There is a classic debate adage that is highly relevant to many an internet disagreement: When the facts are on your side, pound the facts. When the facts are not on your side, pound the table.
Even one who is relatively new to a subject-matter under discussion can learn much by observing which strategy a debater employs. If one's arguments themselves are clear & rational, it is unnecessary to resort to ad-hominem, name-calling, or extreme comparisons.
Note that appeals to motive are but a specific case of the ad-hominem fallacy. Whether or not a specific hypothesis for the origin & order of life is scientific, rejecting a hypothesis on the basis of proponents' motives, rather than evidence, is decidedly unscientific.
Additionally, if a person believes in some form of intelligent design it no more entails agreeing with everything said by a given intelligent design organization than does believing in some form of Christianity entail agreeing with every pronouncement of every Christian denomination.
The basic argument for design
At its heart, intelligent design is making a claim that is also made in other scientific disciplines:
P1: X is the only known cause of Y
P2: Y is observed
C: X caused it
Any time complex written script is found etched in stone, archeologists posit (correctly) an intelligent agent behind the writing, even if that intelligent agent cannot be directly observed. While wind, erosion, natural cataclysms, etc., can cause scratches in rocks, archeologists recognize that the Rosetta Stone was not produced by natural causes, but by an intelligent agent.
Archeology is using the same abductive argument described above.
The study of archeology would collapse if it were never possible to determine whether an artifact was created by humans or by natural processes. If intelligent design is pseudoscience on the basis of the basic argument outlined above, then archeology relies on much pseudoscience as well.
The OP asked about intelligent design in general rather than a specific writer's intelligent design argument; those wishing to reject intelligent design in general as un-scientific cannot simply critique one specific intelligent design argument--they must reject the basic argument (above) that intelligent design proposals have in common. This has proved exceedingly challenging to do, because the basic argument is shared with other scientific disciplines.
Specific proponents of intelligent design may build upon the basic argument any number of ways and, of course, it is certainly possible for a proponent of intelligent design to make other claims that are not scientifically rigorous (just as it is possible for an archeologist to make a great error), but it would be fallacious to throw out the basic argument because someone using it also said something else that was unscientific.
A specific application of the basic argument is specified complexity: complex information wherein a "precise arrangement of characters...allows the sequence to produce a specific effect" (Meyer, Darwin's Doubt p. 168) .
- P1 would be that intelligent agents are the only known cause of specified complexity.
- P2 would be that cells exhibit specified complexity.
Both of these claims are scientific in nature, as will be explored below.
Questions of demarcation
The OP provides 6 principals of demarcation as to what is scientific and what is not. The question of demarcation is itself complex (e.g. see Larry Laudan's The Demise of the Demarcation Problem), and aside from falsifiability, just about any proposed criteria for qualifying as "scientific" has exceptions (e.g. testability is a popular criteria, but much of theoretical physics fails the testability test; repeatability is a popular criteria, but studies of events in the past often fail the repeatability test, etc.)
Nonetheless, I'll offer a response to the 6 criteria that were suggested:
Falsifiability: Does Intelligent Design make testable predictions that, if proven false, would contradict its central claims?
The basic argument, applied to specific complexity, is highly vulnerable to falsification. Premise 1 could be falsified if a single example of naturally-occurring specified complexity were found. Premise 2 could be falsified if it could be shown that cells do not contain specified complexity. Both premises are based on data and can be tested.
A number of predictions have been made from the study of intelligent design--the most famous is that function would be found in so-called "junk DNA". This was predicted by William Dembski in 1998 and confirmed by the ENCODE project in 2012 (source).
Stephen Meyer provides a more thorough survey of predictions in Appendix A of his book Signature in the Cell. A few of them are briefly mentioned below:
- No undirected process will demonstrate the capacity to generate 500 bits of new information starting from a nonbiological source.
- Informational accounting will reveal that sources of active information are responsible for putatively successful computer-based
- Investigation of the logic of regulatory and information-processing systems in cells will reveal the use of design strategies and logic
that mirrors (though possibly exceeds in complexity) those used in
systems designed by engineers. Cell biologists will find regulatory
systems that function in accord with a logic that can be expressed as
- Sophisticated imaging techniques will reveal nanomachines (turbines) in centrioles that play a role in cell division. Other
evidence will show that malfunctions in the regulation of these
machines are responsible for chromosomal damage.
- If intelligent design played a role in the origin of life, but not subsequently, prokaryotic cells should carry amounts of genetic
information that exceed their own needs or retain vestiges of having
done so, and molecular biology should provide evidence of
information-rich structures that exceed the causal powers of chance,
necessity, or the combination of the two.
- If a designing intelligence acted discretely in the history of life, the various subdisciplines of biology should show evidence of
- The fossil record, in particular, should show evidence of discrete infusions of information into the biosphere at episodic intervals as
well as a top-down, rather than bottom-up, pattern of appearance of
new fossil forms.
- If the flagellar motor was intelligently designed and the type-3 secretory system devolved from it, the genes that code for the
bacterial flagellar motor should be older than those that code for the
proteins in the T3SS, and not the reverse. Alternatively, if the T3SS
and the flagellar motor arose by design independently, T3SS should
have unique (nonhomologous) genes that are not present in the genome
for the flagellar motor.
- The functional sequences of amino acids within amino acid–sequence space should be extremely rare rather than common.
Empirical evidence: What empirical evidence supports or refutes the claims made by Intelligent Design?
For premise 1: minds producing complex, functional information is a well-known phenomenon. Humans (who possess conscious minds) producing such information can be directly observed. I'm observing it right now while I type this. Generation of such information through natural processes has never been observed (note that computer software which generates novel information is acting upon instructions that were provided by an intelligent designer--aka a programmer). The Rosetta Stone (mentioned previously) is a clear example of something human minds are known to be able to produce, but wind and rain are not.
For premise 2: that DNA uses a chemical version of digital code is indisputable.
Methodology: Does Intelligent Design follow established scientific methodologies, such as proposing hypotheses, conducting experiments, and engaging in peer review?
Yes. Gathering examples of premise 1 would be supported by the same methodologies employed by archeology. Premise 2 is a direct result of hypotheses, experiments, and peer review that has elucidated the structure and function of DNA.
A number of falsifiable hypotheses were mentioned in the previous section.
Re peer-review, yes. A few examples:
by 2005 many excellent books and articles—including several important
peer-reviewed books—had already been published on different aspects of the theory of
intelligent design. In 1996, Lehigh University biochemist Michael Behe made a detailed
case for intelligent design based upon the discovery of nanotechnology in cells—such as
the now famous bacterial flagellar motor with its thirty-part rotary engine. Behe’s
Darwin’s Black Box sold over a quarter of a million copies and almost single-handedly
put the idea of intelligent design on the cultural and scientific map. In 1998, William
Dembski, a mathematician and philosopher with two Ph.D.’s ... followed suit by publishing a groundbreaking work on methods
of design detection. Dembski’s work, The Design Inference, published by Cambridge
University Press, established a scientific method for distinguishing the effects of
intelligence from the effects of undirected natural processes (Meyer, Signature in the Cell p. 9)
Consilience: Does Intelligent Design integrate with other scientific fields and theories, fostering a cohesive and interconnected body of knowledge?
Yes, the intelligent design movement was reborn in the late 20th century as a result of the discoveries of biology. It employs methods common to other historical sciences, such as geology or archeology.
Naturalistic explanations: How does Intelligent Design address the requirement of offering naturalistic explanations, which is commonly expected within scientific inquiry? (See methodological naturalism.)
Methodological naturalism is a means of testing a hypothesis. It does not require that the universe is in fact naturalistic. Metaphysical naturalism is a philosophical worldview that rejects all non-naturalistic explanations a priori.
Intelligent design employs methodological naturalism in the study of cells and information. The observable facts about cells that are addressed by proponents of intelligent design are not disputed by other professionals who study cells. The disagreement is on the inferences drawn from those facts.
Intelligent design does not employ metaphysical naturalism -- to do so would be to engage in philosophy, not science. Intelligent design may carry metaphysical implications, but rejecting a theory because it has metaphysical implications would also require rejecting the modern synthesis of Darwinism. (see Meyer, Darwin's Doubt p. 391)
Efforts to smuggle metaphysical naturalism into science are rather effectively exposed by comments such as the following statement by geneticist Richard Lewontin:
We take the side of science in spite of the patent absurdity of some of its constructs, in spite of its failure to fulfill many of its extravagant promises of health and life, in spite of the tolerance of the scientific community for unsubstantiated just-so stories, because we have a prior commitment, a commitment to materialism. It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is absolute, for we cannot allow a Divine Foot in the door" (Billions and Billions of Demons p. 28)
Lewontin said the quiet part out loud.
The claim that only naturalistic evidence and naturalistic explanations should be considered is itself unscientific: it isn’t falsifiable. Any non-naturalistic evidence (whatever that might be) would have to be discarded from consideration, and therefore be unavailable to falsify the claim. The a priori decision to rule “out of scope” any contrary evidence is as contrary to the scientific method as it is possible to be.
If defenders of the scientific method are looking for smuggling of philosophical worldviews into scientific inquiry, and they've settled upon intelligent design as a target, perhaps they are looking in the wrong direction.
(This is not to say that a proponent of intelligent design could not smuggle a theistic philosophical worldview into their work too--but the focus of this post is the idea of intelligent design in general, not a specific author's work. I won't reject biology as pseudoscience because some specific biologists have smuggled in metaphysical naturalism. However, the critical point to note here--commonly seen in academia and very bluntly admitted by Lewontin--is that mixing metaphysical naturalism with science is a problem occurring at a far greater scale in modern academia than is mixing theology with science)
Consensus within the scientific community: What is the general opinion among experts in relevant scientific disciplines regarding the recognition of Intelligent Design as a scientific theory?
Of the 6 criteria, this is where intelligent design will struggle the most. Experts in relevant scientific disciplines generally agree with the empirical claims about cells that are cited by proponents of intelligent design, but hostility towards the idea of intelligent design is exceedingly common. As the OP noted in comments elsewhere, cross-posting this question to multiple Stack Exchange sites has been an interesting social experiment, and it has laid bare examples of this hostility.
A representative example is the publication--and later apology-- by the Proceedings of the Biological Society of Washington of a biology-based argument for intelligent design in 2004. When the Society apologized for publishing the article:
it did not invite a scientific refutation of the article, as if the problem had been a misrepresentation or misinterpretation of the evidence. Instead, it attempted to settle the issue by releasing a policy statement. As a writer in the Wall Street Journal reported at the time, "The Biological Society of Washington released a vaguely ecclesiastical statement regretting its association with the article. It did not address its arguments but denied its orthodoxy." (Meyer, Darwin's Doubt pp. 384-385)
A more detailed discussion of the incident, and the retaliation & defamation suffered by the editor who originally agreed to the article's publication, can be found here.
So the general consensus of the scientific community is not favorable towards intelligent design. However, as a challenge to the validity of this criterion, it is worth acknowledging that Galileo's model of heliocentrism, Newton's theory of gravitation, more recently the theory of plate tectonics, and other major advances in scientific knowledge, were originally rejected sharply by the scientific community1.
Engaging with other views
US court ruling
The US court system is often cited as an authority for determining that intelligent design is pseudoscience. I am at a loss as to why--save desperation--one would appeal to judges to defend this claim.
Furthermore, this is the same court system that decided that tomatoes are vegetables, and, far more consequentially, decided that some human beings are sub-human or "not human persons". The Dred Scott decision should give pause to anyone using the US court system in an argument from authority on matters of science or philosophy.
It is easy to make an apples-to-oranges comparison in a discussion of complex information. If we are trying to distinguish between information generated by a mind and information generated by something else, the amount of information is not terribly useful on its own. Supercomputers generating random words can quickly generate more information that the entire literary output of humanity prior to the 20th century, but those random words would not have much functional meaning. For a random process to generate the works of Shakespeare, the time needed would be far, far beyond the entire lifetime of the universe (see here).
"Shannon information" considers the amount of uncertainty removed by a piece of information--it's focus is on the complexity of the information. However, it says nothing about the specificity or the function of that information.
Intelligent design isn't focused on Shannon information, it is focused on specified complex information. Comparisons showing that machines (or anything else) can produce large quantities of Shannon information are quite irrelevant to intelligent design.
Are tree rings--preserving meteorological details from past years--an example of naturally occurring specified complexity?
This is an interesting idea...but I do not see how tree rings meet the burden of proof. Scientists can construct an intelligible "message" describing high-level meteorological details by lining up tree rings for past years. But unlike human language, DNA, or computer code, the tree rings could be rearranged in any possible sequence and still produce an intelligible message. The message would be false in all but 1 of these arrangements, but whether a message contains specified complexity and whether a message is true are entirely independent variables.
For several million corroborating examples that these variables are independent, see the collection of specified complexity on this website: www.twitter.com
Some see AI as a possibility to reject the claim that only intelligent minds produce specified complexity. To date, AI has not done this--it still relies upon programmers to provide specified complexity, goals, prompts, training files, etc.
The future of AI invites all manner of interesting questions. AI may at some point refute the claim that only intelligent minds produce specified complexity -- and proponents of intelligent design should be open to falsification of this hypothesis. But appeals to what AI may do in the future are simply begging the question. Claiming that AI will do this is assuming the very thing that needs to be proven.
The basic argument for intelligent design is scientific in the same way that archeology is. It is falsifiable, it allows predictions to be made, and it makes inferences to the best explanation.
That some specific proponent of intelligent design has been less-than-rigorous in their scientific inquiry does not indicate that the basic argument itself is unscientific or cannot be used in rigorous, scientific research.
If intelligent design is seen as a threat to the dogma of metaphysical naturalism, that's a good thing. If there are those who oppose intelligent design out of a desire to protect rigorous scientific inquiry (rather than out of preference for metaphysical implications), we should reasonably expect that such individuals are even more passionate in eliminating metaphysical naturalism from science.
1 - Because I mentioned Galileo there's an obligatory footnote. Common wisdom says that Galileo was on the side of science and he was rejected by "big religion", providing a clear example of the dangers that religion poses to science. Besides the fact that it was Galileo's Christian faith that led him to ask the questions he did, the "common wisdom" does not in fact describe what occurred. Abuse of power is not a feature specific to religion, it is a feature general to human nature. But Galileo wasn't rejected by blind appeal to dogma--Galileo had scientific critics who recognized the weakest point in his hypothesis and used it to reject his claims: stellar parallax. Galileo's claims relative to stellar parallax were confirmed in 1838, but at the time many academics treated Galileo's work as the 17th-century equivalent of pseudoscience.