“Those enchanted princes can do anything,” says the wife of the fisherman who catches a wish-granting flounder that happens to be an enchanted prince. This is not a truth universally acknowledged in our humdrum world, so lacking in magical fish. And yet here, in this one story, the power of enchanted princes is axiomatic, as fundamental as gravity. You can hear trouble coming in the wife’s words, as surely as if this story were by Sophocles. This is one of the “Children’s and Household Tales” collected by the Grimm brothers in the early 19th century. In that fictive world, trouble comes abruptly and in threes.

The Grimm brothers’ tales have been newly retold by Philip Pullman, author of the wonderful trilogy “His Dark Materials.” His goal is to make these tales, first published in 1812, “as clear as water,” as clear as they were when the Grimms first gathered them from a wide array of sources. I hadn’t reread the tales in years, and perhaps I had never really read them, having merely absorbed them from the air around me, where they abide like a haunting cultural mist. I knew only the simplest versions, which lacked many of the twists and turns in the originals. But what they really lacked was any sense of the laws that govern the many realms of these tales. There are witches and wicked stepmothers, of course, but also talking ravens and snakes bearing life-giving leaves. And as retold by Mr. Pullman, the tales reveal what you might call an inviolable physics — laws without which the tale-world (there is surely a German word for this) would come apart.

These laws sound like embroidered samplers you might find hanging in a witch’s kitchen. “If you’ve given in once, you have to give in forever.” That’s from Mr. Pullman’s “Hansel and Gretel.” Or, “Nothing tastes as good as what you eat by yourself,” from “The Cat and the Mouse Set Up House.” To a child, the Grimm rules are no more surprising than the rules of everyday life. That’s part of their enchantment. In fact, they call into question, as Lewis Carroll did, what often passes for conventional wisdom. “Beggars can’t be choosers.” But who says? Would a choosy beggar belong to our world or the Grimms’?

The tales — and most of the rules within them — are completely discontinuous. Enchanted princes clearly can’t do anything, for instance, or they wouldn’t be flounders. We’re not allowed to wonder whether the mouse that set up house is the one that later moves in with a talking sausage. Nor do the laws lead to the moral of the story. Most of the tales lack anything so simple. Read them through, and you realize that there are any number of kings — kings everywhere! — but very few lessons to instill in a child.