Monday, March 07, 2005

Suboptimal Design?

Over on the evolution site, Panda’s Thumb, there is a post entitled Beyond Suboptimality: Logical Fallacy of Behe's "IC means ID" Notion.

This post claims to demonstrate that, even if you accept Behe’s and Dembski’s notion of irreducible complexity (IC), their arguments are inconsistent.

I am not an expert on IC. But to me, it seemed that it was the author of the Panda’s Thumb post, Mark Perakh, who used faulty logic. I present the meat of his argument below, copied from the PT post. If you fear that I selectively cut and pasted, then use the link to read the entire article. Also, use the link to find Perakh’s references.
Perakh wrote:

The essence of Behe’s original IC concept is as follows:
A system is IC if:

(a) It consists of several parts.
(b) The parts are “well matched.” (Behe offered no definition of the notion of being “well-matched.”)
(c) It performs a certain “basic” function (for example, clots blood);
(d) It ceases to function if even a single part is missing.

Having discussed several examples of protein “machines” in biological cells, which, according to Behe, are IC, Behe then asserts that the existence of IC systems in a biological cell points to them being designed rather than having emerged as a result of evolution. I intend to show that Behe’s assertion contradicts logic.

Note that Behe’s concept of IC comprises two components: one is complexity and the other is irreducibility.

...It is evident that for Behe the complexity in question is part of his idea, pointing to design as the alternative to evolution. According to Behe, biological systems must have been designed because they (A) are very complex; and (B) cannot function unless all of their parts are present.

Regarding (A) – complexity – note that Behe has not provided a definition of complexity. Several such definitions have been suggested, though, by Dembski... [A]ccording to Behe and Dembski, the more complex a system, the more likely it was designed – this is the essence of point (A) in Behe’s concept.

Point (B) – irreducibility – in Behe’s concept asserts that an IC system loses its function if even a single part is missing.

According to Behe, protein “machines” in a cell meet both requirements for being IC – they are very complex and they are irreducible.

My goal now is to discuss: what if this assertion is true? Does it lead logically to the design inference? Behe’s answer to this question is “Yes.”

I submit that Behe’s answer is illogical. Here is why.

Start with complexity.

As I have argued before (Perakh 2004), contrary to Dembski’s persistent assertions, complexity is certainly not just disguised improbability. Examples to the contrary abound. Imagine a pile of stones. Each stone has some irregular shape that resulted from a series of chance events. Among these irregularly shaped stones we find a perfectly rectangular brick. It has a simple shape which can be described by a short (i.e. simple) program containing only three numbers – width, length, and height. On the other hand each of the irregularly shaped stones can be described only by a more complex program containing many numbers. However, the probability of a rectangular brick being a result of chance is low: the brick is reasonably (with a high probability) assumed to be a product of design. For irregularly shaped stones the opposite is true – the probability of their origin in chance is larger than in design. Here the relationship between probability and complexity is opposite that prescribed by Dembski’s definition (but compatible with the definition of Kolmogorov complexity – see, for example, Chaitin 2003).

In this example simplicity rather than complexity is a marker of design. I submit that the described example shows not only that Dembski’s definition of complexity fails for certain situations but also that, generally, a more reasonable statement is that simplicity points to design while complexity as such points to chance (more about this in Perakh 2004).

If this is so, then the first part of Behe’s IC concept – complexity - is more reasonably construed as an indication of “blind” evolution rather than of design.

Now turn to the second part of Behe’s IC – irreducibility. Recall that Behe’s idea is that losing a single part of a protein “machine” makes it non-operational. Therefore, says Behe, such a “machine” could not have evolved via a “Darwinian” evolutionary process which requires the existence of functional precursors.

The simple fact is, though, that if an IC system has been designed, we have a case of a bad design. If the loss of a single part destroys the system’s function, such a system is unreliable and therefore, if it is designed, the designer is inept. When engineers design machines, bridges, skyscrapers, TV sets, or artificial kidneys, they always try to envision what can go wrong with their design and how to ensure that small defects do not result in a failure of their product; to this end they build in certain redundancies so that in case some part of the construction fails, its function will not be completely lost but rather taken over by certain self-compensatory features.

IC systems, by definition, are highly vulnerable to accidental damage. IC systems, if they are designed, are poorly designed

…Behe’s concept assumes that the very feature which makes the design bad means the system has been designed. In other words, Behe’s concept means that suboptimality is viewed not as just an unfortunate oversight by the designer; nor is it viewed as something that, albeit seemingly detrimental for the designed entity, has some reasons known only to the designer but unfathomable to us. No, in Behe’s concept the very suboptimality is suggested as a marker of design: an IC system by definition is easily destroyed by damaging just a single part, so a system’s being IC means that its vulnerability is its ineliminable feature. … “The system is suboptimal, therefore it is a product of design” – that is what Behe’s concept entails.

ID advocates are welcome to accuse me of offering a caricature of their idea, but it cannot be helped when a concept’s essence sounds like a caricature or a parody; the idea that “IC implies ID” can most succinctly be rendered by a maxim: stupid, therefore designed.

If this is a satisfying logic, I don’t know what a lack of logic is.
Remember also that Behe’s design inference is based not on some positive evidence but rather on a negative assertion: IC systems could not have evolved via a “Darwinian” path. Since such a path is impossible, concludes Behe, the only remaining option is design.

…How probable is it that the putative designer deliberately designs his products to be IC if this means the product will be unreliable?

…If Behe infers design just because evolution of protein assemblies via indirect “Darwinian” paths looks improbable to him, design inference also has to be excluded because of the improbability of the putative designer’s deliberately incorporating in the protein assemblies the very features (like IC) which make the design bad.

The above discourse is, to my mind, sufficient to reject the design inference based on the IC concept, as logically untenable.
Mark Perakh, Beyond Suboptimality: Logical Fallacy of Behe's "IC means ID" Notion (all emphasis was Perakh's)

Below I give my reasons for claiming that it is Perakh’s logic that is flawed. I admit to being out of field here, so I welcome comments even if they are just to show me where I missed the boat.

Since I have not studied Behe in detail, I am going to base my comment on what the Perakh states about Behe’s ID and IC. And the gist of my comment is that Perakh does not demonstrate what he claims to demonstrate.

As I understand, according to Perakh, Behe claims complexity and irreducibility (of functionality) are necessary to signal design. Or, if you like, low probability and functionality. The and is crucial. As is the fact that, nowhere in this definition, is extreme, inexplicable simplicity precluded from signaling design.

So Behe’s definition does not mean a perfectly rectangular stone, because of its simplicity, does not signal design—it just doesn’t signal the type of design he is investigating, i.e. the design of complex systems. It (the rectangular stone) is a sort of trivial design in the sense that it is beyond dispute—nobody would argue that the 1×4×9 monolith in 2001: A Space Odyssey would occur naturally.

To compare a perfectly rectangular stone to a garden variety stone, obviously of a more complex shape, and which all would agree is more likely to be naturally occurring, and to say that this has anything to do with Behe’s arguments, is wrong in at least two ways:
  1. Behe does not say that simplicity cannot signal design
  2. Behe does not say that non-functional complexity (the natural stone) is a signal of design

Perakh’s conclusion that “simplicity points to design while complexity as such points to chance” is sensible (if the complexity is not functional), but it does not refute Behe, as I understand him (which may be flawed) who (a) (I speculate) would not deny that extreme, inexplicable simplicity (a perfectly rectangular stone) points to design and (b) would not argue that complexity per se points to design, but only functional and irreducible complexity.

The second part of Perakh’s argument is, if I understand it, that if we accept the irreducibility of certain systems then the designer is inept because the very feature that Behe touts (remove one part and it no longer functions) is the mark of an inept designer. He compares Behe's intelligent designs (bacterial flagella) to human designs that incorporate fault tolerance.

I would argue that this is both empirically wrong and philosophically suspect. Here I will only address the former. For the empirical aspect, I will go out on a limb, being a physicist not a biologist. I am guessing that the observed defect rate or failure rate for bacterial flagella is far less that for, say, automobiles. That is, their lack of redundancy is a virtue not a vice; it reflects the fact that the designer in this case did not need redundant systems because the primary systems fail at such a low rate. (Is it not also true that biological systems are self-repairing, a feature that mitigates the need for expensive—from an energy budget viewpoint—redundancies?)

In short, a lack of fault tolerance could, as Perakh suggests, point to a poor design. But, on the other hand, it could signal a superior design. And unless the microbial highways are crowded with stalled bacteria whose flagella have broken down, I would say the case can be made that that system is an example of the latter.

Are bacterial flagella actually unreliable? Do experiments demonstrate that they fail at a high rate? That would seem to be a crucial necessity of Perakh’s argument. Perakh has not demonstrated that the design is suboptimal, and cannot without a detailed cost-benefit analysis of the "missing" redundant systems.

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