As useful and successful as metal detectors are, they can’t be used to find everything. Metal detectors won’t help you find wood, plastic, rubber, or other nonmetallic objects.
Now, suppose metal-detector man, after just combing the beach, says to you, “I know there’s no plastic or rubber on that beach because I looked for those things with my metal detector and found nothing!” Then suppose he goes even further and says, “There’s not only no plastic or rubber on that beach, there is no plastic or rubber anywhere because I’ve never found a speck of it with my metal detector!” Meanwhile, you can’t help but notice that his metal detector is made of mostly plastic and rubber.
You’d think, “Is metal-detector man nuts? He’s certainly not thinking properly.”
That’s what Dr. Edward Feser, who thought of this illustration, thinks about atheists who insist that all truth comes from science. The atheists are like metal-detector man, and science is their metal detector. Because their chosen tool — science — has been so successful in discovering material causes in the natural world, atheists mistakenly assume that nothing but material things exist. And just like metal-detector man doesn’t realize that plastic and rubber are part of his metal detector — in fact, it couldn’t work without them — some atheists don’t seem to realize that immaterial realities are part of science, and science couldn’t work without them.
When the new atheists (such as Richard Dawkins and Sam Harris) refer to “science,” they are normally referring to the study of material causes in fields such as physics, chemistry, biology, cosmology and astronomy. There’s obviously much to gain by studying those areas of reality. The problem arises when the new atheists assert that those are the only areas of reality — that everything can be explained by material causes, and all truth comes from science.
Such an assertion is obviously false. In fact, the claim “all truth comes from science” didn’t itself come from science. It’s not a scientific truth, but a philosophical claim about science. So the claim is self-defeating.