1. (Science and Creationism: A View from the National Academy of Sciences, Second Ed., p. 19, National Academy Press, 1999).

2. Spetner, L. Not by Chance. Judiaica Press, New York 1998. Ch 5.

3. Personal notes from Dr. Michael Behe. My thanks to the Boston Review for publishing my reply to Allen Orr's review of my book. I would like to address the main points of several critics in the symposium who, I believe, have mistaken notions of what I am arguing.

Allen Orr

Professor Orr has a mistaken notion of irreducible complexity. I thought I made that clear in my reply, but from his response I suppose I did not, so let me try again. I define irreducible complexity in Darwin's Black Box as "a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning." Orr, however, uses the term loosely to mean something like "if you remove a part, the organism will die." In his review he talks about lungs, saying "we grew thoroughly terrestrial and lungs, consequently, are no longer luxuries-they are essential." The problem is, if you quickly dissect lungs from an animal, many parts of it will continue to work.

The liver will work for a while, muscles will twitch, cells will metabolize until they run out of oxygen. Thus lungs are not absolutely required for the function of those other parts, not in the way that a spring is absolutely required for a standard mousetrap or nexin linkers are required for ciliary function. That's the problem with using poorly chosen examples, especially at the whole-organ level. I am careful in my book (pp. 46-47) to say that you must look at molecular systems to see if Darwinism can explain their development.

When you look at irreducibly complex molecular examples, it is clear that Darwinism has not and, I believe, cannot explain them. Orr's main line of argument, therefore, simply misses the point.

I should also point out that, contrary to Professor Orr's assertion, we do not know that swim bladders evolved into lungs by natural selection. There is absolutely no evidence for it. It may be likely that lungs are descended from swim bladders, but no experiment has indicated that natural selection can do the trick. In fact, no one even knows at the nuts-and-bolts molecular level what it would take. Orr simply assumes it is possible because he is not bothering with the myriad molecular difficulties that would face such a transformation.

Orr says that the parts of a mousetrap might have started out as something else, and then were changed into their current parts. I address this type of argument on page 66 of Darwin's Black Box. Essentially this approach doesn't help. The parts still have to be adjusted to each other at some stage, and they still don't work until all the parts have been so adjusted. That requires intelligent activity. Orr says we know mousetraps are designed because we have seen them being designed by humans, but we have not seen irreducibly complex biochemical systems being designed, so we can't conclude they were. I discuss this on pp. 196-197.

We apprehend design from the system itself, even if we don't know who the designer is. For example, the SETI project (Search for Extraterrestrial Intelligence) scans space for radio waves that might have been sent by aliens. However, we have never observed aliens sending radio messages; we have never observed aliens at all. Nonetheless, SETI workers are confident, and I agree, that they can detect intelligently-produced phenomena, even if they don't know who produced them. Orr's criterion is also subject to a reductio ad absurdum. Suppose we flew to an alien planet and observed a deserted city. Orr's position would hold that we can't conclude the city was designed, because we have never seen aliens producing cities, and he would oblige us to search for an unintelligent cause for the manifestly designed city.

Orr finds it "extremely curious" that I think some systems could evolve by natural selection, but that others couldn't. I discuss this on pp. 205-208. Simply put, some systems are more complex than others, irreducibly so. If one biochemical system looks pretty much like the other to Orr, then he isn't going to see any problems. However, if you attend to the details of each system, as I tried to do, difficulties for Darwinism loom at many places.