n 1996, the Free Press published a book by Lehigh University biochemist and intelligent design advocate Michael Behe called Darwin's Black Box: The Biochemical Challenge to Evolution. The book's central thesis is that many biological systems are "irreducibly complex" at the molecular level. Behe gives the following definition of irreducible complexity:

By irreducibly complex I mean 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. An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution. (p. 39)

Although the argument from irreducible complexity is essentially a rehash of the famously flawed watchmaker argument advanced by William Paley at the start of the 19th century, Behe's book has attracted a great deal of attention from creationists and non-creationists alike. The articles collected here address the claims made by Behe in his book.

The Mullerian Two-Step: Add a part, make it necessary (or, Why Behe's "Irreducible Complexity" is Silly)

A simple and concise explanation for why the anti-evolutionary argument from "irreducibly complexity" is flawed — gradual evolution by natural selection readily evolves "irreducibly complex" structures.

Darwin's Black Box: Irreducible Complexity or Irreproducible Irreducibility?

Keith Robison reviews Michael Behe's book Darwin's Black Box, which claims that many biological systems are "irreducibly complex" — that in order to evolve, multiple parts would have to arise simultaneously. But is it true?

Publish or Perish: Some Published Works on Biochemical Evolution

This list of papers has been collected in response to Michael Behe's claim that the scientific literature is virtually silent on the topic of molecular evolution.

Behe's Criticism of Evolution in Biochemistry Textbooks

In addition to claiming that the scientific literature devotes no time to questions of molecular evolution, Michael Behe has also said that the same is true of college biochemistry textbooks. Here, the author of some of the textbooks Behe has reviewed demonstrates this claim to be false.

Is the Complement System Irreducibly Complex?

One of the molecular assemblages that Michael Behe claims is "irreducibly complex" is the complement system, an arm of the vertebrate immune system so named because it "complements" the effect of antibodies. This essay outlines the functioning of the complement system and undercuts Behe's argument by showing that simpler yet still functional versions of it exist in nature.

More articles about irreducible complexity and intelligent design can be found at the sister site of The Talk.Origins Achive, Talkdesign.org: Critically Examining the "Intelligent Design" Movement:

Irreducible Complexity Demystified

This FAQ shows that molecular evolution is much too flexible for IC to be an obstacle, shows that Behe's argument is fallacious, and using Venus' flytrap shows that the mousetrap analogy is misleading.

Evolving Immunity A Response to Chapter 6 of Darwin's Black Box

Reviews immune systems of various animals and finds that their complexity is not the intractable problem that Behe would have us believe.

Evolution in (Brownian) Space: A Model For the Origin of the Bacterial Flagellum

Michael Behe, William Dembski, and other intelligent design advocates claim that the bacterial flagellum is too complex to have evolved. This article proposes a possible step-by-step model for the evolution of the flagellum. This article is rather technical and thus has a background file that links to introductory material, articles by intelligent design advocates on the flagellum, and rebuttals to their arguments.

Two documents in this Archive have a subsection addressing Behe's claims about irreducibly complex features:

Applying the Method to Nature: Irreducible Complexity

Discusses how Behe's fellow intelligent design advocate William Dembski uses irreducibly complex arguments in his book No Free Lunch. Part of Not a Free Lunch But a Box of Chocolates.

Suboptimality and Irreducible Complexity

Discusses the implications of suboptimal biological features on Behe's argument. Part of 29+ Evidences for Macroevolution.

The Quote Mine Project examines some of the quotes used by Dr. Behe.

Orr and Coyne unexpectedly find that there is little evidence for the neo-Darwinian view

John McDonald thinks that research on the genetic basis of adaptation has led to a great Darwinian paradox

Behe, Darwin's Black Box, and irreducible complexity are the subject of two winning posts and one runner-up post of the Post of the Month contest of the talk.origins newsgroup which are archived in this web site.

February 1997: Behe and the Blood Clotting Cascade

December 1999: Behe, the Krebs Cycle, and Models of Origins of Complex Biochemical Structures

October 2003 runner-up: Why Behe's Black Box Is Empty

September 2006: Irreducible Complexity as an Evolutionary Prediction

This Archive also has a copy of Behe's testimony at the Kansas Evolution Hearings and his trial testimony at Kitzmiller et al. v. Dover Area School District et al. Short rebuttals to many arguments made by Behe and other intelligent-design advocates can be found at the molecular biology and detecting design sections of an Index to Creationist Claims.