Tuesday, October 17, 2006

The definition of “Irreducibly complex.”

Definition 1. (From Darwin's Black Box)
A single system which is composed of several interacting parts that contribute to the basic function, and where the removal of any one of the parts causes the system to effectively cease functioning

Definition 2. (Behe's "pathway definition")
An irreducibly complex evolutionary pathway is one that contains one or more unselected steps (that is, one or more necessary-but-unselected mutations). The degree of irreducible complexity is the number of unselected steps in the pathway.

Definition 3. (Dembski's definition)
A system performing a given basic function is irreducibly complex if it includes a set of well-matched, mutually interacting, nonarbitrarily individuated parts such that each part in the set is indispensable to maintaining the system's basic, and therefore original, function. The set of these indispensable parts is known as the irreducible core of the system.

I had put my definition here.

25 Comments:

Anonymous Hrafn said...

These four definitions appear to be only roughly equivalent, which is problematic.

Do any of these definitions come with any significant substantiation on why their flavour of IC would be unevolvable, or do they merely assert this claim?

"Definition 2" seems particularly weak from this viewpoint as:
1) "unselected" appears to be too broad a prohibition (as it would exclude neutral mutations, which could easily survive in the population) - "selected against" would be a more appropriate prohibition.
2) Lacking detailed information on the historical environments and competitive pressures, it is impossible to establish which mutations would be positive, neutral or negative, particularly given the possibility of abberant environments and/or pressures.

Additionally, the assertion in "Definition 3" that the "basic" function must be the "original" function appears to be wholly unsubstantiated. I would also point out that inserting assertions into a definition is rather bad form.

3:23 am  
Anonymous Matt Inlay said...

Andrew, here's a question for you. Of the definitions you've provided, which can be empirically determined? In other words, if I showed you a system and asked if it was IC, which of the definitions would allow you to determine whether or not the system was IC?

3:33 am  
Blogger Andrew Rowell said...

Matt,
None of these definitions are quantitative. However there is an understandable and important argument here.

I would be interested to know what you think of my earlier definition.

2:33 pm  
Blogger Andrew Rowell said...

Hrafn,

Do you think that Charles Darwin presented a version of the IC argument as the way in which random change plus natural selection as the universal cause for all biological complexity could be falsified.

"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 out no such case.”

2:39 pm  
Anonymous Hrafn said...

"Do you think that Charles Darwin presented a version of the IC argument as the way in which random change plus natural selection as the universal cause for all biological complexity could be falsified."

Possibly, but in order to demonstrate "that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications," I believe that you would need strong evidence in order to prove this impossibility (e.g. that it unambiguously violated some widely-accepted law of nature). An 'Argument from Personal Incredulity' from somebody inexpert in the organs/systems under contention, let alone the evolution of them (as Behe clearly is), is clearly grossly insufficient.

I would also point out that the research since Darwin's time into evolutionary algorithms has proven them to be far more robust than Darwin (in all likelihood) imagined, making it far more difficult than he would have imagined to prove the evolution of a complex organ to be impossible. In fact, scientific research has continually demonstrated that the more complex something is, the more likely it is to have evolved naturally.

"None of these definitions are quantitative."

Irrelevant, Andrew. The "empirical determination" that Matt was asking for is clearly qualitative not quantitative.

I would also point out that you have failed to address any of the points that I made in my first post.

4:23 am  
Blogger Andrew Rowell said...

Hrafn,

I make no commitment at all to answer all the points raised by commenters. I respond if I have time and if I am interested and if I feel it is important. Having said that I do appreciate your comments and I do read them all and you often make excellent points.

11:36 am  
Anonymous Hrafn said...

Andrew:

Then I presume you are happy for my assessment that these definitions are flawed, and provide no indication whether these systems are evolvable or not, to stand?

3:43 am  
Blogger Andrew Rowell said...

Hrafn,

I agree that at present I have seen no satisfactory and watertight calculations showing that a particular object (e.g the rotary motor) is unevolable.

However this does not mean that such calculations cannot ever be made.

Likewise I have seen no satisfactory and watertight calculations showing that it is evolvable.

At present we have to choose between evolutionist just so stories with a large number of hypothetical intermediates and an intelligent design inference.

As far as I am aware the best pathway that the evolutionists have come up with is that produced by Nick Matzke (here) it is a "just so" story with a biochemical gloss.

It is an attempt to fill in the huge gap between a rotary engine and anything else with imaginary intermediates with limited homology without seriously wrestling with the difficulties along the way.

Are we bound to believe the evolutionists until we demonstrate that this machine is unevolvable? Or can we be permitted a provisional design inference until it is demonstrated that such and inference is unreasonable? I have seen no such demonstration.

3:11 pm  
Blogger Andrew Rowell said...

Hrafn,

If it were possible to find the most difficult single step in the evolution of the flagellum and calculate its probability. Would there be any figure coming out as a result which would convince you that this step could not have occured without intelligent intervention?

3:22 pm  
Anonymous Hrafn said...

"However this does not mean that such calculations cannot ever be made."

Not only have no calculations been made, no framework for these calculations has been proposed. In fact, there has not even been a clear concept of what it is that should be calculated (or how it relates to IC). This leaves IC precisely nowhere.

"At present we have to choose between evolutionist just so stories with a large number of hypothetical intermediates..."

Even assuming that Matzke's analysis is a "just so story," a "just so story" is sufficient to disprove an IC claim of impossibility of evolution (as such a disproof only requires a possible pathway, not identification of the pathway that actually occurred). Further, a "just so story" is clearly superior to no story at all (and as ID presents no nothing about the who/how/why of the design, it tells no story).

"...and an intelligent design inference."

The problem is that there is no "intelligent design inference," merely an unsubstantiated assertion that the flagellum was designed.

"Are we bound to believe the evolutionists until we demonstrate that this machine is unevolvable?"

Yes. The IC argument against evolution is an assertion that certain systems are unevolvable. Until you demonstrate that this assertion is true, it has no more credibility than any other assertion plucked out of thin air.

"Or can we be permitted a provisional design inference until it is demonstrated that such and inference is unreasonable?"

Numerous rigorous demonstrations of the unreasonableness of "design inferences" have been made by the scientific community. IDers simply don't choose to accept them.

5:29 pm  
Anonymous Hrafn said...

"If it were possible to find the most difficult single step in the evolution of the flagellum and calculate its probability."

I would assert that this probability is incalculable.

First, you would need to map out every possible evolutionary path for the evolution of the flagellum (as different paths are likely to have a different "most difficult single steps").

Then you would have to calculate the probability of the necessary mutation occurring.

Then you would have to calculate the probability of this mutation being selected. The trouble is that this calculation would depend on the specific selection pressures, and thus the specific environment that the bacteria existed in, and bacteria can exist in a wide variety of environments. Further, this calculation would require knowledge of the number of bacteria, just short of this single step, that have ever existed in each environment.

Even beyond the near-infinite computationally complexity of this calculation, far too many crucial variables are unknown.

Problems like this is why such calculations are never employed by evolutionary science, but only by anti-evolution pseudoscience.

"Would there be any figure coming out as a result which would convince you that this step could not have occured without intelligent intervention?"

This raises the question of, even if this calculation were possible, would it be meaningful?

Let us assume for the sake of argument that the calculation was possible, and further that the probability was 0.1% (one in one thousand). What would this prove? If you take a large enough group of one in one thousand events, one of them is bound to occur. While the probability of a bacteria developing an outboard motor may be low, the probability of it developing some weird bacterial propulsion system (flagellum, a different form of outboard motor, a rowboat-system, a hydrojet system, etc) will be considerably higher.

Therefore you'd have calculate the probabilities of all these possibilities. Near-infinite computational complexity squared, plus a near infinite number of crucial unknowns.

5:57 pm  
Blogger Andrew Rowell said...

Hrafn,
You said:
'a "just so story" is sufficient to disprove an IC claim of impossibility of evolution (as such a disproof only requires a possible pathway, not identification of the pathway that actually occurred). Further, a "just so story" is clearly superior to no story at all (and as ID presents no nothing about the who/how/why of the design, it tells no story).'

1. A "just so story" does not present a "possible pathway" This is what the whole argument is about. How do we distinguish between a possible and an impossible pathway?

2. You assume that a "design inference" is "no story at all" That indicates your philosophical opinion.

6:34 pm  
Blogger Andrew Rowell said...

Evolution has to be the winner by the way the argument is set up.

The evolutionary just so story must be accepted without a demonstration to be true. The design inference must be rejected until it has been demonstrated to be true.

6:40 pm  
Anonymous Hrafn said...

"How do we distinguish between a possible and an impossible pathway?"

You develop the hypothesis of the pathway to a level of detail that it makes testable predictions. You test these predictions. If the predictions are validated the pathway remains possible, if the predictions are invalidated the pathway becomes impossible and you look for a new pathway to test.

"You assume that a "design inference" is "no story at all" That indicates your philosophical opinion."

No Andrew, it is a statement of simple fact. The design inference contains no story - no series of mechanisms, no information about who/how/why, no contents to the story at all. "In the beginning, something happened (but we won't tell you what), the end." IDers steadfastly (and often proudly) refuse to provide a story.

The design inference only purports to say what didn't happen (i.e. evolution by natural mechanisms), not what did. As such, it cannot contain a story.

6:55 pm  
Anonymous Hrafn said...

"Evolution has to be the winner by the way the argument is set up."

And so it should be. If it were otherwise, if somebody were to have asserted several centuries ago that it was (and would always be) impossible for man to fly, then we would have had to accept this assertion.

This is a well-known logical fallacy (I can't remember its name off hand) - as lack of proof of possibility does not imply proof of impossibility.

7:07 pm  
Blogger Andrew Rowell said...

Evolution is immune from a demonstration that can show it to be wrong:
"I would assert that this probability is incalculable."

Evolution insists that design reaches a standard of evidence that it itself disdains.

7:08 pm  
Anonymous Hrafn said...

"Evolution insists that design reaches a standard of evidence that it itself disdains."

No Andrew, what evolution disdains are:

1) Simplistic attempts purporting to calculate the incalculable.

2) Assertions of impossibility based on no more than Arguments from Personal Incredulity.

2:27 am  
Anonymous Matt Inlay said...

By Andrew: "Matt,
None of these definitions are quantitative. However there is an understandable and important argument here.
"

Andrew, if you cannot determine empirically whether or not a given system is IC, then what use is it to say that IC systems cannot evolve? This is an important distinction that non-scientists often have a difficult time trying to grasp. Definition 1 can be used to determine if a system is IC. All you have to do is take an existing system, knock-out a gene whose product is a component in that system, and then measure for functionality. Definition 2 is entirely useless. Such IC systems cannot evolve by definition. There are zero systems in biology that fall under definition 2. To try to apply definition 2 to the flagellum or the immune system is a classic bait-and-switch.

As for definition 3, it makes a critical error. It assumes that the function of extant system is its original function. That is a totally ludicrous assumption to anyone that studies biochemistry. There is no way to know what the original function of a system is.

The only definition of IC that can be used to identify IC systems is simply a multi-part system where more than one of those parts is essential for that system's function. However, systems that meet that definition are completely evolvable, because such a definition of IC does not take into account co-option.

As for your definition:

"By irreducibly complex I mean that the production of a particular function (in this case selectively advantageous propulsion by a rotating propellor of some kind) requires many specific simultaneous changes in 2 or more proteins such that it is unreasonable to think of them happening by chance."

This definition is scientifically useless because you cannot identify a single system that meets such criteria.

By Andrew: "The evolutionary just so story must be accepted without a demonstration to be true. The design inference must be rejected until it has been demonstrated to be true."

This is a distorted description of the two sides. The evolutionary model for the origin of the flagellum makes predictions and provides details that can be tested in the lab. The design inference makes no positive predictions, and provides no details that can actually be tested. As a result, an evolutionary model has the potential to be better refined and to have more evidence favoring it discovered. For the reasons I mention above, a design inference has no such potential. Unless of course it makes explicit assumptions about the designer and its methods, which IDists adamantly refuse to do.

One thing I want to point out when we discuss complex systems. If IC systems truly cannot evolve, then a 50 part IC system has the same level of evolvability as a 3 part IC system (that is, none at all). If IDists were convinced of the unevolvability of IC systems, then these conversations should be focused on the simplest IC systems available, not the most complex. That is an inherent weakness in the IC argument, that it's proponents hide behind the most complex systems they can find.

I know a counter to this argument is to bring up an example like Mount Rushmore. Cleary Mount Rushmore is designed, but there are simpler structures that resemble human faces that appeared naturally. I can imagine an IDist countering my logic by saying that I'm trying to show that because a simple face-like rock formation can occur naturally, I'm arguing that Mount Rushmore could have appeared naturally. This would be a total distortion of my argument, for the simple fact that there are numerous qualitative differences between a simple face resembling rock formation and Mount Rushmore (I'll leave it to you to name some of them). Are there qualitative differences between a 50 part IC system and a 3 part? If you agree that a 3 part IC system could have evolved, then you must also concede that a 50 part could have evolved, unless there's some kind of qualitative difference between the two systems.

10:51 pm  
Blogger Andrew Rowell said...

Matt,

Thank you for your response. Sorry to be so slow responding.

You said with regard to my definition:
them happening by chance."

This definition is scientifically useless because you cannot identify a single system that meets such criteria.

Do you mean to say that biochemistry can never identify a single system that meets these criteria? If so what evidence do you have for this certainty?

2:24 pm  
Anonymous Matt Inlay said...

Hi Andrew, thanks for responding.

Here's your definition of IC:
"By irreducibly complex I mean that the production of a particular function (in this case selectively advantageous propulsion by a rotating propellor of some kind) requires many specific simultaneous changes in 2 or more proteins such that it is unreasonable to think of them happening by chance."
(boldface mine)

To which I wrote:
"This definition is scientifically useless because you cannot identify a single system that meets such criteria."

And you responded:
"Do you mean to say that biochemistry can never identify a single system that meets these criteria? If so what evidence do you have for this certainty?

The issue here is that you're defining an IC system by its history. How can we identify whether a system required multiple simultaneous changes in its origination? We cannot, unless we already know the pathway that it used to originate. For example, for many 3 part IC systems (I'm using Behe's original definition of IC, btw), we can hypothesize an evolutionary origin that does not require multiple simultaneous changes. In other words, each of the changes that we propose occurred happened sequentially, one step at a time. This is completely "legal" by the current standards of Darwinian evolution, as defined by IDists. Now how does this apply to larger systems like the bacterial flagellum? Unless you know the pathway by which the flagellum originated, you cannot say that any step required multiple simultaneous changes. And unless you can say that it did, you cannot label this system as IC, according to your definition.

If you think there are any systems out there that meet your criteria, then by all means say so, and provide the evidence that they do.

So to answer your question specifically: "Do you mean to say that biochemistry can never identify a single system that meets these criteria? "

Only in systems where the origin is already known. And in any biological system whose origin is already known, none meet that criteria.

7:58 pm  
Blogger Andrew Rowell said...

Matt,

Are you saying then that it is impossible to falsify a co-option/natural selection pathway for the bacterial flagellum?

12:20 pm  
Blogger Andrew Rowell said...

Hrafn,

I said:
"You assume that a "design inference" is "no story at all" That indicates your philosophical opinion."

You said:
No Andrew, it is a statement of simple fact. The design inference contains no story - no series of mechanisms, no information about who/how/why, no contents to the story at all. "In the beginning, something happened (but we won't tell you what), the end." IDers steadfastly (and often proudly) refuse to provide a story.

The design inference only purports to say what didn't happen (i.e. evolution by natural mechanisms), not what did. As such, it cannot contain a story.

A design inference to an unknown human being is allowed presumably and you accept that such an inference is a meaningful cause explanation.

A design inference from outer space is also resumably allowed.... these are presumably NOT just empty explanations signifying nothing?

12:25 pm  
Blogger Andrew Rowell said...

Hrafn,
I said:
"Evolution insists that design reaches a standard of evidence that it itself disdains."

You said:
"No Andrew, what evolution disdains are:
1) Simplistic attempts purporting to calculate the incalculable.
2) Assertions of impossibility based on no more than Arguments from Personal Incredulity. "

Assertions of possibility need to be demonstrated just as assertions of impossibility. Let us see a possible pathway instead of just vague hand waving.

1:04 pm  
Anonymous Hrafn said...

"A design inference to an unknown human being is allowed presumably and you accept that such an inference is a meaningful cause explanation.

A design inference from outer space is also resumably allowed.... these are presumably NOT just empty explanations signifying nothing?"


Even for an "unknown human," we generally know some things about them: e.g. when and/or where they lived, what culture or civilisation they came from, and so on. From this we can develop hypotheses about the means and motives of this "unknown designer." This is the story.

With your unknown, postulated, alien, we don't even know this. We have nothing. We don't even have an unequivocal claim as to what it was they are meant to have designed.

You keep repeating "design inference" as though that magically makes everything all right. To any scientist, it's just an empty rhetorical flourish.

Unless you are prepared to say something substantive about who/what/why/when/where, you have no story, and nothing either of interest to, or testable by, science.

6:54 am  
Anonymous Hrafn said...

"Assertions of possibility need to be demonstrated just as assertions of impossibility. Let us see a possible pathway instead of just vague hand waving."

Vague, meaningless, rhetorical drivel, Andrew.

What possibility am I meant to be demonstrating? What pathways?

If the answer is "all evolution" and "all evolutionary pathways," then I'm afraid you're going to have to wait several centuries.

I would however point out that evolutionary science has already mapped out hundreds (and quite probably thousands) of such pathways already.

That is the big difference between Evolutionary science and ID - evolution progresses (as can be seen from the thousands of research journal articles on the subject), ID merely chases its own tail, in ever decreasing circles (what has Behe said of any substance since Darwin's Black Box? What has Dembski said of any substance since The Design Inference?).

7:07 am  

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