What would it take to justify the claim that there are propositions such that the discovery of evidence against them can qualify as science, but evidence in favor of them cannot? Someone who accepts this view would probably extend it to propositions about ghosts or extrasensory perception. Research showing that effects that some benighted souls have attributed to ghosts or mental telepathy can be explained in a perfectly naturalistic way would count as science, but any argument that the evidence does not support those explanations, and that significant experimental or observational data are better explained by ghosts or by ESP, would not count as science, and could therefore be ruled out of consideration. On this view it would not even be a false scientific claim.
With regard to ghosts, I don't know what effects Dr. Nagel could be talking about about. How do you test for the presence of a ghost? How do you verify this is a successful test? I have seen magicians duplicate the feats of various psychics, while claiming is it all based on natural abilities, so you can't rely on physics to tell you if there are actually ghosts present. This is outside of science because we can not even verify if we have a functional test.
With regard to telepathy, and various other forms of ESP, there have been a variety of scientific studies done to determine if there is an effect to study. To my knowledge, all of the tests, when performed under controlled conditions, have determined that there is no reliable effect to study. If ESP is something that is supposed to used reliably at need, or under specific, reproducible conditions, then you obviously can study it scientifically. However, if ESP is presumed to be a phenomenon that appears and disappears without warning, for no reason, then it is immune to study because you can never have a true negative result.
It seems to me that in this respect ID is very different from young earth creationism, and the “creation science” that it spawned. There are people who believe, on the authority of the Bible, that God created the earth and all the creatures on it about six thousand years ago. The fact that this proposition is inconsistent with various scientific theories of cosmology, geology, and biology does not make it a scientific claim.
The claims of creationists may not be in agreement with science, but they can certainly be investigated by science. The very fact that there is a disagreement with science means that some sort of claim about science is being made. So, the fact that this proposition is inconsistent with various theories cosmology, geology, and biology does make it a scientific claim. It is a claim that leads to predictions of what we should expect to see with regard to cosmology, geology, and biology. Some scientific claims are just wrong.
Biblical literalism is not a scientific hypothesis because it is not offered as an explanation of the empirical evidence, but is accepted as a divine revelation. So long as no observations about the natural world are offered in its support, it is not even a false scientific claim. When, however, in response to the finding that the teaching of creationism in public schools was unconstitutional, the producers of creation science tried to argue that young earth creationism was consistent with the geological and paleontological evidence, they succeeded in putting forward a scientific claim, even though their reason for doing so was that they believed it to be true on other grounds, and their arguments were easily refuted.
When the assumption of a six-thousand-year-old earth led to predictions and interpretations that were scientific claims, it was because the original claim was scientific.
A scientific hypothesis can be false and unsupported by the evidence. That is a good enough reason not to teach it to schoolchildren. It is not necessary to argue that it is not science, not even hopelessly bad science.
Well, at least we agree here.
ID is very different from creation science. To an outsider, at least, it does not seem to depend on massive distortion of the evidence and hopeless incoherencies in its interpretation. Nor does it depend, like biblical literalism, on the assumption that the truth of ID is immune to empirical evidence to the contrary. What it does depend on is the assumption that the hypothesis of a designer makes sense and cannot be ruled out as impossible or assigned a vanishingly small probability in advance.
What ID has not done, does not do, and apparently will never do is give us a prediction about the world, a scientific claim, that can be tested. Regardless of how likely you think the notion of a designer is, the question remains: what is the testable evidence of a designer's footprints? Can you devise a functional, scientific test for a designer's involvement? We can rule out or confirm any designer that gives us a prediction, a testable entity. ID has not produced this entity.
Once it is assigned a significant prior probability, it becomes a serious candidate for support by empirical evidence, in particular empirical evidence against the sufficiency of standard evolutionary theory to account for the observational data. Critics take issue with the claims made by defenders of ID about what standard evolutionary mechanisms can accomplish, and argue that they depend on faulty assumptions. Whatever the merits, however, that is clearly a scientific disagreement, not a disagreement between science and something else.
I agree that many of the anti-evolution presented are at least arguments about science, and can be discussed in that venue. However, until ID can offer us something to make predictions, something to test, ID can never be science, no matter what the status of evolution.