Occam's Razor

You wake up and the yard outside your window is soaking wet. Which is the more natural thought: it rained overnight? Or a neighbor secretly dragged over a water tank, sprayed the whole yard, and ran off?

Both can explain why the ground is wet. But the second explanation needs far too many unnecessary assumptions that you would have to prove, like "why did the neighbor do it?" and "how did they spray all that water without a sound?" The rain explanation needs just one fact: the weather.

The 14th-century philosopher William of Ockham liked to use the principle "do not assume more than you need," and later people named the principle after him. It means that when several claims explaining the same thing collide, you should boldly cut away the pointless assumptions. Just as you trim a shaggy beard neatly, let's shave off extra explanations like a razor.

The same goes for the many questions we meet in daily life. The more premises and guesses stuck onto a complicated story, the more likely it is to drift away from the truth.

Medical schools teach students, "When you hear hoofbeats, think horses, not zebras." When a patient has a fever and a cough, it makes much more sense to suspect a common cold or the flu first, before suspecting a very rare tropical disease.

In scientific research, this principle has always had real power. Once Kepler worked out that the planets travel around the Sun in ellipses, the complicated circular orbits that had been piled onto the idea of Earth as the center of the universe were no longer needed.

Conspiracy theories sound appealing for a similar reason. They add a huge secret organization's plot to an event that ordinary mistakes or coincidence could explain. To think logically, you need the habit of checking the simplest, clearest cause first.

When we explore new facts, too, it is much safer to take the first step from facts that have already been checked than to keep piling on unproven hypotheses.

There is one thing to watch out for here. Occam's razor is not an absolute law of nature that guarantees the simple answer is always 100% true. The real world sometimes works in ways far stranger and more complicated than we expect.

For example, observations that classical physics could not explain (like the shift in Mercury's orbit) kept piling up, and relativity, which needs more complicated math, came to be accepted. The razor says to pick the simpler explanation when the explanatory power is equal. So when a theory with greater explanatory power appears, you choose that one.

So Occam's razor should be understood not as "believe only the simple thing, no matter what," but as a practical guideline: look at the simplest hypothesis first. It is like a detective starting an investigation by checking the most likely suspect first, then moving down the list.

A more complicated explanation can still be accepted later, once solid, new evidence turns up to support it.