‘Life Is Simple’ Review: A Blade to Shave Away Error

Mr. McFadden is professor of molecular genetics at the University of Surrey in England. His interest in Occam was sparked by a daily commute which took him past the village of Ockham, where William was born, probably around 1287. Little is known about William’s early life, but by his thirties his writings on philosophy and theology were widely read—and highly controversial.

Occam challenged the prevailing belief that objects were manifestations of archetypal forms that were themselves real. As Mr. McFadden explains, “Cherries were cherries because they shared in the universal of ‘cherryness.’ ” Occam instead proposed what became known as nominalism. “[He] argued that universals are merely the terms that we use to refer to groups of objects.” Occam shaved universals out of existence, saying, “It is vain to do with more what can be done with less.”

The conventional view was that an object’s qualities—such as color, texture or weight—had a separate existence from the object itself. This was how theologians explained the Eucharist, when bread and wine became the body and blood of Christ. God could transform substance while leaving appearance unchanged. Occam’s nominalism cast doubt on that, and in 1324 he was summoned to a papal court in Avignon. The proceedings dragged on for four years until Occam managed to escape to Germany, where he died nineteen years later. The Munich church where he was interred no longer exists, but Mr. McFadden reports that near the site there is “a Hotel Occam and a very convivial deli and wine bar called Occam Deli.”

Mr. McFadden’s book is itself a multicourse meal with a variety of ingredients. After the story of Occam’s life has been told, the friar’s two big ideas—nominalism and the razor—remain as heroes, portrayed as the driving spirit that enabled science to blossom. The author takes us from the epicycles of Ptolemaic astronomy to the multiverse of modern-day superstring theory, via Newton, Darwin, Einstein and many others, including the influence of Occam’s thought on painters, poets, musicians and political philosophers across the centuries. The encyclopedic range will certainly appeal to some information-hungry readers, though at times during this all-you-can-eat buffet, the idea of doing more with less gains appeal.

Occam’s nominalism may seem like plain common sense, in contrast to the metaphysical universals he opposed. But rather than cherries, what about science? Is it merely a name we give to a set of activities by people called scientists, or a universal principle with absolute standards? Mr. McFadden takes the latter view. As he puts it, “Science is simplicity.” The Sun-centered cosmology of Copernicus was simpler than Ptolemy’s geocentric one, Kepler’s three laws of planetary motion were simpler than either, and Newton showed how all three could be explained by a single law of gravitation.

Yet scientific “simplicity” itself proves to be surprisingly complex. Newtonian physics gave way to the theories of relativity and quantum mechanics. A physicist would say those are simpler because they explain a wider range of phenomena, based on fewer assumptions, and with greater accuracy. A student struggling to understand them might say otherwise. Mr. McFadden offers his own way of quantifying simplicity, which he calls “Occam’s pocket razor.” He suggests counting “the number of significant words (excluding articles, conjunctions, etc.) required for rival explanations or models and punishes the lengthier by halving its probability for every significant extra word.” With this little rule he deduces that “the heliocentric system is two to the power of seventy or about a million billion fold more likely than the geocentric model.”

It is when dealing with biology—his own specialist field—that Mr. McFadden is at his most interesting and illuminating. He informs us that the torpedo fish was named centuries ago for its mysterious ability to stun its prey—i.e. to induce torpor. Understanding its baffling abilities awaited later discoveries about electricity.

By contrast, the coverage of physics and chemistry in “Life Is Simple” feels much like the standard account found in numerous other books. There’s only room for so much: Galileo’s astronomical discoveries are well covered, but his later downfall is summarized as “a story that has been told many times.” That’s an unfortunate omission, since Galileo’s complicated dealings with the Catholic Church illustrate both the influence of Occam’s philosophy and the limitations of his razor.

In 1616, six years after first announcing his astronomical discoveries, Galileo swore an oath before a Vatican official, agreeing not to promulgate the Copernican model. Seven years (and two Popes) later he published “The Assayer,” a book notionally about comets but also containing many other ideas. One was his famous remark about the universe being written in the language of mathematics; another was a theory of atoms. Galileo’s idea of “fire-corpuscles” was wrong, but he drew an important conclusion: Odors, tastes and sounds are sensory impressions caused by atoms, not things with independent reality. This was nominalism, as one of Galileo’s opponents was quick to inform the Inquisition, which nevertheless took no further action. Galileo later wriggled round his earlier oath by putting proof of Earth’s motion into the mouth of a fictional character in a 1632 dialogue. Never mind that the “proof”—Earth’s tides—was wrong; Galileo also put the views of the Pope in the mouth of an Aristotelian stooge named Simplicio. Factions that had long been gunning for Galileo finally had their chance to bring him down. He spent his remaining years under comfortable house arrest where he refined his theory of atoms, which he thought were of no size, held together by suction. A simple theory—and simply wrong.

Occam’s Razor is good at telling us in retrospect why some theories have triumphed over others, but what it can’t do is spot winners in advance. That makes it a blunter instrument than Mr. McFadden would have us believe. Life may be simple, but history is complex.

—Mr. Crumey is the author, most recently, of “The Great Chain of Unbeing.”