses:

J1: You are now looking at a printed page.

J2: You are now looking at a salami.

You have excellent evidence that J1 is true and that J2 is false. J1 predicts that you are having particular sensory experiences; if J1 is true, you should be having certain visual, tactile, and gustatory sensations (please take a bite of this page). J2 makes quite different predictions about these matters. The sensory experiences you now are having strongly favor J1 over J2.

Now, however, let's introduce a wild card. What evidence do you have that J1as posed is true:

J3 There is no printed page in front of you, but someone is now systematically misleading you into thinking that there is a printed page in front of you. J1 and J3 are predictively equivalent. The experiences you now are having tell you that J1 is more plausible than J2, but they don't strongly favor J1 over J3.

In the section of this book that focuses on Descartes's Meditations the problem of choosing between J1 and J3 will be examined in detail. For now, what I want you to see is this: When you ask whether some hypothesis (HI or J1, for example) is strongly supported by the evidence, you must ask yourself what the alternatives are against which the hypothesis is to be compared. If you compare HI (or J1) with H2 (or J2), you'll conclude that H1 (or J1) is extremely well supported. However, the problem takes on a quite different character if you compare HI with Hs (or J1 with J3).


Where does Paley's version of the design hypothesis fit into our discussion of creationism? Well, Paley spends a lot of pages in his book Natural Theology celebrating what he thinks is the perfection of the adaptive contrivances found in nature. Paley describes what he takes to be nature's perfection in order to develop a more detailed picture of the characteristics that the intelligent designer possesses. For example, Paley thinks that organisms are by-and-large happy; he thinks this shows that God is benevolent. However, Paley's discussion of adaptive perfection comes after he presents his argument that an intelligent designer exists. Paley is very careful to separate his initial argument that God exists from his subsequent arguments that attempt to as- certain God's characteristics. And when we attend to Paley's argument for God's existence, we find that Paley says quite clearly that his argument does not depend on our observing that adaptations are perfect. Even if the watch we found on the beach kept time imperfectly, we'd still conclude that it was produced by intelligent design. Paley concludes, by the same reasoning, that the design hypothesis is overwhelmingly plausible even if we find that organisms are not perfectly adapted to their environments. 

We therefore have to conclude that H2 is not the best way to represent the version of creationism that Paley wanted to defend. The problem is not that H2 misrepresents what Paley believed. Rather, the problem is that Paley's argument for the existence of an intelligent designer considers a version of creationism that does not predict whether organisms will be perfectly or imperfectly adapted. Thus, the fact that H1 is better supported than H2 does not settle whether HI is better supported than the bare hypothesis that life has properties that are due to intelligent design. Let us call this stripped-down and minimalistic hypothesis H4.

The versions of creationism I have labeled H2 and H3 do make predictions about what we observe. This is why we were able to compare those predictions with the ones that are generated by evolutionary theory. However, what does H4 predict about the characteristics of living things? The problem is that H4 appears to be untestable. It cannot be said that evolutionary theory is better supported by the observations than H4 is; the reason is that it is impossible to evaluate what H4 tells us to expect when we look at organisms.


Creationism comes in many forms. Some of them make very definite predictions about what we observe. The version that says that God made organisms so that they I. are perfectly adapted to their environments makes predictions that do not accord  with what we observe. The version that says that God made organisms to look exactly as they would if they had evolved by the mindless process of natural selection makes the same predictions that evolutionary theory makes, and so our observations do not allow us to discriminate between evolutionary theory and this "mimicking" version of creationism. Finally, the bare, minimalistic version of creationism that says that God had some (unspecified) impact on the traits of living things is, I suggest, untestable. We have not found a version of creationism that makes definite predictions about what we observe and which is better supported by the observations than evolutionary theory is. Is there a version of creationism that has these two  characteristics?