Part 3 of Behe's response to Lehigh Colleagues

From the article:

That seems like a rather fatal flaw in IC. Combining IC with the most recent Behe book this means that IC systems can arise by from non-IC systems through mutations that degrade genes not needed in the IC system. Even with Behe’s definition of how “Darwinian” evolution works, it can easily produce IC systems.


Yes, his own admission seems to strike a serious blow to the IC argument as support for ID.

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IC systems can arrive through natural selection but that is not his argument.

His argument is that IC systems are a powerful challenge for the Darwinian mechanism. If the IC system is simple enough it can arise but not all IC systems are simple.

That is the powerful challenge.

He is stating that IC systems can evolve - which makes the whole point of IC systems related to ID seem moot. Does Behe propose any empirical way to distinguish between IC systems that can or cannot evolve?

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He doesn’t say they cannot evolve as that would be forcing him to prove a negative which is not really empirical science as empirical science is always tentative.

His examples in Darwins black box are the flagellum and the blood clotting system as “powerful challenges”.

How do you objectively determine if an IC system is simple or not simple? Sounds like one more case of ignorance based personal incredulity .

So if Behe admits they can evolve, the “powerful challenge” isn’t quite as powerful anymore. Wouldn’t you agree? And how can you tell which IC arguments pose “powerful challenges” and which ones don’t? Is there a certain number of polypeptides that delineates the two?


The size and number of proteins.

What size and what number, and how were those values objectively determined?

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Not really unless the Darwinian claim is reduce to simpler adaptions. The cell is chock full of irreducibly complex structures that make the flagellar look like a chip shot.

By the number of bits that need to be generated to perform a function. The number of bits is 500 as a limit to what a random search can achieve.

ID-Creationist “Simple IC systems can evolve but non-simple ones can’t”

Scientist: “What prevents simple IC systems from evolving into more complex ones through the same natural processes?”

ID-Creationist: (crickets chirping, wind in the branches…)

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Bill’s avoidance and non-answer to the questions noted. Bill can’t tell us what is a simple vs. a non-simple feature.

Since evolution isn’t a random search why is that relevant?

So you are claiming it is a directed search?

Yes, and Behe has now stated that they can evolve.


No he has not. Not sure how you came up with this :slight_smile: Your a smart guy let’s not play word games.

Irreducible complexity is an argument that has a seat at the table and has identified serious challenges to evolutionary mechanisms.

Alright, I will confess to a bit of putting words in Behe’s mouth, but let’s look further at what he actually wrote. Here is the end portion of the quote from @T_aquaticus, with the sentence that follows:

Irreducible complexity does focus on the current state of a system, but it does not assume that “complex interdependency has always existed.” Rather, it strongly implies (although does not absolutely rule) that the complex interdependency did not arise by Darwinian processes — that it required intelligent input to produce.

Behe grudgingly admits (with his parenthetical expression) that the evidence can only “strongly imply” development of complex IC systems without “Darwinian processes”. This indicates that he does not feel comfortable stating that these complex IC systems cannot evolve. You can see why this is effectively similar to saying that complex IC systems can evolve.


This is simply not setting himself up to have to prove a negative which is prudent for a scientist doing empirical research.

What irreducibly complexity does is stretch the length of a random search before a vehicle (fitness) to fix a set of mutations can happen.

Given what we are observing it is a pretty cleaver idea.

That’s absurd. Stanley Prusiner did everything but prove a negative (prions do not contain genetic material) and won a Nobel Prize.