I’m in trouble with some creationist readers for having used the phrase “folk metaphysics” once too often over at National Review Online. What do I mean by it, they demand to know. Is it just another way of scoffing at those brave, independent souls who refuse to accept the brutish, materialistic Dictatorship of Darwinism?

Of course it is! But more than that too. Let me explain.

Folk metaphysics is the standard-issue set of notions our brains come equipped with to help us navigate our way around the everyday world, the world of what one philosopher called “medium-sized dry goods.”

For those purposes, folk metaphysics is excellent, and we all use it all the time. It includes cast-iron rules like “a thing can’t be in two places at once” and “the burning-up of a thing is irreversible.” There are more general principles like the living-nonliving division of matter and the slightly more sophisticated animal-vegetable-mineral one, or the “like can only come from like” rule (e.g. fishes don’t produce kittens)—in itself one instance of a bigger, more general group of folk-metaphysical ideas called “sympathetic magic.”

Then there are more approximate rules of thumb like “large solid objects are apt to be heavier than small ones” and “anything moving in a purposive way is an animal, or is pushed or pulled by one” (which is why Apaches, applying straightforward folk metaphysics, assumed there was a horse in the locomotive).

We all use these notions all the time, and are surprised, even sometimes disturbed, when they are violated—when, for example, a large solid-looking object turns out to have little weight. They’re terrifically useful, and are nothing to scoff at in themselves. Their instantiations in our nervous systems took hundreds of millions of years to evolve. Our thoughts are all wrapped around them, and our languages are wrapped around our thoughts. So really, nobody should be scoffing at folk metaphysics per se. You might as well scoff at your taste buds, or binocular vision. Folk metaphysics is just part of the neurological equipment.

As soon as you conduct a rigorous inquiry into reality, though, problems arise. This has been clear for a couple of hundred years, so stubborn resistance to it is, I think, scoff-worthy—the willful denial, for private psychological purposes, of something in plain sight.

Sodium is a poisonous metal; chlorine is a poisonous gas; put them together in chemical combination and you get sodium chloride—common table salt—which is neither poisonous, nor a metal, nor a gas. Whoa, what happened to “like can only come from like”? Evolution violates the same principle, which is why the mind resists it. Even Newton’s dull old laws of motion contradict folk metaphysics to some degree.

Sir Isaac: An object in uniform motion stays that way until a force is applied.

Folk Metaphysician: No it doesn’t. Objects set moving on the level always roll or slide to a stop. Things moving through the air fall to the ground, unless they’re flying. On water, things get carried every which way by currents, and sometimes sink.

Sir Isaac: Apply a constant force to a constant mass, you’ll get steady acceleration.

Folk Metaphysician: A horse pulling a wagon is applying constant force to constant mass, isn’t it? So if your so-called “law” is true, why wasn’t 19th-century America full of horses and wagons zipping around at hundreds of miles an hour? Huh?

Sir Isaac: Every action generates an equal and opposite reaction.

Folk Metaphysician: So when I push on this wall with my hand. the wall pushes back? What, there’s a little hand in the wall pushing back at mine? Hoo hoo hoo! How’s it know when to stop pushing? Ha ha ha ha!

These violations notwithstanding, folk metaphysics, with a little jury-rigging, held together pretty well through to at least the 1870s, when William Clifford could title a book The Common Sense of the Exact Sciences. (Which did, though, allow the very un-folk-metaphysical notion of curved three-dimensional space.)

Then things went haywire, 20th-century physics delivering results grossly and utterly incommensurable with folk metaphysics. A thing can be in two places at the same time. Different observers, with identical instruments, will get different measurements for the length of a thing… and so on.

The 21st century promises to offer further insults to the folk metaphysician, mostly in the biological and human sciences. The living-nonliving distinction is already long gone. The citadel of mind-matter dualism is under siege, though its walls are still intact as we go to press here, and I personally wouldn’t put a big bet on anything, though emergentism looks to me to be worth a flutter.

Folk metaphysics, while mighty useful for getting around among those “medium-sized dry goods,” is pretty hopeless as a guide to the deep structure of reality.

And the larger moral of the story is that finding out true facts about the world—science—is a social enterprise. The individual human mind isn’t going to be much good at it. There’s too much folk-metaphysical clutter; and, at a deeper level, the sorts of necessary limitations in our perceptual apparatus that Kant told us about.

So two cheers for folk metaphysics; but, if you’re planning to live a few more decades, brace yourself for some violations of it as outrageous as those inflicted on us by Einstein and the quantum theorists, but in areas of knowledge much closer to home.