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What is Occam's razor?

PhilosophyLesson on requestFree to read

Quick answer

Occam's razor is the principle that, when several explanations fit the facts, the simplest one — with the fewest assumptions — is usually the best place to start. It doesn't guarantee truth, but it's a powerful guide in science and reasoning.

Key things to understand

  1. Prefer the explanation that makes the fewest assumptions.
  2. It's a guideline for choosing between competing theories, not a proof.
  3. Simpler explanations are easier to test and less likely to be wrong by chance.
  4. It's named after medieval philosopher William of Ockham.
  5. It underpins the scientific habit of not multiplying assumptions needlessly.

People also ask

Does Occam's razor mean the simplest answer is always true?
No — it says the simplest adequate explanation is the best starting point, but stronger evidence can still favor a more complex one.
Why prefer simpler explanations?
They rest on fewer unproven assumptions, are easier to test, and have fewer ways to be accidentally wrong.
Where is Occam's razor used?
In science, medicine, detective work, and debugging — anywhere you choose among explanations that all fit the facts.