I had expected to be as irritated by Michael Behe’s second book as by his first. I had not expected to feel sorry for him. The first — “Darwin’s Black Box” (1996), which purported to make the scientific case for “intelligent design” — was enlivened by a spark of conviction, however misguided. The second is the book of a man who has given up. Trapped along a false path of his own rather unintelligent design, Behe has left himself no escape. Poster boy of creationists everywhere, he has cut himself adrift from the world of real science. And real science, in the shape of his own department of biological sciences at Lehigh University, has publicly disowned him, via a remarkable disclaimer on its Web site: “While we respect Prof. Behe’s right to express his views, they are his alone and are in no way endorsed by the department. It is our collective position that intelligent design has no basis in science, has not been tested experimentally and should not be regarded as scientific.” As the Chicago geneticist Jerry Coyne wrote recently, in a devastating review of Behe’s work in The New Republic, it would be hard to find a precedent.

For a while, Behe built a nice little career on being a maverick. His colleagues might have disowned him, but they didn’t receive flattering invitations to speak all over the country and to write for The New York Times. Behe’s name, and not theirs, crackled triumphantly around the memosphere. But things went wrong, especially at the famous 2005 trial where Judge John E. Jones III immortally summed up as “breathtaking inanity” the effort to introduce intelligent design into the school curriculum in Dover, Pa. After his humiliation in court, Behe — the star witness for the creationist side — might have wished to re-establish his scientific credentials and start over. Unfortunately, he had dug himself in too deep. He had to soldier on. “The Edge of Evolution” is the messy result, and it doesn’t make for attractive reading.

We now hear less about “irreducible complexity,” with good reason. In “Darwin’s Black Box,” Behe simply asserted without justification that particular biological structures (like the bacterial flagellum, the tiny propeller by which bacteria swim) needed all their parts to be in place before they would work, and therefore could not have evolved incrementally. This style of argument remains as unconvincing as when Darwin himself anticipated it. It commits the logical error of arguing by default. Two rival theories, A and B, are set up. Theory A explains loads of facts and is supported by mountains of evidence. Theory B has no supporting evidence, nor is any attempt made to find any. Now a single little fact is discovered, which A allegedly can’t explain. Without even asking whether B can explain it, the default conclusion is fallaciously drawn: B must be correct. Incidentally, further research usually reveals that A can explain the phenomenon after all: thus the biologist Kenneth R. Miller (a believing Christian who testified for the other side in the Dover trial) beautifully showed how the bacterial flagellar motor could evolve via known functional intermediates.

Behe correctly dissects the Darwinian theory into three parts: descent with modification, natural selection and mutation. Descent with modification gives him no problems, nor does natural selection. They are “trivial” and “modest” notions, respectively. Do his creationist fans know that Behe accepts as “trivial” the fact that we are African apes, cousins of monkeys, descended from fish?