(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.

Thus they postulate a non-natural cause for those phenomena and cannot predict any thing that any person could go and look for. (This is not surprising. The designer is, for all intents and purposes, a synonym for god and it would be a bit bizarre to our traditional concept of god to think that his/her actions should be as predictable as that of blocks sliding down inclined planes.) When I asked one of the IDC stalwarts (Jonathan Wells) during my visit to Hillsdale College for an IDC prediction, the best he could come up with was that there would be more unexplained phenomena in the future or words to that effect.

But that is hardly what is meant by a scientific prediction. I can make that same kind of vague prediction about any theory, even a commonly accepted scientific one, since no theory ever explains everything. A truly scientific prediction takes the more concrete form: “The theory Z encompassing this range of phenomena predicts that if conditions X are met, then we should see result Y.”

IDC advocates know that their model comes nowhere close to meeting this basic condition of science. So they have adopted the strategy of: (1) challenging the naturalism and predictive conditions, arguing that these are not necessary conditions for science and that they have been adopted to specifically and unfairly exclude IDC from science; and (2) tried to create a new definition of science so that IDC can be included. This takes the form of arguing that a scientific theory is one that ‘explains’ phenomena.

(There are, of course, variations and expansions on these arguments by the various members of the IDC camp but I have tried to reduce it to its skeletal elements. These variations that IDC proponents adopt are designed to blur the issues but are easy to refute. See this cartoon by Tom Tomorrow (thanks to Daniel for the link) and this funny post by Canadian Cynic about the possible consequences of using IDC-type reasoning in other areas of life.)

The rejection by IDC advocates of naturalism and predictivity as necessary conditions for science goes against the history of science. Recall, for example, that in the struggle between the Platonic and Copernican models of the universe, both sides of this debate involved religious believers. But when they tried to explain the motions of the planets, both sides used naturalistic theories. To explain the retrograde motion of Mercury and other seemingly aberrant behavior, they invoked epicycles and the like. They struggled hard to find models that would enable them to predict future motion. They did not invoke god by saying things like “God must be moving the planets backwards on occasion.” Or “This seemingly anomalous motion of Mercury is due to god.” Such an explanation would not have been of any use to them because allowing god into the picture would preclude the making of predictions.

In fact, the telling piece of evidence that ended the dominance of the geocentric model was that the Rudolphine Tables using Kepler’s elliptical orbits and a heliocentric model were far superior to any alternative in predicting planetary motion.

While it may be true that the underlying beliefs that drove people of that time to support the Platonic or Copernican model may have been influenced by their religious outlook, those earlier religious scientists did not seem to invoke god in a piecemeal way, as an explanation for this or that isolated unexplained phenomenon, as is currently done by IDC advocates. Instead they were more concerned with the question of whether the whole structure of the scientific theory was consistent with their understanding of the working of god. In other words, they were debating whether a geocentric model was compatible with their ideas of god’s role in the world. They seemed to feel that detailed motions of specific planets, however problematic, were too trivial for them to invoke god as an explanation, although they would probably not have excluded the possibility that god was capable of routinely adjusting the motion of planets.

It may also well be true that some scientists of that time thought that god might be responsible for such things but such speculations were not part of the scientific debate. For example, Newton himself is supposed to have believed that the stability of the solar system (which was an unexplained problem in his day and remained unsolved for about 200 years) was due to god periodically intervening to restore the initial conditions. But these ideas were never part of the scientific consensus. And we can see why. If scientists had said that the stability was due to god and closed down that avenue of research, then scientists would never have solved this important problem by naturalistic means and thus advanced the cause of science. This is why scientists, as a community, never accept non-natural explanations for any phenomena, even though individual scientists may entertain such ideas.

So the attempts by IDC advocates to redefine science to leave out methodological naturalism and predictivity fly completely in the face of the history of science. But worse than that, such a move would result in undermining the very methods that have made science so successful.

In the next posting, I will discuss why just looking for ‘good’ explanations of scientific phenomena (the definition of science advocated by the IDC people) is not, by itself, a useful exercise for science.