But Occam’s razor is often fetishized and misapplied as a guiding beacon for scientific enquiry. It is invoked in the same spirit as that attested by Newton, who went on to claim that “Nature does nothing in vain, and more is in vain, when less will serve.” Here the implication is that the simplest theory isn’t just more convenient, but gets closer to how nature really works; in other words, it’s more probably the correct one.

There’s absolutely no reason to believe that. But it’s what Francis Crick was driving at when he warned that Occam’s razor (which he equated with advocating “simplicity and elegance”) might not be well suited to biology, where things can get very messy. While it’s true that “simple, elegant” theories have sometimes turned out to be wrong (a classical example being Alfred Kempe’s flawed 1879 proof of the “four-color theorem” in mathematics), it’s also true that simpler but less accurate theories can be more useful than complicated ones for clarifying the bare bones of an explanation. There’s no easy equation between simplicity and truth, and Crick’s caution about Occam’s razor just perpetuates misconceptions about its meaning and value.

The worst misuses, however, fixate on the idea that the razor can adjudicate between rival theories. I have found no single instance where it has served this purpose to settle a scientific debate. Worse still, the history of science is often distorted in attempts to argue that it has.

Take the debate between the ancient geocentric view of the universe—in which the sun and planets move around a central Earth—and Nicolaus Copernicus’s heliocentric theory, with the Sun at the center and the Earth and other planets moving around it. In order to get the mistaken geocentric theory to work, ancient philosophers had to embellish circular planetary orbits with smaller circular motions called epicycles. These could account, for example, for the way the planets sometimes seem, from the perspective of the Earth, to be executing backwards loops along their path.

It is often claimed that, by the 16th century, this Ptolemaic model of the universe had become so laden with these epicycles that it was on the point of falling apart. Then along came the Polish astronomer with his heliocentric universe, and no more epicycles were needed. The two theories explained the same astronomical observations, but Copernicus’s was simpler, and so Occam’s razor tells us to prefer it.

This is wrong for many reasons. First, Copernicus didn’t do away with epicycles. Largely because planetary orbits are in fact elliptical, not circular, he still needed them (and other tinkering, such as a slightly off-center Sun) to make the scheme work. It isn’t even clear that he used fewer epicycles than the geocentric model did. In an introductory tract called the Commentariolus, published around 1514, he said he could explain the motions of the heavens with “just” 34 epicycles. Many later commentators took this to mean that the geocentric model must have needed many more than 34, but there’s no actual evidence for that. And the historian of astronomy Owen Gingerich has dismissed the common assumption that the Ptolemaic model was so epicycle-heavy that it was close to collapse. He argues that a relatively simple design was probably still in use in Copernicus’s time.