Occam's
Razor

Your message sits unanswered for a day. You reread it for a hidden insult, replay your last conversation for signs of tension, and start drafting an apology for something you cannot name. She was simply busy, and you spent the day solving a problem that never existed.

What is Occam's Razor?

Occam's Razor is a problem solving rule that tells you to prefer the explanation which needs the fewest assumptions to be true. When several explanations could fit what you see, you count what each one asks you to assume, and you begin with the one that asks for the least. The simplest explanation is not guaranteed to be right, yet it is the most likely and the cheapest to check, so it is where you start. The rule takes its name from William of Ockham, a medieval friar who argued against multiplying assumptions beyond need.

Every extra assumption in an explanation is one more thing that must be true for the whole story to hold, and each one can fail. A story with five moving parts has five chances to be wrong, so it is far less likely than a story that rests on one. Starting simple means you test the most probable cause first, so you usually find the answer before spending any effort on elaborate explanations that were never needed.

How to use it

Use it whenever you catch yourself building a complicated story. Five steps keep you honest.

  1. Write down the explanation you jumped to.
    Put your current theory in plain words, including everything it quietly assumes. Seeing it written makes its moving parts visible.
  2. List the simpler explanations you skipped.
    Force yourself to name the plain, boring possibilities: they were tired, they forgot, the battery died, you misread the time. Ordinary causes are common for a reason.
  3. Count the assumptions each explanation needs.
    For every option, tally what has to be true for it to hold. "My friend is angry" needs a reason, a memory, and a motive. "She was busy" needs nothing but a normal day.
  4. Start with the fewest and check it first.
    Pick the explanation resting on the least, and test that one before any other. Send a light follow-up before you send an apology, and let the simple check settle it.
  5. Add complexity only when the simple answer fails.
    If the plain explanation turns out wrong, move to the next-simplest, adding assumptions one at a time rather than leaping to the elaborate story.

Worked example

Your car makes a new rattling sound on the drive to work. Your mind goes straight to the expensive possibility: the engine is failing and a large repair bill is coming. You picture the garage, the loaner car, and the dented savings, all before you have looked at anything.

You stop and apply the razor. You list simpler causes first: a loose water bottle, a stone caught in the wheel trim, a pebble in the tread. Each of these needs almost nothing to be true, while "the engine is failing" needs a whole chain of problems to line up. You check the cheap options first and find an empty can rolling around in the boot. Two minutes of looking saved you a day of worry, because you tested the simple cause before the frightening one.