8/2/2019 The Argument for Intelligent Design From Irreducible Complexity

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The argument for intelligent design from irreducible complexity

In The Origin of Species Darwin said:

If it could be demonstrated that any complex organ existed, which could not possibly

have been formed by numerous, successive, slight modifications, my theory would

absolutely break down. But I can find no such case.

Michael Behe in his book Darwin’s Black Box the Biochemical Challenge to

Evolution argues that some biochemical processes that make up cells and

therefore the basis for life could not have evolved because they are irreducibly

complex. Irreducibly complex means that if any of the parts were removed the

whole wouldn’t work. Behe gives the example of a mousetrap which requires a

spring, bar, hammer etc. to work effectively. If any one of these pieces is

removed the mousetrap can’t work. Biologically speaking Behe gives the

example of cilium:

The function of cilium is to be a motorised paddle. In order to achieve this function

microtubules, nexin linkers, and motor proteins all have to be ordered in precise

function. They have to recognise each other intimately, and interact exactly. The

function is not present if any of the components is missing. Furthermore, many more

factors besides those listed are required to make the system useful for a living cell… 

Douglas Theobald (in less detail than below) characterises Behe’s argument as

follows:

1.  Evolution works by adding elements to a thing step by step

2.  A system that, by lacking any part, cannot function is irreducibly

complex

3.  There are many systems that could not function with any part removed

4.  These systems are irreducibly complex5.  Irreducible complexity cannot, by definition, have proceeded step by

step

6.  Therefore evolution has not produced all things

7.  Therefore Darwin’s theory breaks down 

However, Theobald argues, Behe is wrong about how evolution proceeds. It

proceeds by adding a part and making it necessary.

See bridge example.

8/2/2019 The Argument for Intelligent Design From Irreducible Complexity

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The bridge example asks you to imagine three stones in a river that form a

bridge. The bridge is irreducibly complex – if you remove any of the three parts

of the bridge it will not function. Now we put a plank of wood on the three

stones. The bridge still works even if it’s not, at the moment, irreducibly

complex (you can take off the plank and the bridge still works). Now the

middle stone goes sailing away down the river. The bridge still works (the plank

is on the two stones) and is now irreducibly complex (if you take any part of 

the bridge away it won’t work) again. 

Theobald argues that this is how evolution proceeds – by adding a part and

then making it necessary. NOT by adding a necessary part.