Creationism vs. Evolution

When I was in the sixth grade, my parents took me to a nearby Unitarian church every Sunday. While they attended the "grownup" services (which seemed more like seminars on philosophy and cultures to me, but that's another article), I got to take part in various activities with the other kids my age. One Sunday the activity was a debate on creationism vs. evolution, with me taking the side of evolution and six girls, plus the grownup who was supervising us, taking the side of creationism. I don't remember any details of the discussion, but nobody changed anybody's mind.

The recent (November 2004) news that a school board in Pennsylvania voted to require "intelligent design" to be taught in biology classes made me think of that sixth-grade debate. Even if nobody changed anybody's mind, wasn't it still a good thing that the discussion could take place? In a church, which was where it took place, I would say yes, but there's a big difference between a church and a school science class, and that's what I started reflecting on when the news item brought up the memory. What if it had been in school that the debate had taken place? What, exactly, is the big difference?

Many creationist partisans, including Senator Rick Santorum of Pennsylvania, think there isn't any--at least, none that would make it improper to discuss creationism (when it is dressed up as "intelligent design" in an attempt to look like a scientific theory [0]) in a school science class. In 2002 he wrote an op-ed piece in the Washington Times which argued that the central issues are free speech (teachers have a right to teach "alternate theories of evolution" even if they are not considered true scientific theories by most scientists--Santorum quotes Voltaire to underline this aspect of the issue), majority opinion ("a recent poll...shows overwhelming support" for including "intelligent design" in the curriculum), and educational excellence ("many students will be denied a first-rate science education" if "intelligent design" isn't taught--he invokes language in the No Child Left Behind Act to further bolster this position). As far as I can tell, these are still claimed to be the central issues by creationist partisans today.

These arguments are interesting since they highlight the same issues that make critics of teaching "intelligent design" in science classes so concerned. Apparently we all want the same things--we just disagree on how best to get them. (Yes, that's meant to be sarcasm.) Perhaps this disagreement is simply due to the fact that honest people can come up with different answers to complex questions. But I think it might be useful to explore the possibility that the disagreement is due more to misconceptions about what evolution really says, what a scientific theory really is, and what a good science education really requires. So I'd like to conduct a brief "debate" here on the points raised above.

Isn't "intelligent design" a genuine alternative theory to evolution? Doesn't it seem like we're shortchanging our kids if we don't tell them about it in science classes?

No, "intelligent design" is not a genuine alternative theory to evolution. There are already many, many articles by reputable scientists explaining why (a good place to start is the Talk.Design site, particularly the FAQ articles), so I'll confine myself to a few major points here, since they seem to be brought up the most often.

First, the biggest piece of "evidence" for intelligent design is supposed to be the fact that the probability of a protein molecule, or a DNA or RNA molecule or any other molecule capable of supporting life as we know it, coming together by random chance on the primeval Earth is so small that it couldn't have happened that way. But that's a misunderstanding of what science says actually happened. The molecules that support life didn't come together by chance: they came together by a series of chemical reactions driven by the energy of the sun, and chemical reactions are highly nonrandom processes. Only certain reactions are allowed, and it's been shown that those reactions are quite capable of forming the building blocks of proteins and nucleic acids in a few weeks in the laboratory, so it seems highly likely that in a billion years on the primeval Earth the molecules of life could have formed. Similar arguments apply to the claim that, even if the first primeval DNA molecules could have arisen by chance, the complex structures of later organisms couldn't have (though this simple claim is often conflated with more complex, and vaguer, claims about complexity which I address in the next paragraph).

The next biggest piece of "evidence" for intelligent design is supposed to be the "irreducible complexity" of living organisms--which may be simply another way of stating the previous point, or it may be a new point in its own right (as I noted just now, it's hard to tell because the writers who make these arguments are often so vague that there's no way of knowing what they're really saying). Be that as it may, there is no such concept as "irreducible complexity" in science; work in chaos theory and nonlinear dynamics, and many computer simulations of such systems, show that complexity can be created where there was none before whenever a system is continuously exchanging energy with other systems, as the Earth is. There is no law of "conservation of complexity" in science. Also, the idea of "irreducible complexity" assumes that every part of every organism has a definite function that can never change (because the argument is that if any part of the structure were removed, that function couldn't be performed), which is known to be false--there are many, many examples of structures in organisms being "exapted" (the term was coined by Stephen Jay Gould) for new functions, and acquiring new structure in the process [1].

Finally, some people define "intelligent design" as the theory (which has been proposed by some scientists) that life on Earth did not actually start here; instead the Earth was "seeded" by microorganisms from space brought by intelligent aliens. However, the scientists who actually proposed this idea never claimed that the "seeding" was done by intelligent aliens--and even if it was, that poses no problem for the theory of evolution. It's perfectly possible that life did not originate on Earth, and if that were found to be the case, the theory of evolution could accommodate that new knowledge without a hitch. After all, you would still have to explain how the life that "seeded" Earth came into being--and the theory of evolution can do that. "Intelligent design" would either have to appeal to evolution to explain how the "intelligent designers" came to be, or reveal its true colors as a supernaturalist belief, not a scientific theory. Evolution is the only scientific theory we have that accounts for the diverse biosphere we observe on Earth (and which can account for any other such biological entities we might discover), and we would be shortchanging our kids if we told them otherwise.

But the majority of people support including "intelligent design" in the science curriculum. Shouldn't they have the right to decide what their kids are taught?

My initial response to this is to question whether it really is the majority that wants "intelligent design" taught, or just a vocal minority that wants to focus on just that one issue, whereas the majority of people have a spectrum of issues they're concerned about. But let's assume for the sake of argument that it is a majority. What then?

Well, scientific truth is not decided by majority vote. A poll taken in ancient times would have shown that the majority of people believed the Earth was flat. That was known by scientists to be a false belief even then--the ancient Greek geometers (who were perhaps not "scientists" in the modern sense but were certainly free inquirers in the same tradition) knew quite well that the Earth was round, by several valid lines of reasoning based on observations. Would it have been right to insist that Greek children be taught "flat Earth theory" in school because the majority favored it?

You may protest that that's not a fair question: after all, not all ancient Greeks were able to follow the arguments that showed the Earth was round (many had probably never even heard of them), so they were merely going with the prevailing beliefs of their time. But that's precisely why scientific truth is not decided by majority vote. Scientific truths are in principle accessible to anybody, but there is a catch: you have to be willing to take the time to understand them, and you have to be willing to play by the rules while you do so. Those rules were not made up by scientists for fun: they are the result of a long and painful process of learning how easy it is to fool yourself if you don't take proper precautions. Unless and until you take the time and follow the rules, your vote simply doesn't count; it's not that you're wrong, it's just that you don't yet have an opinion that's worth arguing about.

So when you ask what should be taught to kids in science classes, the answer is not "what the majority wants them to be taught", but "what the consensus of scientific opinion says should be taught". The consensus of scientific opinion is that evolution is true, and that "intelligent design" is not a scientific theory at all. Certainly there are many areas of controversy over the details of how evolution took place in specific cases (and those topics would be excellent ways to introduce students to controversial issues and how science deals with them), but the fact that evolution took place is not a matter of controversy, majority vote notwithstanding. If you allow the majority vote to overrule that scientific consensus, you're throwing away the very educational excellence that you said you wanted to preserve.

But shouldn't individual teachers have the right to express their own views? Doesn't that teach kids important lessons about free speech and tolerance for different opinions?

First of all, I have difficulty believing that any reputable science teacher would really be expressing their own views if they said that "intelligent design" was a genuine alternative scientific theory to evolution. I suspect that in the absence of severe pressure from school boards (who, after all, control teachers' livelihoods) and parents (whom teachers understandably don't want to offend, since their cooperation is vital in giving kids a good education), science teachers would never mention "intelligent design" at all in their classrooms. (And if a kid asks about it? The teacher would probably say that it wasn't a genuine scientific theory, and direct the student to the various resources available that explain why.) If I'm right and there are such teachers, and if free speech and the right to state one's own opinions, not opinions foisted on one by others, are so important, shouldn't these teachers be allowed to teach their own views? Isn't it a violation of their free speech rights to force them to teach something they don't agree with?

But let's put that argument aside, since presumably it would also be considered an unfair question, though it's a very good one. Let's assume for the sake of argument that the science teachers in the schools in question hold the opinion that "intelligent design" is a genuine scientific theory, despite the fact that the scientific consensus says otherwise. (By the way, in the Dover, PA case, the teachers actually refused to read the "statement" about intelligent design and evolution that the school board wanted read in biology classes--school administrators had to do it. So what we're about to say doesn't really apply to that case, but let's go on anyway.) Of course such teachers have a free speech right to express such opinions as their personal views, but that's not the same thing as teaching them as part of the science curriculum. The science curriculum should be decided by the current scientific consensus, as I argued above, and teachers who have personal opinions at variance with that should express them outside the context of teaching their class, and clearly labeled as their personal opinions and not accepted scientific theory. That's not a threat to freedom of thought: it's a perfectly justified insistence on intellectual honesty. And without intellectual honesty, you can't have real freedom of thought or educational excellence.

But what if the current scientific consensus is wrong? Isn't it a part of science to always consider that possibility, in the spirit of rational inquiry, and keep alternatives open, and allow dissenting views to be heard?

It's always possible that the current scientific consensus is wrong. However, in the case of evolution it's extremely unlikely. And even if it did turn out to be wrong in the case of evolution, "intelligent design" wouldn't be what replaced it.

Historians of science enjoy focusing on the revolutionary thinkers who (as they portray it) have shown the current scientific consensus to be wrong, such as Copernicus, Galileo, Newton, Lavoisier, Einstein. The glamor attached to such achievements is easily misconstrued, however, as evidence that it's easy for the current scientific consensus to be wrong, which naturally leads to the idea that "dissenting views" should be aired indiscriminately, since you can never be sure that the next Galileo or Einstein won't be among them.

In fact, since the advent of modern science, the current scientific consensus has almost never been wrong. It has continually been refined to broaden its scope of application and take account of new discoveries, but it has almost never been wrong [2]. Einstein's theory of relativity provides a perfect illustration of the misconception. It's often said that Einstein proved that Newton and pre-relativity physics were wrong. He didn't. All he showed was that Newton's laws of motion are limited in their scope of application. Within that scope they still work perfectly well. You don't have to use relativity to compute the trajectory of an artillery shell or a car skidding on ice. Does that mean that Einstein wasn't acting in a spirit of rational inquiry? Of course not. Einstein's discovery of special and general relativity is about as good an example of free and rational inquiry as you can find.

Don't let the fact that the current scientific consensus has almost never been wrong fool you into thinking that scientists don't consider alternatives, either. They do it all the time. Again relativity provides a good example: physicists have constructed a number of alternative theories of gravity, expressly for the purpose of having something to compare with relativity. All of those alternative theories have turned out to be wrong--that is, they have all been contradicted by experiments, while relativity has not. Good scientists are always keeping alternatives in mind, but they also understand when to throw alternatives out. And if one is considering possible alternatives to the theory of evolution, "intelligent design", since it isn't even a genuine scientific theory to begin with, is one that should be thrown out. Dissenting views don't get to be heard once they have been shown not to be tenable.

But let's tackle the deeper question head on: shouldn't biologists consider alternative theories to evolution, just as physicists have considered alternative theories to relativity? Well, it depends on what you mean by "alternative theories". All of the alternative theories of gravity that I mentioned above share many features with relativity, because they have to: there is so much data that has to be accounted for that a theory that wasn't very close to relativity to begin with wouldn't even be in the running. To a non-physicist all of those theories would look so much like relativity that the small differences would pale in comparison--a non-physicist would probably call them all "theories of relativity" and wouldn't much care about the fine points. In the same way, any "alternative theory" to evolution would have to account for so much data that it would end up being well nigh indistinguishable from evolution--the differences would be over fine points that a non-biologist would never consider sufficient to warrant a different name than "evolution". Needless to say, "intelligent design" is not such a theory.

Indeed, as I noted earlier, there are controversies within the theory of evolution; there are details on which there is not yet a full scientific consensus, and about which alternative theories are proposed. But those areas are all "fine points" that don't change the fundamental fact that the theory is a theory of evolution. For example, I said earlier that life was formed on Earth by chemical reactions driven by the energy of the Sun. You may have noticed that later on I mentioned an alternative (that life on Earth came via microorganisms from space--though I should note that this hypothesis was probably proposed partly tongue in cheek by Francis Crick and Leslie Orgel, who originated it). There's also another alternative, that the chemical reactions that started life on Earth were driven not by solar, but by geothermal energy (the theory is that early bacteria evolved in environments like hot springs or volcanic rock deep within the Earth, where there are species of bacteria found today living at temperatures up to 75 C). These are genuine alternative scientific theories of how evolution happened in a specific case, but they are all still theories of evolution [3]. There have been plenty of controversies about each of the three alternative theories of how life got started on Earth, but no controversy at all about the basic fact that it was evolution that did it. There are plenty of dissenting views in science, but there is also plenty of consensus about fundamental issues.

Discussing controversies and genuine alternative theories like these, and why they don't change the fundamental fact that evolution happened, would be a great way to teach students about biology in particular and science in general (just as courses in relativity often discuss the alternative theories I mentioned above to illustrate how rational inquiry works in science). But teaching "intelligent design" in biology classrooms as a genuine "dissenting view" would not accomplish that objective; rather, it would undermine it. Using disagreements over small details of evolutionary theory to argue that "intelligent design" should be considered as an alternative would be like using disagreements over small details of geography to argue that we should consider as an alternative the theory that the Earth is flat.


As I noted after the link to this article on this category's main page, Reason Magazine has posted an article about this issue. Here's a copy of my letter to the editor about that article.

To The Editor:

I read Reason Online's article "Sticker Shock" about the lawsuit by parents in Dover, PA, against the school board which voted to include "intelligent design" in its science curriculum. As usual, Reason took a viewpoint that had not been addressed in other commentary I've seen, and that was well worth some thoughtful consideration. This is why I like to read Reason's articles, even when I don't agree with them; unfortunately, the article in question is one such article.

The article argues that the real problem is our system of public education, which can't possibly respect everybody's beliefs, so the question is not creationism vs. evolution but "who gets to impose their beliefs on whom." I agree that the public education system can't respect everybody's beliefs, but I can't agree with Reason that this is a problem where science classes are concerned. I'm all for parents being able to teach their children their beliefs, not somebody else's, but that should be the job of the parents, not the public schools. It certainly shouldn't be the job of public school science classes. What should be taught in science classes is what the current scientific consensus says should be taught. The current scientific consensus is that "evolution is both a theory and a fact", as your article notes, and that "intelligent design" is not a scientific theory at all. Parental beliefs simply don't come into it.

Reason makes the analogy with an imaginary public food program, which takes in tax money and buys food for the entire community based on the selections of a "Menu Board". Clearly we wouldn't want the government interfering in our lives like that. But the case of education, at least science education, is not analogous. People choose the foods they eat for many reasons, of which nutrition (the only possible "objective" basis for a "Menu Board"'s selections) is only one. People's tastes differ, again for many reasons, and we accept the idea that there is no one "objectively best diet" that works for everybody. But science is not like that; there is such a thing as an "objectively best theory" in a given scientific discipline, and the job of scientists is to find it. Similarly, there is an objective standard for what counts as science in a science classroom, and the job of science teachers is to teach it.

Reason also mentions the "liberal ideals of tolerance and neutrality", without regard to their real meaning in this context. Those ideals were never meant to support relativism about matters which are objective, such as scientific fact. Tolerance and neutrality are appropriate when dealing with matters about which reasonable people can rationally disagree, but the current scientific consensus is that evolution is not such a matter. Tolerance and neutrality are also appropriate in social situations where politeness and avoiding confrontation about people's beliefs are more important than the search for truth. Does Reason really want to argue that schools should set their priorities in science classrooms this way?

Finally, Reason suggests that we might take a lesson from the theory of evolution by natural selection and not constrain our public education system to "a relatively uniform model of curriculum and pedagogy," but try out different things and see what works. As a defender of science and evolution, I can hardly take exception to this as a better idea for figuring out how to teach. But the same logic does not apply when determining what should be taught--at least, not in science class. The theory of evolution has already gone through just such a process of trial, error, correction, and improvement during the last century and a half since Darwin. To have our children study that history and see how it illustrates that process would be a wonderful thing in our schools; to have that study impel more children to pursue science and become scientists would be even better. But to try to make the schools themselves into a microcosm of that process with respect to the science curriculum would be to throw away all the hard-won knowledge that the scientific method has already given us.

(I should comment briefly on a couple of aspects of the above letter. First: as the opening paragraph notes, in the Dover, PA case it was the school board that voted to include intelligent design in the curriculum, and parents who sued the school board to have that reversed. However, as the next paragraph implies, it is often the other way around: parents want intelligent design to be taught, and school boards that are aware of the scientific consensus on evolution try to resist such pressure. Either way, the main point stands.

(Second: I should clarify my position about the current public school system vs. possible alternatives like school vouchers, which the Reason article discusses. I'm not against such a system per se--in fact, I agree with Reason that it would probably work better than our current system. Where I differ is over why that would be true. Reason argues that vouchers would give parents the freedom "to put their children's education in the hands of schools that reflect their beliefs, not the beliefs of school boards, curriculum committees, and the teachers unions." By contrast, I think vouchers would give parents the freedom to choose schools that determined what to teach children based on what was true, not on what was desired by school boards, curriculum committees, teachers unions, or even the parents themselves. In my vision of such a system, schools would compete based on real-world results; parents would know how good a school was by how well it prepared children to achieve further goals, such as earning a college degree or succeeding in a trade. In the vision articulated in the Reason article, parents would know how good a school was by how well its teachings matched their beliefs on any given subject, regardless of whether or not those teachings actually led to better real-world outcomes. Put this baldly, I doubt if the writer of the Reason article would agree that that was what a voucher system was for, but of course that was the point of my writing the letter.

(One final clarification: of course choosing what to teach based on what is true is not the goal in all subjects; I gave that as a criterion above only because it is the goal in the particular subject area in question, namely science. In other subject areas--literature, for example--the goal may be to learn about, discuss, and argue for or against the prevailing critical opinion. In still others--such as English composition and various skilled trades--the goal is to develop technical skill and understanding in the subject area. However, the more important point still remains: in the end, the test of whether the school has done its job is real-world outcomes, not comparison with some set of received beliefs.)


I used the phrase "a fair presentation of the issue" above, and I want to briefly discuss here the can of worms that that phrase opens up. As I note in the main article, intelligent design creationists often say that all they want is for children to get "a fair presentation of the issue", and then go on to claim that such a presentation would have to include intelligent design creationism as one alternative. My answer in the article was simply that, since intelligent design creationism (IDC) isn't a viable scientific theory, it doesn't deserve to be included in a fair presentation of the issue. You might have thought of a counter to this argument: even if IDC isn't a viable scientific theory, might it still not be of value to discuss it with kids in order to illustrate why? Shouldn't a fair presentation of the issue include the reasons why competitors to the current scientific consensus have lost out?

This sounds nice and open-minded (there's that phrase again...), but the problem with it is that you don't know when to stop. After all, IDC is by no means the only "competitor" theory to Darwinian evolution that has appeared on the stage. Do we have to discuss them all to give a fair presentation of the issue? Furthermore, discussing the reasons why IDC is not a viable scientific theory will take you into pretty deep questions about science and the philosophy of science; do you really want to clutter up a basic presentation of science in schools with such issues?

Here's an analogy to illustrate what I mean. When we teach kids arithmetic in elementary school, we assert a lot of propositions that we don't take the time to prove. For example, we tell kids that addition is commutative. We don't bother to prove this, even though it can be proved from much simpler assumptions--it's not something that just has to be assumed, although many people probably think it is. We don't bother doing this with kids (and most adults don't bother digging into it either) because the full proof of why addition is commutative would involve presenting the full axiomatic formulation of arithmetic, which involves some deep concepts of set theory--not to mention that you would have to first justify to the audience why going through all this rigmarole for something which is, pragmatically speaking, perfectly obvious, is actually a good idea, which is itself a deep philosophical question that many, perhaps most, people just don't care enough about to make it worth the time.

Now suppose that someone comes along and starts a movement clamoring for "equal time" for the claim that addition doesn't *have* to be commutative-that, in fact, the mathematics "establishment" is actively suppressing the "theory" that addition may not be commutative. And suppose this movement gets taken up by parents and school boards across the country, who demand a "fair presentation of the issue" in the schools, one that isn't "biased" towards the theory that addition is commutative. What should we do? Should we muddle up our simple presentation of arithmetic in school with all the esoterica of set theory, axiomatic formulations of mathematics, and so on, in order to ensure that children get a "fair presentation of the issue"?

(NOTE: I am aware that there are actually some mathematical systems in which addition is not commutative; however, none of them are anything like ordinary arithmetic, and they aren't really useful for anything outside theoretical mathematics. There are mathematical systems that get heavy use in physics where multiplication is not commutative, but addition still is in these systems. So in practical terms, just bluntly asserting that addition is commutative is pretty safe. However, I did want to mention explicitly that I don't intend an exact or complete analogy between the scenario I describe above and the real-world scenario with respect to evolution and intelligent design creationism.)

The upshot of all this is that no, a "fair presentation of the issue" does not mean that every competitor gets equal time. Kids who are interested enough will have plenty of opportunities to get more details about how evolution came to be the dominant theory, and why none of its competitors hold water. But when you present a basic area of science, you present the basics: the current scientific consensus. We don't present flat earth theory, or the phlogiston theory of combustion, or the caloric theory of heat, or the Ptolemaic theory of astronomy in basic science classes. Kids who are interested can always find out more about these subjects, but we don't clutter up a basic science class with them. The analogy with biology should be obvious.


One of the underlying themes of this topic (creationism vs. evolution) is the relationship between science and religion, and to be sure my position is clear I should discuss that more general theme here, separately from the specific topics addressed in the rest of this article. Many scientists, philosophers, theologians, and just plain people have weighed in on this topic, so it probably seems pretty complex to a reader confronting all this material. However, I think this is an illusion. I think the issue is actually very simple. It is this:

Religion believes it has eternal, immutable answers. Science doesn't.

What do all religions tell you? They tell you they know something with certainty. They tell you they know, for sure, no chance of error, that God exists; that Jesus is the Son of God; that Mohammed was a divinely inspired prophet; that Israel is the Promised Land, given by God to the Jews; that pain, matter, and suffering are unreal; that souls are reincarnated; that cows are sacred; that pigs are unclean; and so on. No one religion tells you all of these things, of course. Each one picks and chooses. But whichever "truths" each religion picks and chooses, it considers them eternal, immutable, known for certain without chance of error.

Of course, this trait is not confined to religions. One could argue that atheism is just as dogmatic, just as certain it has the eternal, immutable truth--it's just that the "truth" this time is that God does not exist and all religions are simply mistaken. But this conviction of certainty extends much wider than just religious matters, whichever side you take on those. Believers in various pseudosciences have the same attitude toward their beliefs. They tell you they know, for certain, no chance of error, that ESP exists; that astrology works; that aliens have visited Earth; that putting a pyramid under your pillow will make you smarter; that everyone has had past lives; that someone can bend spoons without touching them. Again, no one believer tells you all of these things; they pick and choose, and often a believer in one thing will laugh as derisively as a scientist at the "misguided" beliefs of a believer in some other thing. But they never catch on to the idea of taking the same skeptical attitude toward their own beliefs.

But taking a skeptical attitude toward one's own beliefs is an integral part of science. What do scientists tell you? Do they tell you they know things for certain? Often the media misquotes them that way, probably because that habit of thought is so widespread, having been touted by religions and pseudosciences and snake oil salesmen for thousands of years. But if you listen carefully, you will always hear qualifiers. -- "To the best of our knowledge..." -- "It's extremely unlikely that this research could be mistaken..." -- "The consensus of scientific opinion is..." -- A scientist will never tell you he's flat out certain of anything (unless he's an expert witness paid by a party in a court case, and even then if he's honest he'll hedge).

Note carefully that this is not the same as skepticism toward other people's beliefs. It is not the same as the attitude scientists take toward pseudoscience or quackery--or dogmatic religion, for that matter. Skepticism toward other people's beliefs just means not taking what they say for granted, checking up on factual assertions, examining the logic, and so forth--straightforward critical analysis skills. If scientists don't always seem ready to hop to it and apply these skills to the latest pseudoscientific craze, it's probably because just hearing the description of the nonsense was enough to enable them to conclude with reasonable assurance that it was nonsense and not worth more detailed scrutiny. (Or, of course, they may already have heard it a hundred times and seen it refuted.)

Skepticism toward your own beliefs is something more difficult. It means not being 100% certain of something even if you yourself can't see anything wrong with it--even if you yourself have examined it in detail and agree with it. No matter how attractive the belief seems, no matter how much you like it, no matter how much it makes you feel smart and happy, it's not really worth much until it's been looked at by others, preferably others who don't find it as attractive as you do, and tested. Even Einstein, who was supremely confident that general relativity was correct before it was experimentally tested, had had the theory examined by others: primarily David Hilbert, arguably the greatest mathematician of the time. It was largely the fact that Hilbert, much more mathematically knowledgeable than Einstein (he commented after the field equation had been published that "every schoolboy in the streets of Gottingen [his university's town] knows more geometry than Einstein"), discovered an alternate derivation of Einstein's field equation--one which was much more elegant and succinct than Einstein's--that made general relativity look worthy of assent.

And even after a scientific theory has reached the pinnacle, has been verified many times and accepted by scientists throughout the world, it can still not be 100% right. Newtonian physics was accepted by all physicists for more than two hundred years, and was successful in solving thousands of problems, such as predicting the orbits of astronomical bodies. Then relativity came along, and physicists realized that Newtonian physics was not quite right, that it was really just a special case of relativity applicable when the speeds were small compared to that of light and gravity was weak. Today we have general relativity, which gives correct answers over a far wider range, but still is not quite right. We know it's not quite right because it's not a quantum theory--the next step is a quantum theory of gravity, which is a hot topic of research today.

It is experiences like this, repeated many times in many different fields, that have made scientists understand the value, the necessity, of not being 100% certain about anything. The fact that science doesn't have eternal, immutable answers is not just because scientists haven't gotten smart enough yet. It's a fundamental property of science; it's a fundamental attitude of the scientific worldview that we humans are fallible, that we don't get it perfectly right, that there is always room for improvement in our theories and our beliefs. This is the fundamental difference between science and religion.

This difference is not trivial. Not being 100% certain of anything is not a bad thing; quite the contrary. It's what enables freedom of thought. If everyone thinks we already have all the right answers, no one is motivated to search for new ones. Richard Feynman, in his essay The Value of Science, puts it this way:

If we suppress all discussion, all criticism, proclaiming "This is the answer, my friends; man is saved!" we will doom humanity for a long time to the chains of authority, confined to the limits of our present imagination.

Religions will say, of course, that they don't want to constrain freedom of thought. They want new ideas; they want new thoughts about how we can better know God (assuming the religion in question considers that important--I can't talk generically about all religions because, as I noted above, they all have different beliefs, so I'll have to use the Judeo-Christian belief system as an example). But religions always put a limit on this process. We can look for better ways to know God, but we can't doubt that there is a God, or the foundation of the religion is gone. In the case of Christianity, the same applies to Jesus: we can look for better ways to know Jesus or to understand his message, but deciding that we were mistaken in believing that he's the Son of God is not an option.

In science, however, no belief is immune from being found to be false. No theory is immune from revision, even of its fundamental principles. I said above that Newtonian physics is a special case of relativity, which makes it sound like relativity was really just an expansion or generalization of Newtonian physics to cover a wider range of cases. This is often a fruitful way to look at it, because (as I noted in the article above) it frees us from the need to say that Newtonian physics is "wrong". How can a theory be wrong when it correctly predicts so many phenomena, from the fall of an apple from a tree to the motions of heavenly bodies? But there is no question that the conceptual foundations of relativity are completely different from those of Newtonian physics. Newton based his physics on absolute space, absolute time, and a simple view of matter as indestructible particles in motion and forces like gravity as unanalyzed interactions between those particles. Einstein based relativity on the postulate that space and time are observer dependent, and the only invariant is the four-dimensional spacetime manifold--and that gravity is the curvature of this manifold. So the fundamental conceptual foundation of Newtonian physics was false, even if it got the right answers. Saying that Newtonian physics is a special case of relativity is really saying that, from the relativistic equations, you can show why the Newtonian equations give the right answers when they do--it is not saying that the concepts of both are the same.

Furthermore, religions, however much they say they want new ideas, in practice are actively hostile to them. This is not the same as the reasonable skepticism that scientists bring to new ideas. It is not hostile to run a basic consistency check on a proposed new belief or theory to see how it fits in with existing ones. If the check flags a problem, particularly if it is an inconsistency with something that's been thoroughly tested, the scientist will probably reject the new idea out of hand, but that's not hostility, it's just common sense. Scientists don't spend a lot of time reviewing detailed plans for perpetual motion machines, but that's not hostility; something that fails a consistency check with the law of conservation of energy just isn't worth a further look, because that law has been so thoroughly tested that it's extremely unlikely to be wrong. (Not certain to be right; just extremely unlikely to be wrong. Nobody has succeeded in getting around it. [4])

Science's skepticism of new ideas is based on common sense and probabilities, just like its treatment of all ideas. A belief that isn't certain can still be extremely likely to be true, and a belief that isn't definitely false can still be extremely likely to be false, and there are no limitations on examining evidence and logical consistency to determine where on the spectrum a particular belief falls. But religion, since it has to view some beliefs as absolutely certain, immune to error, is naturally hostile toward other beliefs that aren't consistent with those immutable beliefs. If the other beliefs have evidence in their favor, then that evidence has to be actively suppressed, to avoid putting doubt into people's minds. And if some people refuse to accept this, if they persist in calling the evidence to people's attention and questioning the immutable beliefs, they must be stopped by whatever means are necessary. Nowadays it is usually enough to denounce them in the press and make a few unsavory accusations about their personal lives. In the past sterner measures were necessary; Galileo was placed under house arrest by the Inquisition, and Giordano Bruno (who claimed that there were other worlds orbiting other stars besides the Sun) was burned at the stake.

You may think I'm making too much of this last point. Churches don't burn people at the stake nowadays, do they? Perhaps not, but that's just a sign of changing times and changing tactics, as I noted above. Burning at the stake is unpopular today, but there are plenty of other tactics available--like co-opting school boards. People say they just want children to get a "fair" presentation of the issue in school; but as I showed in the article above, "intelligent design" would not be part of such a presentation. What those people really want, whether they realize it or not, is to insulate children from a fair presentation of the issue, because a fair presentation of the issue would convince them that the theory of evolution has a very high probability of being correct. It's not 100% certain, but it's about as certain as it's possible to get in science. And, as I noted, even if evolution turned out to be wrong, "intelligent design" creationism wouldn't be what replaced it, because a fair presentation of the issue would also convince children that "intelligent design" is nonsense as a scientific theory. It's so unlikely to be true that it is foolish to believe it. But people who believe that their religion has a certain answer to the question of how humans got here, and it isn't the same answer as evolution gives, can't allow this to take place. As Feynman said, they want to confine their children to the limits of their (the creationists') imaginations.

It is true that this distinction I'm making, between science's treatment of all beliefs as always subject to revision and religion's treatment of some beliefs as immune to revision, can seem paradoxical. I started out by saying that science is never 100% sure of anything, but at the same time I'm sure enough that evolution is right to reject "intelligent design" out of hand as an alternative theory. If science is never certain, how can I be so sure that evolution is right, so confident that I can reject out of hand the idea that an "alternative" theory should be taught also? More generally, how can a science that admits it's never certain of anything still manage to undermine belief in religious propositions that are supposedly immune to error?

There are two answers to this. The first, simpler one is that I'm not rejecting "intelligent design" as an alternative because of what I believe about evolution; I'm rejecting "intelligent design" because of its own inadequacy as a scientific theory. As I noted in the article above, in principle anyone can contribute a new scientific theory, but to do so you have to play by the rules, and the rules are more basic than any particular theory; they're based on our empirical knowledge of what has worked and what hasn't in coming up with theories in the past. Since "intelligent design" as a putative scientific theory doesn't play by these rules, it ought to be rejected regardless of whether we have another theory (evolution) that does a better job. Applying this same reasoning to the more general question I posed above, just because religions say their beliefs are immune to error doesn't mean they really are; common sense alone is enough to tell us that human beliefs are never that infallible.

The second, more profound answer is that science, unlike religion, recognizes that you don't have to be absolutely, 100% certain of a belief in order to act on it. I'm not absolutely certain that the sun will rise tomorrow, but I'm sure enough to plan for it. And I'm at least as sure that evolution is true as I am that the sun will rise tomorrow, so why shouldn't I treat my belief in evolution the same way as I treat my belief that the sun will rise tomorrow? I don't have to be absolutely certain--just certain enough to act on it. However paradoxical it may sound, it is science's very admission that it isn't 100% certain of anything that allows us to gain knowledge, in the sense that really matters: the practical knowledge that can serve as a good guide to action. However strange it may seem to religious minds, the history of science shows that the best way to figure out what to do in a given field is to gain scientific knowledge in that field.

Take, for example, the history of medicine. Quite apart from the ancient and medieval secular theories of disease, religions have had plenty to say on how to prevent or cure diseases. The touch of a holy man, or prayer and fasting, or just having sufficient faith was supposed to be enough to effect a cure. But it wasn't until science was applied to the theory of disease, first by Pasteur and Koch in the nineteenth century, that real, effective cures for diseases became widely, systematically available. That wasn't because Pasteur, Koch, or anybody else researching the germ theory of disease found immutable truths about disease that were immune to error. Quite the contrary: we now know that there are important diseases which are not caused by germs (for example, diseases like Down's syndrome which are due to genetic problems). But that didn't matter, because Pasteur and Koch and all the others never claimed they had all the answers. And that didn't prevent the answers they did find from working.

Perhaps religion is willing to recognize science's ability to find real, workable answers in a field like medicine (though some sects, such as the Christian Scientists, still refuse to do so today), or physics, or chemistry. But again, religion always has to draw a line somewhere--there always have to be some beliefs that are absolutely certain, immune to error. To the school board in Dover, PA that voted to include "intelligent design" in the curriculum, there is such a line in the field of biology. To other religious groups, there is no line there, but there are still lines elsewhere. And ultimately all religions have to draw the line at some basic belief like the existence of God. But science recognizes no such lines; even beliefs about the ultimate questions of existence are subject to revision.

This is, in the final analysis, what religions can't understand about science: how someone can possibly live without answers to the ultimate questions. But it's not only possible, it's essential. Another quote from the Feynman essay on the value of science illustrates what I mean:

[W]e scientists...take it for granted that it is perfectly consistent to be unsure, that it is possible to live and not know. But I don't know whether everyone realizes this is true. Our freedom to doubt was born out of a struggle against authority in the early days of science. It was a very deep and strong struggle: permit us to question -- to doubt -- to not be sure. I think that it is important that we do not forget this struggle and thus perhaps lose what we have gained.

"It is possible to live and not know"--meaning not know for sure, without possibility of error, even about the ultimate questions of existence. Perhaps that prospect is why so many people find it hard to accept science for what it is. They can't accept that it is possible to live and not know for sure, that the best knowledge we can have, even about our origins, our place in the universe, and the purpose of our existence, is the fallible knowledge that science gives us. But that fallible knowledge, imperfect as it is, is the best guide to action we're going to get. It's where our best hope lies for the future, and that being so, it's what we ought to be teaching our kids.

A Final Note. I want to briefly address another issue that's not strictly relevant to this article, but is relevant to the more general question of the relationship between science and religion. This issue has to do with the point of view that says science and religion are not at odds because they're different ways of knowing; the phrase currently in vogue is "non-overlapping magisteria". A number of prominent scientists, such as Stephen Jay Gould, have advocated this viewpoint. (Gould, who was an atheist, probably did so mainly to try to get better results at keeping religion out of his hair, but that's another article.)

It should be obvious that such a viewpoint isn't strictly relevant to this article, because any religious person who thinks science and religion are different ways of knowing, each valid within its own sphere, is not going to try to argue against the theory of evolution. Why should they? They would simply say that evolution is God's way of implementing his plan, and science can't tell us about God's plan, because that's only accessible to the religious way of knowing--it's in the religion "magisterium", not the science "magisterium". Science can tell us only about facts; it takes religion to tell us about values (or morals, or ethics, or whatever word you want to use).

This sounds good to scientists like Gould, but the trouble is that most of the religious people I know would be quite surprised to hear it claimed that their religion doesn't have anything to say about facts. Surely the existence of God, if He exists, is a fact. Surely Jesus rising from the dead, if it really happened, is a fact. It's hard to see how such propositions can be part of a different "magisterium" than the proposition that evolution happened. Certainly the people on that Pennsylvania school board who voted to have "intelligent design" taught didn't think their religion had nothing to say about facts. (Please note that I'm not trying to say that most of the religious people I know are creationists. [5])

I agree with the members of that school board, and religious people like them, that the dispute is not about which "magisterium" we are dealing with, but about plain facts like whether evolution happened. I disagree with them on the answer, but I don't disagree with them on the nature of the question. I don't think there are different, mutually exclusive, "ways of knowing". There's only one way of knowing, the way that lets you know the truth. I realize that there are people who don't accept this--there are "religious liberals" who think their religious beliefs don't have to be consistent as long as they make you feel good, philosophical relativists and postmodernists who deny that there is such a thing as objective truth, pseudoscience adherents who just can't accept the fact that their theories are no good if they're inconsistent with the rest of science. I just have no patience with them. It would be nice if everyone understood what science is and why we need it, but if I have to have disagreement, I'd rather have a plain honest disagreement with someone who at least accepts that there's something real to disagree about.

Religious liberals are in one sense even farther in spirit from scientists than are fundamentalists and other religious conservatives. At least the conservatives like the scientists tell you that they believe in what they believe because it is true, rather than because it makes them good or happy...Wolfgang Pauli was once asked whether he thought that a particularly ill-conceived physics paper was wrong. He replied that such a description would be too kind--the paper was not even wrong. I happen to think that the religious conservatives are wrong in what they believe, but at least they have not forgotten what it means really to believe something. The religious liberals seem to me to be not even wrong.

Steven Weinberg
Dreams of a Final Theory


[0] - Please note that in this article, when I use the term "intelligent design", I am only talking about the version that is creationism dressed up as science. This should be obvious from the context--after all, I talk herein about a version of "intelligent design" that isn't just creationism dressed up as science, the idea that life on Earth was started when the planet was "seeded" with microbes from outer space--but I mention it here to forestall the inevitable complaints about the ambiguity of the term "intelligent design". If you subscribe to the idea that aliens "seeded" Earth with microbes several billion years ago and then left it to ferment as it would, I'm not arguing against you in this article--but I do note, later on in the article, that this explanation only pushes the question back a step, because you still have to explain where the aliens came from that were capable of doing the "seeding". See that discussion (right after the paragraph linking to Footnote 1) for more.

(By the way, in case you're wondering why this footnote is numbered 0 instead of 1, it's because I'm too lazy right now to go back and re-number them all since I'm adding this one at the front. So sue me.) back to text

[1] - The claim about "irreducible complexity" also reveals another intellectual weakness of "intelligent design"--it begs the question of where complexity originally came from. Evolution is a scientific account of how complexity can arise from simplicity, given the right conditions, which we have good reason to believe have been present on Earth during the 4.5 billion years of its existence. The "irreducible complexity" argument just assumes that complexity exists, without explaining where it comes from--the claim that "complexity comes from the designer" is not a real explanation because it begs the question of where the designer's complexity comes from. That's not to say that complexity has to have an explanation: it's always logically possible that complexity has no explanation, that it's just a brute fact of the universe. But it's disingenuous to maintain such a position when there is a well-tested scientific explanation for complexity that doesn't require it.

Here's another more striking way to put this point: even if we grant for the sake of argument that living things have "irreducible complexity", that doesn't make intelligent design any better as a theory, because if living things have irreducible complexity, and irreducible complexity means something had to be designed, then surely the designer--who has even more irreducible complexity--must have been designed too! (This article on the CSICOP website goes into this point in much more detail.) So either we have an infinite regress of "designers"--after all, whatever designed the designer also has to be designed, and so on ad infinitum--or there have to be some things that can have "irreducible complexity" without being designed. And once you admit that, it certainly seems superfluous to introduce a designer to be the thing that can have irreducible complexity without being designed, when we already have a theory that can explain how the "irreducible complexity" we already see in the world around us could have come into being without being designed.

This point also illustrates why the theory of evolution was such an intellectual breakthrough. Before Darwin, if you encountered something that looked like it was designed, the only viable hypothesis known that could account for such a thing was that it was designed. This is the point of Paley's famous argument about the watch implying a watchmaker. Of course Paley and his followers never let on (probably because they didn't realize) that there is a logical flaw in the watchmaker argument, the one we have just been discussing; but up until Darwin came along, even people who were convinced that something was wrong with the argument couldn't do much about it because they had no alternative to offer. Darwin's great contribution to human knowledge was to provide such an alternative--that is, he provided another viable explanation for things that look designed, one that didn't require the existence of a designer. And once this idea is out there, it can't be taken back--it can never again be validly claimed that there must be a designer somewhere because there is no alternative that can explain the complexity we see in the world.

(By the way, this feature of Darwin's ideas is actually quite general, and can be applied to fields very different from biology. This is why Daniel Dennett, in Darwin's Dangerous Idea--which I'll refer to again in note 3 below in a similar connection--called Darwin's insight a "universal acid" that changes everything it touches. Perhaps its generality and power is one reason why so many ideologues in various fields are afraid of it.) back to text

[2] - You may wonder how I can possibly justify such a grandiose-sounding claim. Actually it's not grandiose at all: it's simply an illustration of how stringent the conditions are for a theory to become part of the "current scientific consensus", how much weight we ought to give the claims of such a theory once it has passed the tests, and how unlikely it is that those claims will turn out to be wrong. Scientific consensus on any theory takes many years and many experiments and many skeptical challenges to build. It doesn't come easily, and it doesn't come often. That's why it carries so much weight once it's reached. Historians of science who seem to be claiming that it's easy for the current scientific consensus to be wrong are simply misrepresenting their material: they are claiming that a scientific consensus was proved wrong, where in fact there was either no real scientific consensus in the first place (e.g., the case of Galileo--what he proved wrong was not a scientific consensus but a religious dogma) or there was a consensus that did not get proved wrong, but simply refined and expanded (e.g., the case of Einstein and relativity refining Newtonian physics, which I discuss next). Both of these errors are committed often by "intelligent design" advocates who misread both the history and the current state of evolutionary theory. back to text

[3] - Some purists would object to my terminology here; they would say that life getting started on Earth in the first place is "abiogenesis" (life coming from non-life), while "evolution" refers only to the development and diversification of life after it got started. However, a number of scientists and philosophers (for example, Richard Dawkins in The Blind Watchmaker and Daniel Dennett in Darwin's Dangerous Idea) have argued that the chemical process by which life got started operates according to the same rules as evolution (variation among entities that replicate, causing differential success in replication) and therefore can rightly be called by the same name. (They also argue that the same process operates in other media, such as culture--Dawkins calls the replicators in this medium "memes"--but that's beyond the scope of this article.) That's the view I'm taking here, but I should note that doing so is not in itself a challenge to "intelligent design" proponents, because they themselves implicitly assume it: they spend as much time arguing against scientific theories of abiogenesis as they do arguing against the theory of evolution proper, and they clearly believe that these arguments are all of a piece. (For example, the first "piece of evidence" I cited above, about the supposedly too-low probability of life-supporting molecules like DNA arising on Earth by chance, is really an argument against abiogenesis.) And even purists would agree, I think, that however we divide up scientific theories for ease of discussion, science is still ultimately all one enterprise, and science's unity in the face of irrational opposition like "intelligent design" creationism is far more important than its diversity of opinion about some details. back to text

[4] - And what about the rare cases where the person who goes against the scientific consensus is right? Some people just can't help getting hung up on this point. They view every crackpot who thinks he's got a design for a working perpetual motion machine as a potential Galileo or Einstein. But if you look at the cases like that of Einstein where somebody really did make a fundamental change in a scientific paradigm--or like that of Galileo, where somebody did make a fundamental change in a paradigm, but it wasn't really a scientific one (as I noted in footnote 2 above)--what actually happened isn't very comforting to the hordes of perpetual motion machine designers. First of all, Galileo and Einstein and the others like them always attacked where the current paradigm was weak, not where it was strong. Einstein didn't bother trying to attack the law of conservation of energy, even though it turns out that in general relativity the concepts of energy and energy conservation are actually problematic in certain contexts. (For example, there is no clear way to define the "total energy of the universe" in general relativity. Don't go thinking perpetual motion is possible after all, though: none of these issues affect the well-established fact of local energy conservation, which is what would have to be violated to make such a device.) Einstein zeroed in on the place where Newtonian physics was inconsistent with Maxwell's Equations--the absoluteness of space and time. Second, Galileo and Einstein and the others like them knew intimately the paradigms they were trying to overthrow. Einstein was able to zero in on the absoluteness of space and time because he understood the physics of his time so well that it was obvious to him that that was where to look. When a present-day scientist rejects out of hand a proposed design for a perpetual motion machine, he's doing it not just because it fails the consistency check with the law of conservation of energy, but because that very failure, absent an extremely convincing explanation (which has never yet been forthcoming), indicates that the perpetrator fails the other two tests as well. back to text

[5] - Please note also that the only plain facts that I'm disagreeing with religious conservatives about here are those about whether evolution happened. I don't agree or disagree with them about the plain fact (if it is a fact) of God's existence because I'm an agnostic, not an atheist. Just because a question is about plain facts doesn't mean you have to commit yourself to an answer. Religious conservatives would also disagree with that statement; they would say that you do have to commit yourself--or, more precisely, that people who say they haven't committed themselves actually have, even if they don't realize it; that people like me who say they're agnostics are really de facto atheists. It should be obvious by now that I don't subscribe to that point of view either. back to text


Intelligent Design and Unintelligent People: An article on various logical holes in ID. (Note that it also points out faults in the way scientists handle the issue, and I do not disagree with those observations. Scientists don't have any more right than anyone else to make unsupported claims--I make claims in this article, but I've tried to support them. I've also tried to give a few decent reasons why scientists aren't always thrilled to discuss the support for their claims with the ignorant--but I'll admit there are also plenty of not so decent reasons out there.)

Why I Am Not A Christian: The famous speech by Bertrand Russell. One of the topics he addresses is the Argument from Design.

Understanding Evolution: A site run by UC Berkeley; lots of good general info about evolutionary theory and why it's as well accepted as it is. This site has a Controversy FAQ which has a specific entry about intelligent design; this entry gives good short presentations of the major "arguments" for intelligent design given by key proponents, along with cogent refutations by working biologists.

Evolution, Creation, and Science Education: An article on the National Center for Science Education website on why evolution should be taught in schools and "scientific creationism" shouldn't.

Show Me The Science: A piece by the philosopher Daniel Dennett (whose Darwin's Dangerous Idea, by the way, I highly recommend if you want a detailed layman's presentation of the basics of the theory of evolution) discussing the fact that ID hasn't offered any actual scientific evidence or testable hypotheses.

Can We Please Retire The "ID Isn't Science" Meme?: A post by Jason Rosenhouse on his blog that contains the following salutary quote:

The primary scientific criticism of ID is that the specific assertions made by ID folks, about irreducible complexity, complex specified information, the alleged holes in evolutionary science, and so on, are universally false. That's why scientists reject ID.

He goes on to explain in more detail why this observation is important. I reference it here to make explicit that, although I do say "ID isn't science" in the article above, I agree with Rosenhouse that that's not the primary criticism to make--the points he lists (all of which I refer to above) are the primary ones, and the observation that "ID isn't science" but just religion dressed up to look like "science" only comes in after you're satisfied on those other grounds that ID is false. ID proponents may well complain about this, but in fact this viewpoint is the respectful one for scientists to take, because it recognizes that if any of the critiques made by ID proponents were true, then they would indeed have a genuine challenge to evolution, whether their ultimate motives were religious or not. They don't have such a challenge because their critiques are false, pure and simple.

(I should also note that, even so, there is an additional question of whether, even if ID is false, it might be worth discussing in science classes why it is false. I address that point in the above article as well: such discussions might indeed be worth having, but not in science class. For that issue, the observation that "ID isn't science" is relevant--but again, the whole question is secondary to the question of what is the best scientific theory of life on Earth.)

Some Additional Thoughts

(April 2008) Ben Stein's movie Expelled has just come out, and it turns out to be a "documentary" (the word is in scare-quotes advisedly--see the note below) about how "Darwinism" has taken over the science of biology, unfairly driving out alternative viewpoints, causing supporters of those alternative viewpoints (i.e., Intelligent Design) to be persecuted and ostracized, and undermining belief in God. (And this is by no means all: the movie also claims that Darwinism leads to totalitarian dictatorships. Probably it also causes cancer in laboratory animals, and who knows what else. But I digress.) I'm not going to bother refuting those claims directly here--if the article above, and the sources it links to, and all the myriad additional sources you will find on the subject if you keep following links (not to mention the many books and scientific papers in the field) are not enough to convince you that Mr. Stein and his movie are, to be blunt, utterly full of it, then any additional attempt on my part here would be futile. Here I just want to talk about a train of thought that reading about the movie prompted me to follow.

The train of thought started with the observation that the situation portrayed in the movie in biology--"Darwinism" as a ruling orthodoxy that controls all science in its field and persecutes any dissenters--is not unlike the situation portrayed in current climate science by those who are skeptical with regard to global warming. I won't go into detail about this situation here either--I discuss some aspects of it in my article on global warming--because I'm not so much interested in the details of either situation by itself, but in the comparison between the two: in this article, I maintain that Intelligent Design is not a credible scientific theory, and its demands for "equal time" do not deserve to be honored, whereas in my global warming article, I maintain that there is a credible dissenting position; there are arguments on both sides that deserve consideration, and attempts by one side to silence the other (which, arguably, has taken place in climate science) are not justified. In other words, I believe that if a similar movie to Stein's were to be made by global warming skeptics, making similar claims, it would be a justified criticism of climate science--whereas Stein's criticism of biology is most certainly not justified.

The obvious question, of course, is then: what's the difference? How is it that I can blithely claim that Stein's movie is baloney, while at the same time supporting similar claims in another branch of science? Another way of seeing the question would be to observe that, in one of my notes on the above article, I talked about the "current scientific consensus", and defended the claim that it has almost never been wrong; but isn't the belief in human-caused global warming a current scientific consensus? If it isn't, but Darwinism in biology is, then what's the difference? How do we draw the line and say that a given theory now counts as "the current scientific consensus" and deserves to be given the corresponding weight when judging claims?

Perhaps unfortunately, there isn't any cut and dried answer; but, as I said in the afterword to the above article, recognition of that fact is precisely what separates science from other forms of human belief. Because science is based on the belief that we don't know very much, that we get things wrong, that we must always be prepared to revise our theories, it sets a very high bar for "accepted consensus"--a bar that is very hard to clear. It's human nature not to want to go to that extreme, and giving in to that natural impulse is what leads to beliefs like Intelligent Design and premature declarations of consensus on global warming. It's so much easier to just stop striving and proclaim that your current beliefs are good enough. But however tempting this path is, it doesn't count as true scientific consensus; only those rare theories that are able to clear the high bar get to be treated that way. Darwinism in biology is such a theory, and that's why it has "taken over" the field. "Global warming theory", if I may call it so for the moment, has not cleared the high bar, and that's why it is still open to charges of suppressing justified dissent.

But in fact, this comparison is too kind to Intelligent Design; for, as I show in the above article, Intelligent Design, at least in its version as theology dressed up as science, is not a credible scientific theory regardless of the theoretical status of Darwinian evolution. (I make the caveat in order to leave aside "panspermia" theories, which I mentioned briefly in the article, that claim that life on Earth originally arose when microorganisms arrived here from space, "seeded" by intelligent aliens. The article shows why these types of theories are not germane to the present discussion.) This very fact gives us something of a rule of thumb for determining whether a theory in a given field might be worthy of "consensus" status: ask yourself whether any credible theory in the field would have to contain the basic germ of the theory in question. For example, general relativity in physics is such a "consensus" theory for this reason: physicists have shown that any theory that can explain the facts of gravity must look like general relativity, at least in the low-energy limit. And, as I hope I've shown in the article above, there are similar arguments to be made for Darwinian evolution in biology. But no theory in climate science is even close to having that kind of argument in its favor.

Note: I put the word "documentary" in scare-quotes above because, as the Expelled Exposed website (put up by the National Center for Science Education) makes clear, the movie not only gets the basic question of whether "intelligent design" is science wrong, and not only misunderstands the theory of evolution, but makes many factual claims that are just plain false. (For example, none of the claims of scientists being ostracized, suppressed, penalized, etc. for believing in "intelligent design" stand up to scrutiny.) Also, the makers of the film misled a number of pro-evolution people who appear in it, most notably Richard Dawkins, whose views are certainly misrepresented in the brief clip I saw on TV. (Dawkins has posted his own review of the movie, entitled Lying for Jesus?, which talks about the interview he did that was misleadingly excerpted in the film.) The bottom line is that the NCSE's conclusion is quite justified: this film is not in fact a "documentary" at all--it's a piece of anti-science, religious fundamentalist propaganda.

Michael Shermer's review in Scientific American: Shermer notes that the initial scene of the film, showing Stein addressing a cheering crowd at Pepperdine University (Shermer's alma mater) was staged; almost the entire audience was paid extras, not students, and the university did not sponsor the event.

Jason Rosenhouse's Review on his blog: one interesting item is that when he went to see the movie (in a town he describes as "how shall I put this? -- somewhat to the right of center politically"), there weren't many people there. One can hope that the lack of interest will continue, thus mitigating the damage the film could do if large numbers of people actually saw it and thought it was a genuine documentary.

Reason magazine's review.

(September 2008) Since I link to several articles by climate scientist Roy Spencer in my article on Pascal's Wager and Global Warming, I found it interesting that Spencer has also posted an article on the web about evolution and Intelligent Design. You might be surprised, given the fact that I generally agree with Spencer's position on global warming, that he takes a contrary position to mine on Intelligent Design. So, just to illustrate that even scientists don't get everything right, I'll give a brief rebuttal to his article here.

Spencer's argument is pretty well summarized by these two paragraphs from his article:

True evolution, in the macro-sense, has never been observed, only inferred. A population of moths that changes from light to dark based upon environmental pressures is not evolution -- they are still moths. A population of bacteria that become resistant to antibiotics does not illustrate evolution -- they are still bacteria. In the biological realm, natural selection (which is operating in these examples) is supposedly the mechanism by which evolution advances, and intelligent design theory certainly does not deny its existence. While natural selection can indeed preserve the stronger and more resilient members of a gene pool, intelligent design maintains that it cannot explain entirely new kinds of life -- and that is what evolution is.

Possibly the most critical distinction between the two theories (or better, "models") of origins is this: While similarities between different but "related" species have been attributed by evolutionism to common ancestry, intelligent design explains the similarities based upon common design. An Audi and a Ford each have four wheels, a transmission, an engine, a gas tank, fuel injection systems ... but no one would claim that they both naturally evolved from a common ancestor.

First of all, let's get one possible misunderstanding out of the way: common ancestry is an indisputable fact, and the theory of evolution does not just "attribute" the similarities between species to it; the case is much stronger than that. Spencer seems not to realize that there are other lines of evidence for common ancestry besides the fossil record (and even there he is wrong that the fossil record is "almost (if not totally) devoid of transitional forms"). There was plenty of anatomical and behavioral evidence for common ancestry even in Darwin's time (hint: not every feature is functional--an Audi and a Ford may have similar designs, but if you found a car that looked like an Audi but had a Ford emblem on it, you'd be inclined to suspect that something more than just convergent design was at work). But now that we have DNA evidence, it's an absolute slam dunk. It is simply not in question that every single living organism on Earth is descended from a common ancestor, so there is no need to invoke "common design" to "explain" their similarities.

But more importantly, Spencer's argument assumes that there is a fundamental difference between "micro" and "macro" evolution--between preserving the stronger members of a gene pool based upon environmental pressures and creating entirely new kinds of life. This is simply false. There is a continuous variation from small-scale evolution such as moths going from light to dark or bacteria evolving resistance to an antibiotic (and these are examples of evolution, whatever Spencer may think), through changes like dogs evolving from wolves over the last 10,000 years or so (and all of the other domesticated plants and animals we know), through the evolution of humans and chimpanzees from their last common ancestor about six million years ago, through the evolution of the first mammals from the therapsid reptiles about a hundred million years ago, all the way back to the evolution of everything else from a small initial population of replicators over the last few billion years. At no point along this spectrum can we draw a sharp dividing line between "micro" and "macro" evolution that is not arbitrary. (And, of course, as you will know from reading my article above, the initial small population of replicators itself arose by what we might call "chemical evolution" from nonliving molecules, so life itself is connected to the rest of the universe by chemistry and physics.)

But what about species? you may ask. Doesn't the "creation" of new species provide the sharp dividing line? No, because species are not absolute categories. We draw lines around particular groups of organisms and mark them off as a "species", isolated from all other species, but those lines are as arbitrary as any line we might draw between "micro" and "macro" evolution. This follows, of course, from the fact of common ancestry: every species is connected to every other via some common ancestor in the past, so none of them are really isolated. And there is no point along the line of common descent where you can say, "here is where the ancestor species stops and the descendant species begins"; that transition, too, is arbitrary, like the choice of where on the isthmus of Panama to draw the boundary line between North and South America. The fact that these categories are useful to us in thinking about the world does not mean that they are necessary parts of the world.