The third morning of Kitzmiller vs. Dover found philosopher of science Robert Pennock testifying for the plaintiffs that science is a search for natural explanations of natural phenomena--a limitation known as methodological naturalism (or methodological materialism).
Pennock presented this as the definition of science, and said proponents of intelligent design are “trying to overturn" it, but later he conceded that there was a controversy among philosophers of science concerning whether methodological naturalism was essential to the definition of science.
Interestingly, Miller and Pennock each invoked a counterfactual in their defense of methodological materialism, so in the interest of aesthetic balance, let’s consider their argument. They said an omnipotent designer could have made the universe a few minutes ago and given us all false memories to make us think it was old. Thus, someone could entertain any sort of design scenario for anything and everything. But where would science be if everybody thought that way. The solution they offered? Methodological naturalism.
But this is the slippery slope fallacy: If we let a designing foot in the door, then before you know it our brains will turn to jelly and we’ll be invoking design at the least drop of a hat.
The best cure for one form of irrationality isn’t to flee into the opposite irrationality. The founders of modern science--e.g., Copernicus, Kepler, Newton--were open to evidence of design, and clearly their brains didn’t turn to jelly. Between the unreasonable extremes of hyper-skeptical illusionism on the one hand and unbending methodological materialism on the other lies the path of reason. One can remain open to the possibility of design and go right on being rational and measured, go right on looking hard for new and more elegant regularities in nature that were previously a mystery. In some cases, the researcher will do both at one and the same time, as when astrobiologist Guillermo Gonzalez and philosopher Jay Richards elucidated a cosmic correlation between habitability and discoverability, and from this inferred intelligent design.Do yourself a favor and read the whole thing.
For an even more recent example of the slippery slope at work, check out this post by CelticBear, who accuses proponents of I.D. of "attacking natural sciences" and adds:
We already have a battle of pseudo-science in the public arena with crystals and ESP and UFO’s and Ouija boards and Tarot cards and astrology and other crap. Any of these things which base themselves on non-naturalistic concepts prove to advance science at all? Oh, how’s that Christian Science based belief of prayer is all you need working out? Save a lot of kids with leukemia has it? How’d you like to fly in a plane designed by someone who based his knowledge of aerodynamics on prayer? Or used Biblical knowledge to create an antibiotic? Or trusted in God to give him the knowledge to understand the effects of gravity, solar flares, cosmic radiation, and space vacuums when designing that spacecraft? If all knowledge should be revealed by God as it has been from 4000 BC, then there’s no reason to explore space at all in any case. Nothing out there that can’t be known through prayer and reading the Bible.