Refutation of the argument from irreducible complexity

Some advocates of Intelligent Design, notably Michael Behe, argue that the existence of irreducibly complex biological structures poses a critical problem for, or even refutes, evolutionary theory.

There is an obvious hole in this argument. Evolution could produce a structure with redundant parts, and then the redundant parts could evolve away, leaving an irreducibly complex structure. Therefore, in order to show that something could not have evolved, one must show that it is not only irreducibly complex but also unaugmentably complex, i.e., that nothing can be added to the structure without breaking it.

This argument is, of course, not original with me, but I believe the term unaugmentable complexity is my coinage. It has the nice feature of summarizing the entire argument in two words.