Intelligent Design Theory, ( or ID) is a religious argument which attempts to replace the Theory of Evolution. In other words, it attempts to eliminate two of the fundamental evolutionary ideas - that evolution acts through natural selection and unguided evolution.
While a small percentage of ID proponents may acknowledge the religious basis of their belief, the vast majority jump through intellectual hoops to avoid the admission.
In essence, believers in ID maintain that some elements of life have the appearance of having been designed and in this they are obviously correct. Some things do have the appearance of being designed. Where they go wrong is then jumping to conclusion that because things look designed, then they actually were designed.
Stephen J Gould was especially good at pointing out the flaws in nature - a dead give-away that nature was not designed.
Who is the designer?
Strictly speaking, scientists are not dismissing intelligent design, because it has Christian motives. Instead, scientists are dismissing intelligent design based on Popper's demarcation criteria of science.
Intelligent design advocates do not seem to want to answer how and why complexity necessitates an intelligent cause, nor they want to discuss the nature of the designer. However the design inference intelligent design advocates cannot be done without having the knowledge of the nature of the intelligent designer. It is only after we know what kind of intelligent designer it is in order to infer design in some object.
However, explicitly mentioning such cosmic designer will not help the cause of intelligent design. A leading intelligent design think tank, Discovery Institute admits that assertion of a cosmic designer is indeed unfalsifiable. Discovery Institute states: “Of course there's no way to falsify a mere assertion that a cosmic designer exists. This much we are agreed on .” Therefore intelligent design is unfalsifiable if cosmic designer is postulated, and if such cosmic design is not postulated, design inference cannot be carried out. See Flying Spaghetti Monster.
Wedge Strategy and the "Trojan Horse" of Creationism
Intelligent design has been strongly pushed by the Discovery Institute as part of the wedge strategy as outlined in the wedge document in their attempt to create a scientific sounding version of creationism. It has been roundly rejected by most scientists on the grounds that it has no peer-reviewed publications of any standards, and has produced no positive evidence for its claims. The wedge strategy itself is designed to create a public furor over the concept of "teaching the controversy". In the real scientific world, of course, there is no such controversy over the facts and theories underlying modern concepts of evolution.
To date, intelligent design has been introduced into exactly one school district - and there, it tore apart the community, cost the school board millions of dollars, and was eventually thrown out after the Kitzmiller trial. Although intelligent design is always a "Trojan Horse" for creationism - that is to say, creationism with a new name and a few obfuscating principles - there is a sliding scale of how egregious and visible the disguise is. Some people actually believe it to be real science (albeit erroneously), while others use it as a clear pretext for teaching creationism.
In the Kitzmiller case, the disguise was patently obvious. "Intelligent design proponents" there, sought to have the book Of Pandas and People, a creationist's creed, taught as part of a new "intelligent design" curriculum at the local Dover public high school. ID supporters hoped to prove at trial that the book was legitimate science, and not creationism. However, there was one slight problem - the book was a book about creationism, with the words "creator," "creationism," etc., merely replaced with "designer," "intelligent design," etc., by a basic word-processor "find/replace" function, a ruse made obvious by spelling errors (like "cdesign proponentsists") which made the hatchet-job glaringly obvious.
An outstanding issue of Intelligent Design is what mechanism the hypothesised "designer" uses to initiate design diversity. According to the theory of evolution, this mechanism is genetic mutation, resulting from environmental stresses and point mutations caused by the cellular chemical environment. Intelligent Design supporters have yet to offer a plausible mechanism to which diversity can be attributed that differentiates from the mechanisms listed by the theory of evolution. As such the claims by Intelligent Design proponents have yet to offer any empirical evidence to support the claim of a designer.
Is there evidence for or against intelligent design?
First of all, humans aren't durable. They will be crushed at 18 Gs. Their skin is vulnerable to rocks, stones, and when opened it can let bacteria in which can cause severe illnesses. Humans can only survive 3 days without water and 20 days without food.
Humans have other far more obvious problems. Take teeth. Many people have more teeth than mouth giving them horrible problems with wisdom teeth. Eyes, are not particularly good - many people need glasses. Then there is the human back - really bad design and very prone to injury. That's because we are a quadruped which has learned to walk upright but we still don't have all the bits fixed. The appendix, male baldness female breast cancer. The human birth system - what a kludge that is. But hey, it can't be that bad - cause we're made in god's image. Which doesn't say a lot for the blueprint really.
Intelligent design apologists
Proponents of the Intelligent Design hypothesis such as Michael Behe promote theories such as Irreducible complexity as evidence for their ideas. Irreducible Complexity posits that there are certain organs and structures found in nature that have no convincing gradual evolutional pathway, and are too complex to have come about in whole by chance. These ideas are hotly disputed (or dismissed as non-science) by scientists, but regardless of their truth value they do not constitute evidence for an intelligent designer. Proponents of intelligent design make an assumption unwarranted by the evidence in that their logic goes along the lines of "The origins and diversity of the species cannot be accounted for evolution and natural selection alone, therefore there must have been a designer involved."
The very lack of positive, scientific evidence suggesting that there is a designer involved in creating life, begs the question of how the design hypothesis came about. Opponents of the design hypothesis would suggest that proponents are religiously motivated, and that their ideas are not about understanding how life came to exist, but rather about promoting a particular religious world view as espoused in the Wedge Document.
There has also been no attempt to specify the periodicity of the miraculous interventions by the hypothesised "Intelligent Designer". In other words, the philosophy does not state if the miraculous interventions take place annually, monthly, daily or only when the designer feels that miraculous intervention is necessary.
ID proponents have yet to demonstrate that their idea is even remotely scientific by identifying what they believe could falsify it. The Flying Spaghetti Monster ridicules the Intelligent Design movement and shows the impossibility of falsifying Intelligent Design.