But that definition of ID is simply incomplete. ID is at its essence an attempt to falsify the theory of evolution, not a replacement theory of the origins of life and speciation. You can accept ID as a challenge to evolution without adopting a supernatural replacement theory. However, the scientific establishment is not exactly eager to accept ID on these terms because it has no naturalistic alternatives to evolution. To understand ID you must first understand that the theory of evolution depends on two key elements: Genetic mutation and the process of natural selection. Genetic mutations are the randomizing change element. Take them away and you have an endlessly repeating, static gene pool. Natural selection pushes random change in the direction of recognizable speciation. It does this by encouraging the replication of genetic mutations that provide organisms an adaptive advantage. Remove natural selection and the gene pool would seem to churn randomly with no discernable, sustained direction. Intelligent design simply identifies specific biological structures (or processes) for which natural selection could not have provided directional impetus because a) those structures require multiple evolutionary steps to exist; and b) none of the intermediate steps in the evolution of the structure could have provided an adaptive advantage. A key concept in understanding ID is "irreducible complexity". Something is irreducibly complex if it requires all of its parts to be useful at all. The most common non-biological example is the traditional, spring-loaded mousetrap. If you remove any element of the trap it becomes a pile of useless parts, not a less-effective mousetrap and not particularly useful for other purposes. Common examples of irreducibly complex biological structures include the bacterial flagellum and blood coagulation. Remove natural selection as an influence in the formation of an irreducibly complex biological structure and you're arguing that several completely random genetic mutations either occurred at the same time in the same organism or persisted in the same part of the gene pool for millions of years until they were all present to provide an adaptive advantage. The probability of these sequences of mutations occurring completely randomly is effectively zero. The name "intelligent design" derives from the claim that it takes a designer to account for the formation of these irreducibly complex structures. But whether you take that step or not the challenge of irreducible complexity to evolution must be answered. Krauthammer says ID is not scientific because it's not disprovable, or falsifiable. Using his definition of ID that may be true. But in truth there are at least two ways to rebut ID:
a self-enclosed, tautological "theory" whose only holding is that when there are gaps in some area of scientific knowledge -- in this case, evolution -- they are to be filled by God. It is a "theory" that admits that evolution and natural selection explain such things as the development of drug resistance in bacteria and other such evolutionary changes within species but also says that every once in a while God steps into this world of constant and accumulating change and says, "I think I'll make me a lemur today."
- Demonstrate that structures claimed to be irreducibly complex are not, that the individual component parts are adaptively useful in some way
- Propose a plausible alternative mechanism for their formation that doesn't depend either on outside intervention or natural selection