Occams Razor

The Best Explanation Has The Fewest Assumptions

What is Occams Razor?

Occams razor is credited to William of Ockham, a 14th-century Franciscan friar, theologian and philosopher.

In philosophical debate a razor is an abductive rule of thumb or heuristic that infers that unlikely predictions, or explanations, are to be "shaved off" on balance of probability.

It is also referred to as a law of parsimony which is a principle that says that: ‘Entities should not be multiplied without necessity.’ (In Latin, Entia non sunt multiplicanda praeter necessitatem.)

However, it seems that William of Ockham never actually said this in any of his writings!

In plain modern english, Occams razor, or the law of parsimony, means that:

The best explanation is the one that requires you to make the fewest possible assumptions about what's involved.

• It is important to note that the razor is only applied to competing hypothesis about the same prediction.
• Occams razor will select the solution with the fewest assumptions.
• Simpler hypotheses are preferable to more complex ones because they are more testable.
• Occams razor is not meant to be a way of selecting hypotheses that make different predictions.
• It can not be used as to establish an irrefutable principle of logic,
• It can not be used to confirm the truth of a situation.
• It is definitely not to be considered as a scientific proof.
• It does not prescribe oversimplification, if a more complex theory is available that better explains the facts, then the more complex theory should be preferred.
  

• It is a mental model to be used as a part of a toolbox or portfolio of thinking skills for making initial conclusions before the full scope of information can be obtained.

---

Exceptions To Occams Razor

There are exceptions to every rule:

• Simplicity alone is not enough. A conclusion must be backed by empirical evidence.
• Blind faith is not enough, no mental model shoudl be relied on when it is contradicted by logic, experience, or empirical evidence.
• We must be aware of falling prey to cognitive biases.
• Because the world is far more complicated than any of us can conceive, thus sometimes the simplest model just isn’t the correct one.

---

Praise For Occams Razor

Albert Einstein

“It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience.”

“Everything should be made as simple as possible, but not simpler.”

Stephen Hawking

"We could still imagine that there is a set of laws that determines events completely for some supernatural being, who could observe the present state of the universe without disturbing it. However, such models of the universe are not of much interest to us mortals. It seems better to employ the principle known as Occam’s razor and cut out all the features of the theory that cannot be observed."

Isaac Newton

"We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.”

---

Applying Occams Razor

---

Return to: How To Think