Irreducible complexity
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Contents |
See also
Irreducible complexity and the scientific literature -- IC Argument Flowchart -- Definitional Complexity -- Specified Complexity -- Behe -- Dembski -- Cooption
Definitions
Although definitions and usage vary immensely, they boil down to these:
- An irreducibly complex system has multiple required parts.
- An irreducibly complex system is one which natural evolutionary processes cannot produce.
IDists incorrectly argue that #1 and #2 are equivalent. See definitional complexity and tactical ambiguity for more information.
Overview
The notion of irreducible complexity was introduced by Michael Behe in Darwin's Black Box.
"By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning. An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution. (p. 39)"
In Darwin's Black Box, Behe gave several examples of irreducibly complex systems, including the blood clotting system, bacterial flagellum, and the common mousetrap.
Michael Behe claims that an irreducibly complex system cannot evolve through gradual accumulation of parts, and implicitly claims that it cannot evolve at all. From this, he concludes that any irreducibly complex system found in nature must have been designed by an intelligent being.
This argument rests on several faulty assumptions:
- Faulty assumption #1: Evolution can only proceed by adding parts, never by removing them. In fact, evolution can remove parts as easily as add new ones (perhaps more easily, even). If the system functions better without a given part, there will be selective pressure to remove it. Some species of bats, spiders and deep-water fish lack functioning eyes; it costs resources to grow eyes, for little or no benefit. Whales, although once quadrapeds, no longer have functioning hind legs. Humans no longer have decernable tails.
- Faulty assumption #2: Biological systems never change function. However, the components of an irreducibly complex system, individually or together, can serve a purpose other than that performed by the final system. As Kenneth Miller likes to demonstrate, a mousetrap with a missing trigger can be used as a tie clip; if the spring is missing, it can still be used as a key chain; and the base by itself can be used as a paperweight. See cooption and biological traps.
- Faulty assumption #3: Helpful parts cannot become required parts. But most "IC systems", when examined across many organisms, exhibit variability in what parts are required. See Variability in IC systems.
- Faulty Assumption #4: Omniscience. In order to categorically declare that a biological system or process cannot have developed via a step by step evolutionary process, you would need to have complete knowledge. If there is any gap in knowledge, you could only declare that we do not yet have a viable hypothesis to explain how this system or process could have developed via a step by step evolutionary process. A false positive for irreducible complexity occurs whenever a gap in knowledge is filled which provides a viable hypothesis for a previously unknown process of development. e.g. If you were to utilize our scientific understanding from the 1600's to evaluate a wide range of systems or processes, you would have received a positive for irreducible complexity whenever an unknown is encountered. As we now have viable explanations for a multitude of these, it indicates that the original declarations of irreducible complexity were wrong. The extension of this which indicates that this IC system or process is evidence for a designer was also in error. In effect, irreducible complexity is a "Designer of the gaps" argument with the gaps continually being filled with the advancement of knowledge.
In addition, at the atomic and molecular level, the interaction of the building blocks may be thought of more as Complex adaptive systems than bowling balls. Another problem with irreducible complexity, as it is used by IDists, is that the implied intelligent designer would also probably be irreducibly complex.
In addition to its faulty assumptions, there is also a logical problem with the Irreducible Complexity argument for design in its current state. Irreducible Complexity purports to be a scientific method for consistently identifying biological systems which could not have evolved. Should it fail in any one case, it will be shown to be unreliable and all cases where irreducible complexity is used to argue for design would become suspect by extension. Thus, any example where a system identified as irreducibly complex is shown:
- A. to be reducibly complex or
- B. to have evolved
will indicate that irreducible complexity cannot be reliably identified and/or is not an indication of design. Depending on your point of view, the Blood Clotting system has been demonstrated to fit pattern A or B. As a result, no system that has been identified as Irreducibly Complex should be viewed as a product of design until a more accurate and testable definition of Irreducible Complexity has been proposed.
Furthermore, there are the problems of IC's inability to (scientifically) predict anything, and that it is, ultimately, unfalsifiable.
Examples
See Irreducible complexity and the scientific literature.
Counterexample
A natural bridge is a system which is no longer functional if any of its parts were removed. If such systems could not evolve in a natural process, we had to conclude, that there is a designer of natural bridges. But we know how natural bridges were formed, softer rock has been washed out from under harder rock. The predecessors did not have the same functionality.
Though the evolution of organisms is different from the processes shaping natural bridges, this counterexample shows that natural processes are perfectly capable of producing so-called "irreducible complexity" and there are in fact "clocks without clockmakers", or rather bridges without bridgebuilders.
