(I will be away on travel this week so will be reposting an old series, edited and updated, that discusses the nature of science and the difference between science and religion. New posts start again on Monday, April 21, 2008.)

A few days ago I was working in my backyard when I noticed that the outdoor thermometer that I had fixed to a fence had disappeared. The mountings were still there but had been pulled away slightly. I thought that maybe the wind had blown it off and so I looked at the ground underneath but the thermometer was not there. There is a bed of pachysandra nearby and I looked nearby in it but no luck. I was baffled.

I pondered the various options for explaining the missing thermometer. One was that the wind had been strong enough to rip the thermometer from its mounting and blow it farther away into the pachysandra. The other was that it had fallen to the ground below and had then been taken away by squirrels or the neighbor’s cat. The third was that neighborhood children had borrowed it without permission for some experiment. The fourth was that the International Outdoor Thermometer Cartel (IOTC) had raised the price of these thermometers to such a high value that organized crime gangs were stealing them and selling them on the black market. The fifth option was that aliens had taken it away as a souvenir of their clandestine visit to Earth.

Given these options, I decided that #1 was the most likely one and looked in the pachysandra over a larger area and, sure enough, I found it.

The reason for this anecdote is that it illustrates that I used something that we all use all the time (whether we are consciously aware of it or not), and that is Ockham’s razor to make choices among competing theories.

According to the Encyclopedia Brittanica, the principle behind Ockham’s razor (also called the law of economy or the law of parsimony) was stated by the scholastic William of Ockham (1285–1347), as “Plurality should not be posited without necessity.” The principle is also expressed as “Entities are not to be multiplied beyond necessity.” Ockham did not himself use the word ‘razor’, that was added to his name later by others.

The principle gives precedence to simplicity, but there are two ways it can be used. In the first case (which is more closely aligned with Ockham’s intent), it says that you should not postulate more elements for anything other than the minimum required. For example, in the case of my missing thermometer, if I postulated one theory that a cat had taken it and a competing theory was that a cat that had a striped tail and a scar on its forehead had taken it, then in the absence of any extra information, the former theory is to be preferred. The latter theory just adds elements that do not add any necessary information to the explanation. The application of this version of the principle is fairly straightforward. One seeks the smallest subset of elements of a theory that provides an adequate explanation of whatever you are trying to explain.

The more problematic (but common) use of Ockham’s razor is when you try and apply it to a situation where there are two competing theories that share either no common elements or there exist at least some necessary elements of one theory that the other does not possess. We commonly interpret Ockham’s razor in those situations as requiring us to choose the simpler of the two theories. But simplicity may well lie in the eye of the beholder and it may not be easy to get agreement.

So, for example, in the case of the thermometer that was found some distance away from its mountings, the simpler explanation (for me at least) was that of the wind. If called upon, I could cite Bernoulli’s Principle and the laws of motion to support my preference. That explanation is enough to satisfy me.

But this may not be true for someone else. For someone who is a believer in the existence UFOs and space aliens, a theory that alien vandals landed in my garden, tore the thermometer from its moorings, threw it away in the pachysandra and left in their spaceship, might be the “simpler” explanation. After all, it does not involve the use of calculus.

That is exactly the problem in many of the science and religion discussions. Apart from those people who reject science altogether, the integration of science and religion into one coherent philosophical framework becomes one of the most difficult challenges and there is no simple solution to it. And all of us use Ockham’s razor to resolve it, even though the results are not the same for everyone.

A belief in the existence of god implies that there must be at least some phenomena caused by the intervention of god that lie outside the purview of science. (I am not considering the point of view that god created the world and its laws in one instant of time long ago and then has had a completely hands-off policy since then.)

For example, Biblical literalists will start with the assumption that the Bible is a historical document and that the events described in it (the world was created in six days and is only 6,000 years old, Joshua caused the Sun to stand still, Noah’s flood did occur, etc.) all actually occurred. They will then painstakingly and tortuously try and reinterpret all evidence to be consistent with these axioms. The website Answers in Genesis goes to extraordinary lengths to try and answer questions such as “Where did Cain find his wife?” and “Did dinosaurs live alongside humans?” These are questions that do not trouble anyone who does not treat the Bible as an authoritative source for science and history.

But even those who take the Bible less literally have to confront difficult questions because at some point, the question is going to arise about where you draw the line and ascribe something to the actions of god. Each person will draw the line between god’s actions and the actions of natural laws differently, depending on their personal level of comfort with the explanation.

This is something that believers in any theistic religion have to confront. Some will believe that any event that does not have a ready explanation to hand (a death in the family, an escape from injury, an unexpected recovery from a serious illness) are directly due to god’s intervention to change the course of events. In order to deal with the existence of evil in the presence of an omnipotent and loving god, believers usually end up having to postulate that god’s actions are inscrutable and that we cannot know the answers to at least some of the events that occur in the world.

At the other end, others might believe that god does not actually cause a change in the natural sequence of events but instead exerts his/her influence by working through people. In other words, people are the agents of god’s actions and the sole mechanism by which he/she influences events. So people are cured of illnesses because god inspires researchers and physicians, and so on.

There are also an infinite number of intermediate states between those two extremes. For example, people like the biochemist Michael Behe, who is an intelligent design advocate and author of the book Darwin’s Black Box, accept natural explanations for everything except for a few selected phenomena at the biochemical level (such as the blood clotting mechanism or the creation of the bacterial flagellum) that he feels are unlikely to have been created by natural processes. (See the New Yorker article by H. Allen Orr for a clear description of what Behe’s argument is. Cory also sent me a link to a nice article written by John Rennie, editor of Scientific American, that addresses some of the key points raised by ID advocates.)

Or one can use decide that there is no god (or supernatural entity of any kind), and all that exists is the material world. This is the position of philosophical naturalism or atheism. (I am treating the two terms as effectively synonymous, although professional philosophers might disagree).

So we are left with only Ockham’s razor with which to make a decision but in this case, it is a very personal razor whose use will satisfy only us. I personally find that assuming no god exists makes everything simpler and much more meaningful.

But those who are committed to believing in the existence of god despite the lack of evidence for his/her existence will not agree with me that this is the simplest explanation. They will likely say that having an inscrutable god who for some reason allows unspeakable cruelties is a ‘simpler’ way of understanding the world.

Which position one ends up taking is thus largely determined by deciding which is ‘simpler’ to believe in, which usually means deciding which belief structure you want to believe in and find personally enriching and meaningful, since there is no unambiguous measure of simplicity for incommensurable theories.

(I will be away on travel this week so will be reposting an old series, edited and updated, that discusses the nature of science and the difference between science and religion. New posts start again on Monday, April 21, 2008.)

At its heart, intelligent design creationism (IDC) advocates adopt as their main strategy that of finding phenomena that are not (at least in their eyes) satisfactorily explained by evolutionary theory and arguing that hence natural selection is a failed theory. They say that adding the postulate of an ‘intelligent designer’ (which is clearly a pseudonym for god) as the cause of these so-called unexplained phenomena means that they are no longer unexplained. This, they claim, makes IDC the better ‘explanation’. Some (perhaps for tactical reasons) do not go so far and instead say that it is at least a competing explanation and thus on a par with evolution.
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(I will be away on travel this week so will be reposting an old series, edited and updated, that discusses the nature of science and the difference between science and religion. New posts start again on Monday, April 21, 2008.)
In a previous posting, I pointed out that if one looks studies the history of science, all the theories that have been considered to be science are both (1) naturalistic and (2) predictive. Thus these two things constitute necessary conditions for a theory to be considered science.

This is an important fact to realize when so-called intelligent design creationism (IDC) advocates argue that theirs is a ‘scientific’ theory. If so, the first hurdle IDC must surmount is that it meet both those necessary criteria, if it is to be even eligible to be considered to be science. It has to be emphasized that meeting those conditions is not sufficient for something to be considered science, but the question of sufficiency does not even arise in this case because IDC does not meet either of the two necessary conditions.

I issued this challenge to the IDC proponents when I debated them in Kansas in 2002. I pointed out that nowhere did they provide any kind of mechanism that enabled them to predict anything that anyone could go out and look for. And they still haven’t. At its essence, IDC strategy is to (1) point to a few things that they claim evolutionary theory cannot explain; (2) assert that such phenomena have too low a probability to be explained by any naturalistic theory; and (3) draw the conclusion that those phenomena must have been caused by an ‘unspecified designer’ (with a nudge, nudge, wink, wink to the faithful that this is really god) whose workings are beyond the realm of the natural world explored by science.
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(I will be away on travel this week so will be reposting an old series, edited and updated, that discusses the nature of science and the difference between science and religion. New posts start again on Monday, April 21, 2008.)

Because of my science training and my interest in its history and philosophy I am sometimes called upon to answer the question “what is science?” Most people think that the answer should be fairly straightforward. After all science is such an important and integral part of our lives that everyone feels that they already know what it is and think that the problem of defining science is purely one of finding the right combination of words that captures their intuitive sense.
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Even though I am not a biologist, I find evolution to be an endlessly intriguing subject, constantly throwing up intriguing new facts. Here are some recent items that caught my eye.

Stephen Colbert has a fascinating interview with evolutionary biologist Neil Shubin, discoverer of the fish-land animal transitional fossil Tiktaalik, about how much of our human biology came from fish. In his 2008 book Your Inner Fish: A Journey Into the 3.5 Billion-Year History of the Human Body, Shubin points out that although superficially we may look very different, many of our human features can be found in to have analogous forms in fish and thus probably existed from the time that we shared common fish-like ancestors with them. (Incidentally, Shubin was one of the expert witnesses in the Dover intelligent design trial in which he discussed the theory of evolution and the role that Tiktaalik played in clarifying the link between fish and land animals.)
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(I am taking a break from original posts due to the holidays and because of travel after that. Until I return, here are some old posts, updated and edited, for those who might have missed them the first time around. New posts should appear starting Monday, January 14, 2008.)

Because of my interest in the history and philosophy of science I am sometimes called upon to answer the question “what is science?” Most people think that the answer should be fairly straightforward. This is because science is such an integral part of our lives that everyone feels that they intuitively know what it is and think that the problem of defining science is purely one of finding the right combination of words that captures their intuitive sense.
[Read more…]

(I am taking a break from original posts due to the holidays and because of travel after that. Until I return, here are some old posts, updated and edited, for those who might have missed them the first time around. New posts should appear starting Monday, January 14, 2008.)

The problem of finding definitions for things that clearly specify whether an object belongs in that category or not has long been recognized to be a knotty philosophical problem. Ideally what we would need for a good definition is to have both necessary and sufficient conditions, but it is not easy to do so.

A necessary condition is one that must be met if the object is to be considered even eligible for inclusion in the category. If an object meets this condition, then it is possible that it belongs in the category, but not certain. If it does not meet the condition, then we can definitely say that it does not belong. So necessary conditions for something can only classify objects into “maybe belongs” or “definitely does not belong.”

For example, let us try to define a dog. We might say that a necessary condition for some object to be considered as a possible dog is that it be a mammal. So if we know that something is a mammal, it might be a dog or it might be another kind of mammal, say a cat. But if something is not a mammal, then we know for sure it is not a dog.

A sufficient condition, on the other hand, acts differently. If an object meets the sufficient condition, then it definitely belongs. If it does not meet the sufficient condition, then it may or may not belong. So the sufficient condition can be used to classify things into “definitely belongs” or “maybe belongs.”

So for the dog case, if a dog has papers certified by the American Kennel Association, then we can definitely say it is a dog. But if something does not have such papers it may still be a dog (say a mixed breed) or it may not be a dog (it may be a table).

A satisfactory demarcation criterion would have both necessary and sufficient conditions because only then can we say of any given object that it either definitely belongs or it definitely does not belong. Usually these criteria take the form of a set of individually necessary conditions that, taken together, are sufficient. i.e., Each condition by itself is not sufficient but if all are met they become sufficient.

It is not easy to find such conditions, even for such a seemingly simple category as dogs, and that it the problem. So for the dog, we might try define it by saying that it is a mammal, with four legs, barks, etc. But people who are determined to challenge the criteria could find problems (What exactly defines a mammal? What is the difference between an arm and a leg? What constitutes a bark? Etc. We can end up in an infinite regression of definitions.)

This is why philosophers like to say that we make such identifications (“this is a dog, that is a cat”) based on an intuitive grasp of the idea of “similarity classes,” things that share similarities that may not be rigidly definable. So even a little child can arrive at a pretty good idea of what a dog is without formulating a strict definition, by encountering several dogs and being able to distinguish what separates dog-like qualities from non-dog like qualities. It is not completely fool proof. Once in a while we may come across a strange looking animal, some exotic breed that baffles us. But most times it is clear. We almost never mistake a cat for a dog, even though they share many characteristics, such as being small four-legged mammals with tails that are domestic pets.

Anyway, back to science, a satisfactory demarcation would require that we be able to find both necessary and sufficient criteria that can be used to define science, and use those conditions to separate ideas into science and non-science. Do such criteria exist? To answer that question we need to look at the history of science and see what are the common features that are shared by those bodies of knowledge we confidently call science.

This will be discussed in the next posting.

I have written a lot about the theory of evolution and in the process have quoted short excerpts from various authors, Charles Darwin included. (Please see here for previous posts in this series.)

But in going back and reading the first edition of On the Origin of Species (1859), I am struck by how prescient Darwin was in anticipating the objections that would be raised against his theory and why. He could well have been talking about the situation today, except that then the people who were skeptical and who he was trying to persuade were his scientific colleagues. Nowadays scientists are almost all converts to natural selection (as he predicted might happen) and it is religious lay people who make the same objections he addressed long ago.

To get the full flavor of Darwin’s thinking and his style of writing, here is a somewhat long passage from his conclusions, where he summarizes his case (p. 480-484). The sections in boldface are my own emphasis. (Darwin’s complete works are now available online.)

I have now recapitulated the chief facts and considerations which have thoroughly convinced me that species have changed, and are still slowly changing by the preservation and accumulation of successive slight favourable variations. Why, it may be asked, have all the most eminent living naturalists and geologists rejected this view of the mutability of species? It cannot be asserted that organic beings in a state of nature are subject to no variation; it cannot be proved that the amount of variation in the course of long ages is a limited quantity; no clear distinction has been, or can be, drawn between species and well-marked varieties. It cannot be maintained that species when intercrossed are invariably sterile, and varieties invariably fertile; or that sterility is a special endowment and sign of creation. The belief that species were immutable productions was almost unavoidable as long as the history of the world was thought to be of short duration; and now that we have acquired some idea of the lapse of time, we are too apt to assume, without proof, that the geological record is so perfect that it would have afforded us plain evidence of the mutation of species, if they had undergone mutation.

But the chief cause of our natural unwillingness to admit that one species has given birth to other and distinct species, is that we are always slow in admitting any great change of which we do not see the intermediate steps. The difficulty is the same as that felt by so many geologists, when Lyell first insisted that long lines of inland cliffs had been formed, and great valleys excavated, by the slow action of the coast-waves. The mind cannot possibly grasp the full meaning of the term of a hundred million years; it cannot add up and perceive the full effects of many slight variations, accumulated during an almost infinite number of generations.

Although I am fully convinced of the truth of the views given in this volume under the form of an abstract, I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of facts all viewed, during a long course of years, from a point of view directly opposite to mine. It is so easy to hide our ignorance under such expressions as the “plan of creation,” “unity of design,” &c., and to think that we give an explanation when we only restate a fact. Any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject my theory. A few naturalists, endowed with much flexibility of mind, and who have already begun to doubt on the immutability of species, may be influenced by this volume; but I look with confidence to the future, to young and rising naturalists, who will be able to view both sides of the question with impartiality. Whoever is led to believe that species are mutable will do good service by conscientiously expressing his conviction; for only thus can the load of prejudice by which this subject is overwhelmed be removed.

Several eminent naturalists have of late published their belief that a multitude of reputed species in each genus are not real species; but that other species are real, that is, have been independently created. This seems to me a strange conclusion to arrive at. They admit that a multitude of forms, which till lately they themselves thought were special creations, and which are still thus looked at by the majority of naturalists, and which consequently have every external characteristic feature of true species,—they admit that these have been produced by variation, but they refuse to extend the same view to other and very slightly different forms. Nevertheless they do not pretend that they can define, or even conjecture, which are the created forms of life, and which are those produced by secondary laws. They admit variation as a vera causa in one case, they arbitrarily reject it in another, without assigning any distinction in the two cases. The day will come when this will be given as a curious illustration of the blindness of preconceived opinion. These authors seem no more startled at a miraculous act of creation than at an ordinary birth. But do they really believe that at innumerable periods in the earth’s history certain elemental atoms have been commanded suddenly to flash into living tissues? Do they believe that at each supposed act of creation one individual or many were produced? Were all the infinitely numerous kinds of animals and plants created as eggs or seed, or as full grown? and in the case of mammals, were they created bearing the false marks of nourishment from the mother’s womb? Although naturalists very properly demand a full explanation of every difficulty from those who believe in the mutability of species, on their own side they ignore the whole subject of the first appearance of species in what they consider reverent silence.

It may be asked how far I extend the doctrine of the modification of species. The question is difficult to answer, because the more distinct the forms are which we may consider, by so much the arguments fall away in force. But some arguments of the greatest weight extend very far. . . I believe that animals have descended from at most only four or five progenitors, and plants from an equal or lesser number.

Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from some one prototype. But analogy may be a deceitful guide. Nevertheless all living things have much in common, in their chemical composition, their germinal vesicles, their cellular structure, and their laws of growth and reproduction. We see this even in so trifling a circumstance as that the same poison often similarly affects plants and animals; or that the poison secreted by the gall-fly produces monstrous growths on the wild rose or oak-tree. Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed.

And then the very last, almost poetic, words in the book (p. 490):

There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

Darwin’s achievements are truly magnificent, putting him in the same class as Einstein and Newton, among the greatest scientists of all time.

POST SCRIPT: The Larry Craig incident

Senator Larry Craig (R-Idaho) has taken some strong “family values” and anti-gay stands in the past, despite long standing rumors that he himself was gay. The recent news report that he had pleaded guilty to “lewd” conduct in a public restroom has caused speculation that his career is now over.

It is despicable to harass gays with anti-gay rhetoric and legislation, becoming even worse if those doing so are secretly gay themselves. But Talking Points Memo expresses well my unease with what happened to Craig in the most recent episode. It is not clear from published reports that he did anything that really warranted his arrest and that he was, as Josh Marshall says, essentially caught in a Catch-22 caused by his own risky behavior.

Glenn Greenwald documents the brazen contradictions that right-wingers are indulging in the way they respond to the recent Craig revelation, the reports that surfaced back in 2006 that he was gay, and the recent case of Senator David Vitter (R-Louisiana), another “family values” champion who was found to be a customer of prostitutes.