Occam’s razor (also spelled Ockham’s razor) cuts through complexity with a no-nonsense approach. The philosophical maxim “Numquam ponenda est pluralitas sine necessitate”, written by the 14th-century Franciscan friar William of Ockham, translates to “plurality must never be postulated without necessity”. In other words, all else being equal, simplicity is best.
So is that actually true? Is the simplest explanation usually the best?
Not exactly. Ockham never said that complexity is inherently inferior to simplicity, nor did he argue that complex explanations are inherently wrong. Complex scientific questions often require complex answers, and that’s not at odds with Occam’s razor. The principle simply states that unnecessary complexity is, well, unnecessary.
“Occam’s Razor is about finding the simplest solution that works.” John Joe McFadden (opens in new tab)Professor at the University of Surrey in Great Britain and author of the book “Life Is Simple: How Occam’s Razor Freed Science and Shaped the Universe (opens in new tab)(Basic Books, 2021), Live Science said in an email. “It never fails as long as you remember the necessity clause.”
Ockham was not the first (opens in new tab) promote simplicity. Aristotle held that “the more limited, when appropriate, is always preferable”, and Ptolemy thought it best “to explain phenomena by the simplest possible hypothesis”. Some three centuries after the creation of Occam’s razor, Isaac Newton declared that “we ought to admit no more causes of things natural than those which are both true and sufficient to account for their appearance”. Some 200 years later, Albert Einstein would agree that “everything should be made as simple as possible, but not simpler” (which is actually a simplification on his part original quote (opens in new tab)).
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When used correctly, Occam’s razor works. When two computer programs perform the same task, it is bound to be more efficient with less code. The simplest medical diagnosis is usually correct; Hospital interns are often taught to think of horses and not zebras when they hear hoofbeats. An implication of Second law of thermodynamics (Clutter increases with every spontaneous process) is that such processes always consume the least possible energy.
“Copernicus developed the heliocentric model of the solar system solely on the basis that it was simpler,” McFadden said. “The existence of a single Higgs boson was the simplest solution to the equations of particle physics. Between these points lie a thousand scientific advances that depend on simplicity.”
However, when misused, Occam’s razor can become a blunt instrument of overgeneralization. For example, the principle does not mean that we blindly follow the simplest theory, right or wrong. “Very often the simplest hypothesis is too simple” Elliott Sober (opens in new tab)Professor of philosophy at the University of Wisconsin-Madison and author of “Occam’s Razor: A User’s Guide” (opens in new tab) (Cambridge University Press, 2015), Live Science said in an email. “The simplicity of a hypothesis is one consideration among others relevant to assessing whether a hypothesis is true.”
When it comes to data science, Occam’s razor can cause more problems than it solves. In this case, “the simplest approach is often wrong,” he said Pedro Domingos (opens in new tab), Professor Emeritus of Computer Science and Engineering at the University of Washington in Seattle. When Domingos examined the applicability of Occam’s razor to machine learning in the early 2000s, he found that a easier (opens in new tab) model (opens in new tab) is superior to a complex one only if it can predict new data just as well.
“As modern machine learning has shown time and again — in model ensembles, deep learning, etc. — it’s usually the most complex approach that’s right,” Domingos told Live Science in an email. “And that’s not surprising; The phenomena we model are almost always more complex than the models, and the closer we get to their true complexity, the more accurate the models become.”
Nonetheless, Occam’s razor remains a useful tool for stripping the fat from bulky assumptions, at least in our daily lives. “The universe is a complicated place, but it’s sometimes made more complicated by the invention of complicated explanations that fit a particular ideology, philosophy, or political belief,” McFadden said. “Occam’s razor tells you to forget all that.”