Intelligent design is a concept authored by pre-Christian philosophers (Plato and Aritotle in 4th Century BCE Greece, and Cicero in First Century BCE Rome). It was Christianized by St.Augustine in the 5th Century AD. Being the most "psychologically friendly" it has had more general appeal that the other early arguments that used the ideas that there must be a First Mover or a First Cause. Voltaire, no intellectual slouch, bought it. But David Hume's criticism of the argument did much to lay it to rest. Even if philosophically valid it would not prove a moral creator or even a creator concerned with the world. Book 4 of the free ebook series "And Gulliver Returns" (http://andgulliverreturns.info) gives the philosophical neophyte a brief survey of the various "proofs" for a creator and some refutations of the arguments.
The argument for intelligent design is often used by Christian fundamentalists with the intent of establishing Creationism as the mainstream doctrine governing the Western view of the natural world, life, and all life processes. According to the wedge strategy developed by The Discovery Institute (theoreticians of intelligent design), intelligent design is meant to be a Trojan horse in the scientific arena, with the ultimate goal of displacing Charles Darwin's scientific theory of evolution which they felt contradicted and ridiculed Creationism.
Intelligent design uses the code words of science without actually using a scientific approach. It tries to treat similarities between doubts at the religious and at the scientific level to put them on the same level. Craftily edited quotes of famous scientists add to the confusion. See: Quote mining. Intelligent design especially advertises the cases of great scientists who claimed to be believers, wihout pointing out the fact that these scientists never biased their scientific approaches with their own faith. Albert Einstein is sometimes described as a believer though he saw God as an impersonal life force.
Who gets to decide what one is to believe? And on what basis? The true scientist says, "Here is my model of the world. It has great practical utility because it enables me to predict what will happen in the real world, so I can avoid doing the things that are not going to produce the results I want and can try to do things that will produce good results. Try my model out and tell me about any places where it may give incorrect predictions." The authoritarian ideologue says, "You must believe this because my religion says so. If that is too much for you, at least consider that my model of the world is plausible." So we get empirical support on one side and fear and plausibility on the other side.
The argumentation used by promoters of intelligent design is often made complex in order to mask the biases and flaws of the logic. Most scientists have a tough time keeping the debate intelligible because intelligent design advocates are interested in converting people to their point of view rather than in rational argument. The Gish gallop is one of many techniques they use to give the false impression that they can win an argument. Intelligent design actually shouldn't be invited to any scientific debate since it is not about science but religious beliefs. It is not grounded in a chain of careful argument from empirical evidence to hypotheses and then to a model or theory that has been amply tested and not found to have major flaws. It is grounded on a tissue of rationalizations stemming from religious belief and the course of its development is to try and prove what its adherents already believed on the basis of their religious faith.
Intelligent Design is the antithesis of science. It was from the beginning designed by Creationists as a science killer. In order to ensure the success of any set of rationalizations such as intelligent design, it is most useful to disable the processes of critical reasoning by which scientists routinely vet even their own theories.
Intelligent design became a key entry point for fundamentalists in their actual ultimate quest: the systematic replacement of Western democracy with Christian theocracy; hence the battle for its promotion in our public schools. After years of guerrilla marketing and intensive lobbying and propaganda in the US (with the benediction of president George W. Bush, who counts Christian fundamentalist among his most ardent supporters), Europe is becoming their new playground.
Hardliner Islamic fundamentalists, who also promote some form of Creationism, are considering an Islamic version of intelligent design. Some Orthodox Jewish clergy, while acknowledging the value of intelligent design principles, recognize that these principles are generally faith-based.
Intelligent design is an account of the existence of complicated entities such as human beings that poses as a scientific theory, when in fact its conclusions rest on a question: "How else could one explain the presence of such intricately fabricated entities?" It does not rest on the careful analysis of evidence to see where the evidence may lead. Instead, it gives a conclusion and then says, "Prove me wrong."
This approach is a form of "data mining," an approach with a flaw that is well known in other fields such as stock picking and terrorist profiling. A familiarity with Bayes' theorem would demonstrate the failure. But here is a nonrigorous account:
Essentially, intelligent design advocates have demonstrated that many developments in evolution are not likely. So the question, seemingly, is a simple betting proposition--is it more likely that the squid's eye was created by a designer or by a chain of thousands, or millions, of historical events, any one of which could have been different? Since none of these events was directly observed, one might well prefer the simpler creationist explanation (but see below, on explaining unobserved creators and their motives).
However, that proposition is a side bet. The main proposition is this: what are the odds that any creator would create THIS squid's eye rather than some other one? The Creator traditionally invoked by Christianity is a being omniscient, omnipotent, omnipresent, and eternal--in other words, a being on whose power there are no limits. That sort of creator would would have at his disposal an INFINITE number of designs for squid eyes. The odds against the existing squid eye developing by random variation may be trillions to one, but the odds against a god creating that eye instead of another are infinite. And infinity is infinitely larger than any quantity of trillions.
The more powerful the designer, the less likely it is that this particular world was designed.
Like Creationism, the story of intelligent design fails to account for the existence and characteristics of the presumed designer of the Universe. Like Creationism, it is a rejection of not just Darwinian Natural Selection, but of the very idea and process of science as an investigation of the natural universe through testing hypotheses against real phenomena leading to the comprehensive explanations that have predictive power that are called theories. By the standards of the creationists, not just biology, but also chemistry, astronomy, physics, and all other branches of science do not meet their standards for knowledge that is proven, complete, and final.
Part of the blame for the success of creationists and believers in intelligent design lies with the mass media (and perhaps some ill-informed teachers, too). Too often something that is little more than a hypothesis or a report on ongoing research is hailed in the mass media as a "revelation" of science. Before long additional research undermines the original tentative conclusion and some new tentative conclusion is announced. People become disillusioned by this apparent switch from "Truth 1" to "Truth 2," not understanding that the progress of science is always by way of casting out what was previously thought to be true when some new evidence comes into the picture, establishing a new "convenient fiction" that encompasses both the old and new knowledge, and then waiting to see where that theory breaks down.
There is also a not very subtle logical fallacy involved with the account called intelligent design. If we had in our possession a machine that was obviously designed to produce noodles, a supply of noodle ingredients, and then we tried out this machine, we would be justified in saying: "If we stoke and operate the Jiffy Noodle Maker, then we will get a pile of uncooked noodles." We could try this experiment as many times as we wanted, at least until we no longer had a functioning Jiffy Noodle Maker machine and the required ingredients, and we could feel justified in saying, "It's a very safe bet that if you fire up the noodle maker you will get some noodles out of it." However, if we walked into somebody's kitchen and found a bowl full of newly made noodles, we would not be justified in arguing, "If we get a pile of uncooked noodles, then somebody has stoked and operated a Jiffy Noodle Maker." That is to say, "Statement A implies Statement B" is not the same as "Statement B implies Statement A." You can't just swap the direction of the arrow of logical implication.
If, millions of years ago, a spaceship came into this solar system and fabricated DNA and other required components to make various forms of life appropriate to the Earth existing at that time, then we would have a case of "Intelligent design." But (1) that is not the only possible explanation for the existence of life on earth (and there are lots of things that would seem extraneous to that explanation -- Why would they have bothered to...?), and (2) somebody would still have to explain where and how these aliens developed.
"Intelligent design" is important to some people because they can use it to bolster belief in the holy scripture that they prefer (it could be the Koran), and that bolstered belief in turn supports a form of social and political organization that they prefer and in which they may well aspire to hold positions of power. Many religions depend on statements about the natural world to support their demand for belief, and the power of science to provide alternative explanations does, in fact, undermine their claim of truth.
In short, belief in an ideology such as intelligent design can work in favor of authoritarians who want power. It takes no more work to defend this theory than it takes to defend the theory that life on earth was seeded by an ancient alien civilization from some place long ago and far away. It is cheap and effective.
The countermeasure most effective against this manipulation is to teach children in schools all over the world how to think scientifically. One does not have to be confrontational to do so. Basic science can involve experiences so universal, and so powerful in the way they convince us of their reality, that anybody who denied those experiences would ridicule himself/herself. Just ask, for instance, "Is the correct balance point for a teeter-totter just a contingent matter somehow? Or is there a constant relationship between weights on the two ends and the lengths of the two lever arms?"