In response to a previous posting, commenter Sarah Taylor made several important points. She clearly articulated the view that evolutionary theory is a complex edifice that is built on many observations that fit into a general pattern that is largely chronologically consistent.

She also notes that one distinguishing feature of science is that there are no questions that it shirks from, that there are no beliefs that it is not willing to put to the test. She says that “What makes scientific theories different from other human proposals about the nature of the universe are their courage. They proclaim their vulnerabilities as their strengths, inviting attack.�

I would mostly agree with this. Science does not shy away from probing its weaknesses, although I would not go so far as to claim that the vulnerabilities are seen as strengths. What is true is that the ‘weaknesses’ of theories are not ignored or covered up but are seen as opportunities for further research. Since there is no such thing in science as infallible knowledge, there is no inherent desire to preserve any theory at all costs, and the history of science is full of once dominant theories that are no longer considered credible.

But having said all that, it is not necessarily true that finding just one contradiction with a theory is sufficient to overthrow the theory. In the context of the challenge to Darwinian theory by intelligent design (ID) advocates, Sarah’s statement that “All that any ID devotee has to do is to show ONE fossil ‘out of place’, to prove the theory doesn’t work. Just one horse shoulder blade in a Cambrian deposit somewhere in the world, and we can say goodbye to Darwinâ€? is a little too strong.

Sarah’s view seems to be derived from the model of falsificationism developed by the philosopher of science Karl Popper (see his book Conjectures and Refutations: The Growth of Scientific Knowledge), 1963) who was trying to explain how science progresses. After showing that trying to prove theories to be true was not possible, Popper argued that what scientists should instead do is try to prove theories false by finding a single counter-instance to the theory’s predictions. If that happens, the theory is falsified and has to be rejected and replaced by a better one. Hence the only status of a scientific theory is either ‘false’ or ‘not yet shown to be false.’

But historians of science have shown that this model, although appealing to our sense of scientific bravado, does not describe how science actually works. Scientists are loath to throw away perfectly productive theories on the basis of a few anomalies. If they did so, then no non-trivial theory would survive. For example, the motion of the perigee of the moon’s orbit disagreed with Newton’s theory for nearly sixty years. Similarly the stability of the planetary orbits was an unsolved problem for nearly 200 years.

Good theories are hard to come by and we cannot afford to throw them away at the first signs of a problem. This is why scientists are quite agreeable to treating such seeming counter-instances as research problems to be worked on, rather than as falsifying events. As Barry Barnes says in his T.S. Kuhn and Social Science (1982): “In agreeing upon a paradigm scientists do not accept a finished product: rather they agree to accept a basis for future work, and to treat as illusory or eliminable all its apparent inadequacies and defects.�

Dethroning a useful theory requires an accumulation of evidence and problems, and the simultaneous existence of a viable alternative. It is like a box spring mattress. One broken spring is not sufficient to make the mattress useless, since the other springs can make up for it and retain the mattress’s functionality. It takes several broken springs to make the mattress a candidate for replacement. And you only throw out the old mattress if you have a better one to replace it with, because having no mattress at all is even worse. The more powerful and venerable the theory, the more breakdowns that must occur to make scientists skeptical of its value and open to having another theory replace it.

After a theory is dethroned due to a confluence of many events, later historians might point to a single event as starting the decline or providing the tipping point that convinced scientists to abandon the theory. But this is something that happens long after the fact, and is largely a rewriting of history.

So I do not think that finding one fossil out of place will dethrone Darwin. And ID does not meet the necessary criteria for being a viable alternative anyway, since it appeals to an unavoidable inscrutability as a factor in its explanatory structure, and that is an immediate disqualification for any scientific theory.

A commenter to a previous posting raised an interesting perspective that requires a fresh posting, because it reflects a commonly held view about how the validity of scientific theories get established.

The commenter says:

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“A scientist cannot be certain about a theory until that theory has truly been tested, and thus far, I am unaware of our having observed the evolution of one species from another species. Perhaps, in time, we will observe this, at which point the theory will have been verified. But until then, Evolution is merely a theory and a model.

While we may have the opportunity to test Evolution as time passes, it is very highly doubtful that we will ever be able to test any of the various theories for the origins of the Universe.�
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I would like to address just two points: What does it mean to “test� a theory? And can scientists ever “verify� a theory and “be certain� about it?
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In an earlier posting, the question was posed as to whether it was intellectually consistent to reject the findings of an entire modern scientific discipline (like biology) or of a major theoretical structure (like the theory of evolution) while accepting all the other theories of science.

The short answer is no. Why this is so can be seen by examining closely the most minimal of creationist theories, the one that goes under the label of ‘intelligent design’ or ID.

ID supporters take great pains to claim that theirs is a scientific theory that has nothing to do with religion or God, and hence belongs in the school science curriculum. (This particular question whether ID can be considered a part of science or of religion will be revisited in a later posting. This is becoming a longer series than I anticipated…)

ID advocates say that there are five specific biochemical systems and processes (bacterial flagella and cilia, blood clotting, protein transport within a cell, the immune system, and metabolic pathways) whose existence and/or workings cannot be explained by evolutionary theory and that hence one has to postulate that such phenomena are evidence of design and of the existence of a designer.

The substance of their arguments is: “You can claim all the other results for evolutionary theory. What would be the harm in allowing these five small systems to have an alternative explanation?�

Leaving aside the many other arguments that can be raised against this position (including those from biologists that these five systems are hardly intractable problems for evolutionary theory), I want to focus on just one feature of the argument. Is it possible to accept that just these five processes were created by a ‘designer,’ while retaining a belief in all the other theories of science?

No you cannot. If some undetectable agent had intervened to create the cilia (say), then in that single act at a microscopic level, you have violated fundamental laws of physics such as the law of conservation of energy, the law of conservation of momentum, and (possibly) the law of conservation of angular momentum. These laws are the bedrock of science and to abandon them is to abandon some of the most fundamental elements of modern science.

So rejecting a seemingly small element of evolutionary theory triggers a catastrophe in a seemingly far-removed area of science, a kind of chaotic ‘butterfly effect’ for scientific theories.

Scientific theories are so interconnected that some philosophers of science have taken this to the extreme (as philosophers are wont to do) and argued that we can only think of one big scientific theory that encompasses everything. It is this entire system (and not any single part of it) that should be compared with nature.

Pierre Duhem in his The Aim and Structure of Physical Theory (1906) articulated this position when he declared that: “The only experimental check on a physical theory which is not illogical consists in comparing the entire system of the physical theory with the whole group of experimental laws, and in judging whether the latter is represented by the former in a satisfactory manner.� (emphasis in original)

Of course, in practical terms, we don’t do that. Each scientific subfield proceeds along its own path. And we know that there have been revolutions in one area of science that have left other areas seemingly undisturbed. But this interconnectedness is a reality and explains why scientific theories are so resistant to change. Scientists realize that changing one portion requires, at the very least, making some accommodations in theories that are connected to it, and it is this process of adjustments that takes time and effort and prevents trivial events from triggering changes.

This is why it usually requires a major crisis in an existing theory for scientists to even consider replacing it with a new one. The five cases raised by ID advocates do not come close to creating that kind of crisis. They are like flies in the path of a lumbering evolutionary theory elephant, minor irritants that can be ignored or swatted away easily.

Extra note:

For those of you interested in this topic, the Cleveland Museum of Natural History is having an all day symposium on “Teaching Evolution and the Diversity of Life� on Saturday February 12. I am one of the speakers, speaking on the topic “Science and Intelligent Design� in classroom C from 9:45-10:45. Unfortunately the symposium is not free except for the 4:30 pm talk by Dr. Brian Alters.

The Plain Dealer ran a news item about the symposium and related topics in the Metro section yesterday (Thursday, February 10, 2005).

In an earlier posting, I noted that the US population is roughly evenly split on whether or not to accept the basic tenet of evolution on the origin of humans. What is interesting is that the people who reject evolution feel quite free to do so. They seem to feel that there is no price to be paid.

This is because science is taught pretty much as a set of end results and disconnected facts: The universe is over ten billion years old. The Earth revolves around the Sun. Atoms are made from protons, neutrons, and electrons. Trees take in carbon dioxide and release oxygen. Our genetic information is encoded in our DNA.
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First the bad (and somewhat old) news. In a 2001 survey, the National Science Foundation found that only 53 percent of Americans agreed with the statement “human beings, as we know them, developed from earlier species of animals.�

It is hard to believe that there could be any good news behind this mind-boggling statistic that implies that up to 47 percent of Americans are unwilling to accept a fundamental tenet of evolution and believe that human beings appeared by a special act of creation about 10,000 years ago.

But there is a nugget of good news to be found, since this is the first time that even a simple majority of Americans had accepted that statement.

But even that small glimmer of hope is buried under more bad news. Even though a majority has come around to the accepted scientific view of the origin of humans, the US still lags far behind other countries. In a New York Times article on February 1, 2005, Dr. Joe Miller, director of the Center for Biomedical Communications at Northwestern University is quoted as saying that in other industrialized countries, 80 percent or more typically accept evolution, while most of the others say they are not sure and very few people reject the idea outright.

He goes on to say that in socially conservative, predominantly Catholic countries like Poland, perhaps 75 percent of people surveyed accept evolution, while in Japan it is close to a whopping 96 percent.

So what is different about the US? There are some obvious reasons that can be postulated. One is that the US is in the grip of Biblical literalists who indoctrinate young children with young-Earth ideas and frighten them with the flames of hell if they should deviate from that dogma.

Another is that evolution is either not being taught at all, or is being taught badly so as to be unconvincing, or its teaching is being deliberately undermined (such as using disclaimer stickers in biology textbooks that evolution is “only a theory”, teaching of ‘intelligent design’ as an alternative) by fraudulent claims that it is not a scientifically acceptable theory. The response to these kinds of explanations is to argue for more and better teaching of evolution in schools.

While I am all in favor of better teaching of anything, I am not convinced that inadequate teaching of evolution is the main problem. It may lie in the way the nature of science is taught, and correcting this might require us to pay more close attention to the image we convey of how science itself works and evolves. This may require us to focus, not on more teaching of evolution or any other specific topic, but more generally on the history and philosophy of science.

More about this in a later posting…

Dan had a comment on the “science and proof II” posting that I think is of general interest that requires a fresh posting. He asks:

“Okay, do you have a quick explanation for why falsification is not the distinction between science and religion?

On a day to day level, it works for me. If someone says there exist leprechauns, but they are invisible, and leave no trace in our world, I know that the statement can not be proven wrong so it is not worth arguing against. But if someone says that species evolve from other species, it is conceivable that it could be proven wrong, so it is worth taking seriously. And if enough people try to disprove it and fail, that is good evidence that it might have explanatory power.”

Dan’s point is a good one. At a simple level, falsificationism sounds plausible. The theory that “All swans are white” can be seemingly falsified by the appearance of aa single black swan. Falsification’s appeal stems from the fact that we seem to be able to make a clean distinction between an observation and a theory.

But that distinction becomes blurred when you start looking at the kinds of things that scientists research, because then observations are no longer simple sensory perceptions. The statement “electrons exist” is not a simple observational one but requires us to use a vast array of theories from a range of disciplines in order to interpret the readings of the measuring insruments. So if the “observation” disagrees with the theory being examined, it is not clear where to place the blame. Is it on the theory being tested, or on one of the theories underlying the observations?

So in reality one is always comparing one set of theories with another set of theories and there is no rule that *forces* you to make a particular choice, although good taste and judgment and standard practices may lead the scientific community to a consensus decision.

The other problem with using falsification is that no theory has ever explained everything in its domain. There are always unsolved problems and contradictory results. Trying to reconcile these discrepancies serve as the basis for much research. If we applied the falsification rule strictly, then every theory we have would be falsified.

These are the kinds of things that caused falsificationism to stumble and fall.

Incidentally, even the swan example is not as simple as it looks. Defenders of the white swan theory can retain their belief by arguing that what constitutes a swan is not precisely defined and that the black creature was not really a swan, and other arguments like that. We may dismiss those arguments as silly and self-serving but they are not logically ruled out.

Warning! Shameless plug coming up!

All these issues are discussed in my book “Quest for Truth: Scientific Progress and Religious Beliefs”, published by Phi Delta Kappan Foundation in 2000.

In his comment on my earlier posting on “Science and Proof”, Kurtiss Hare raises an interesting point about the value of religion and what kind of validity criteria I was referring to, so I thought I would elaborate.

When it comes to the *value* of belief structures to an individual, then there are really no external criteria that can be imposed. For example, for someone who has experienced a personal tragedy, a belief in God and a divine purpose for life may be of far more value than all the science in the world.

The point I was trying to muddle through to about science is that it is not being “proven true” that gives scientific theories their credibility, but the fact that they seem to work well, are reliable, and can be used to make predictions.

The probability argument that Kurtiss raises is interesting but has two directions in which it can be taken. The first (which I think is the one he makes) is that the fact that very few planes crash means that the probability of that particular application of the scientific theories (i.e., arriving safely) is high.

But does that translate into a high probability of the underlying scientific theories being true? No, because if you you want to assign a “truth probability” to a scientific theory then you have to compare (for any given theory) the number of predictions that are confirmed to the total number of predictions that are conceivable. Since for any non-trivial theory the number of possible predictions is infinite, the truth probability for *any* theory (however “good”) turns out to be zero!

This seems paradoxical but philosophers of science have not been able to get around it.